Most widely available lossless format for documents?

ZT
Posted By
Zarbol Tsar
Jan 27, 2005
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2147
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88
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Closed
Which lossless graphics file format is most likely to be readable by the majority of computers users?

WHAT HAPPENED THIS TIME

I recently had to email a scan of a ‘typed’ letter to someone. I figured that GIF was a good choice because I figured it is almost universally readable and it was lossless. However the recipient said they could not open it!

(I don’t know what software they were running. The recipient worked as a local government employee and they did not know what software they had got either.)

PREPARING FOR NEXT TIME

I want to be able to send graphics to minimize the chance that users saying can’t open my file. I can scan to pretty much any graphics file format, so all I need to do is make an informed choice. Ha!

Very surprisingly, I found that (lossy) JPEG at 200 dpi gave me a graphics file that was not too huge and was much more readable than I had expected. For the sake of commonality and universality and readablility, I re-sent my graphics using JPEG. But somehow JPEG doesn’t really feel right for typed documents.

Somewhere on the web I read that PNG was almost universally readable. Is this really so? Would it be a good choice for all emailed scans?

Can someone please advise.
Thank you.

MacBook Pro 16” Mockups 🔥

– in 4 materials (clay versions included)

– 12 scenes

– 48 MacBook Pro 16″ mockups

– 6000 x 4500 px

J
jjs
Jan 27, 2005
"Zarbol Tsar" wrote in message
Which lossless graphics file format is most likely to be readable by the majority of computers users?

(I don’t know what software they were running. The recipient worked as a local government employee and they did not know what software they had got either.)

PREPARING FOR NEXT TIME

You can prepare all you want, but if you have incompetents receiving the images, then you are at the mercy of their ignorance.

Somewhere on the web I read that PNG was almost universally readable. Is this really so? Would it be a good choice for all emailed scans?

PNG is a disaster for Micro$oft product users. Even PowerPoint can create it and not display it properly for it’s own sake!
T
toby
Jan 27, 2005
TIFF comes to mind. Viewers are generally standard equipment.
AV
adam.verizon
Jan 27, 2005
Have him open the GIF file in his web browser, they can all display this file type. If he says it will not, then something is wrong with the way the computer is set up (either that or he has images disabled in his browser, and that is either company policy or his own fault).
JM
John McWilliams
Jan 27, 2005
toby wrote:
TIFF comes to mind. Viewers are generally standard equipment.
That would be wrong. JPEG is far more common.


john mcwilliams

I know that you believe you understood what you think I said, but I’m not sure you realize that what you heard is not what I meant.
JB
Jonathan Bartlett
Jan 27, 2005
Zarbol Tsar wrote:
Which lossless graphics file format is most likely to be readable by the majority of computers users?

PDF. There is a lossless and lossy way for PDF to encode images. Make sure it is doing it lossless. Other than that, GIF is your best bet. Either you made a bad GIF or the person viewing it was an idiot.

What program did you make the GIF with? Could Internet Explorer open it? If so, then they were probably just too stupid to see anything you send them.

Jon
DW
Dances With Crows
Jan 27, 2005

[ Crossposting trimmed ]
["Followup-To:" header set to comp.periphs.scanners.] On Thu, 27 Jan 2005 12:40:54 -0800, John McWilliams staggered into the Black Sun and said:
toby wrote:
TIFF comes to mind. Viewers are generally standard equipment.
That would be wrong. JPEG is far more common.

? ‘Doze9x, 2K, and XP include "Kodak Imaging", which can display G4, uncompressed, and LZW TIFFs. OS X includes a TIFF viewer. Unix-like OSes have ImageMagick, xv, Kuickshow, and Eye Of GNOME, which can all handle all common image formats including TIFF in all normally-used compression formats.

If you meant "JPEG images are more common on the WWW", that’s true–but that’s because the average Web browser doesn’t display TIFF for historical raisins. In general, you need to remember that JPEG is lossy and therefore not suitable for some of the things that people need to do with their images. JPEG works for viewing over the Net because lossy compression means smaller file sizes, which the poor bastards stuck on dialup like.


Matt G|There is no Darkness in eternity/But only Light too dim for us to see Hire me! http://crow202.dyndns.org/~mhgraham/resume/
The early bird who catches the worm works for someone who comes in late and owns the worm farm. –Travis McGee
BN
Bob Niland
Jan 27, 2005
Zarbol Tsar wrote:

Which lossless graphics file format is most likely to
be readable by the majority of computers users?

PDF using only LZW compression. Of course, many real-world contone images compress poorly, or not at all, with LZW, in which case you’ll need to consider the JPG tradeoffs.

If the source image happens to be vector (e.g. .AI, .DWG, .DXF, ..EPS, .SVG), a carefully considered workflow can preserve the vector data structures in the resulting PDF.


Regards, Bob Niland mailto:
http://www.access-one.com/rjn email4rjn AT yahoo DOT com NOT speaking for any employer, client or Internet Service Provider.
BH
Bill Hilton
Jan 27, 2005
Which lossless graphics file format is most likely to be readable by the majority of computers users?

8 bit tiff with no compression would get my vote, if you insist on "lossless". If you can accept a lossy format, then jpegs.
BH
Bill Hilton
Jan 27, 2005
TIFF comes to mind. Viewers are generally standard equipment

John McWilliams wrote …

That would be wrong. JPEG is far more common
He did specify "lossless", which eliminates vanilla jpegs.
BN
Bob Niland
Jan 28, 2005
Bill Hilton wrote:

He did specify "lossless", which eliminates vanilla jpegs.

Which to my mind also rules out GIF for color documents, since it’s 8-bit. Might be OK for B&W and grayscale, but crushing the color depth is easily as damaging as
imposing a curve-matching compression like JPG.

GIF also has no notion of "dpi", although the general convention is that it’s a very coarse 72 dpi. If you
want to share even at FAX res (200 dpi), by default
the document page will seem to be way too big.

GIF, JPG and TIF are also (usually) single-page file
formats.

I once got sent a single file that was a multi-page TIFF (from a company that at the time was refusing to
acknowledge the existence of PDF). Took a while to
figure out how to see pages other than 1.


Regards, Bob Niland mailto:
http://www.access-one.com/rjn email4rjn AT yahoo DOT com NOT speaking for any employer, client or Internet Service Provider.
Jan 28, 2005
Zarbol Tsar wrote:

Which lossless graphics file format is most likely to be readable by the majority of computers users?
[…]
Somewhere on the web I read that PNG was almost universally readable. Is this really so? Would it be a good choice for all emailed scans?

No. Especially on older setups, PNG won’t work. I read the other responses (PDF, TIFF… etc) but still, GIF is the best choice, with one caveat: Avoid all bit depths other than 256 for maximum compatibility (and no transparency or multiple images of course). Even some recent software has major problems with 2 bps GIFs (Acrobat being one of them, I believe). Other than that, any (non-ideologically oriented) program that can read PNGs will read GIFs. PDF is too recent and needs a plugin (and anybody who installed acroread will likely have a recent browser capable of reading GIFs), TIFF may or may not be well supported (there just are too many variations and it’s a complex format). JPEG (vanilla, not 2000) is actually the best choice if you ask me, even better than GIF, if not text quality but compatibility is the most imprortant criteria.
J
jjs
Jan 28, 2005
"Bob Niland" wrote in message

GIF also has no notion of "dpi", although the general convention is that it’s a very coarse 72 dpi.

Neither do I. What is dpi? What does a coarse dpi look like, and why should I care?
BN
Bob Niland
Jan 28, 2005
GIF also has no notion of "dpi", although the general convention is that it’s a very coarse 72 dpi.

jjs wrote:
Neither do I. What is dpi?

Dots Per Inch. Fax on "quality" setting is usually 200 dpi. Inkjet and laser printers nowadays start
at 300 dpi, although 600 dpi for black is considered
the minimum. "Publication quality" is 2400 dpi or so.

72 dpi is the very low-end of monitor resolution
these days. But monitors can do 24 bits of depth per
pixel. GIF can’t.

What does a coarse dpi look like, and why should I care?

Most raster graphics file formats, in addition to being
an array of X by Y pixel data values, encode what
real-world dimensions the span of X and Y are intended
to represent.

GIF does not, and the default assumption is 72 dpi.
Unless the receiving/rendering app is smart enough to
ask the user (and rescale), any GIF raster bigger than
about 576 x 756 won’t print properly on US letter size
(allowing for some unprintable margin area).

So if you scan the 8×10.5 region of a letter-size
document at 300 dpi, you’ll get a 2400 x 3150 raster.
If you save it as GIF, a "dumb" (and maybe not so dumb) receiving app may think it’s supposed to print
that at 33.33 x 43.75 inches.

I just ran this experiment in Photoshop 7.0. Created
a 300 dpi 8×10.5 image. Saved it as .GIF. When it
re-opened, Photoshop thought it was a 33×44 inch image,
and would have attempted to print it at that size.

Unless 72 dpi is ideal for the subject matter, using
..GIF will cause extra work for recipients of the files, when they attempt to print them.


Regards, Bob Niland mailto:
http://www.access-one.com/rjn email4rjn AT yahoo DOT com NOT speaking for any employer, client or Internet Service Provider.
J
jjs
Jan 28, 2005
"Bob Niland" wrote in message
GIF also has no notion of "dpi", although the general convention is that it’s a very coarse 72 dpi.

jjs wrote:
Neither do I. What is dpi?

Dots Per Inch.

Gee, I just consider pixels x pixels and have never gone wrong. I guess dpi is for the mathematically disadvantaged.
JM
John McWilliams
Jan 28, 2005
Bill Hilton wrote:
TIFF comes to mind. Viewers are generally standard equipment

John McWilliams wrote …

That would be wrong. JPEG is far more common

He did specify "lossless", which eliminates vanilla jpegs.
It surely does; overlooked the word "lossless" in the Subject and responded only to what’s most generally viewable, thinking a JPG would almost certainly be an improvement over a GIF, and if converted to TIFF would be too big to send.


John McWilliams
AM
Andrew Morton
Jan 28, 2005
Which to my mind also rules out GIF for color documents, since it’s 8-bit.

Of course, if the original has less than 257 unique colours then GIF would suffice.

However, text should be saved as text – an OCR program can translate an image-of-text into text.

Andrew
L
LQQK
Jan 28, 2005
As a 20 year manager I will say this: The sender is the problem. By his own admission, he sent something the person on the other end could not open. The sender must realize that the recipient may be "professionally handicapped" – but not necessarily "stupid". As you explain, the image should have been "tested in the browser" by the sender. Before sending them to their final destination, I frequently email the messages to my self to test their viability – by viewing them with IE (the ultimate hurdle – it which normally lies supposedly dormant but ever eager to rear its ugly head) instead of my glorious Firefox browser..

On Thu, 27 Jan 2005 16:13:35 -0500, Jonathan Bartlett
wrote:

What program did you make the GIF with? Could Internet Explorer open it? If so, then they were probably just too stupid to see anything you send them.

Jon
HB
Hans-Bernhard Broeker
Jan 28, 2005

[Please, if you do have to crosspost, next time at least be so kind as
to set a single-group followup-to. Repaired.]

In comp.graphics.algorithms Zarbol Tsar wrote:
Which lossless graphics file format is most likely to be readable by the majority of computers users?

Your initial choice of GIF (if and as far as it *is* lossless, for the given image) was quite certainly the right answer to that already. In a nutshell, no program that is capable of displaying images at all, and is younger than, roughly, the original Mosaic browser, could seriously refuse working with GIF files.

However the recipient said they could not open it!

If so, then odds are that no other choice of file format would have worked any better.

The recipient rather clearly either doesn’t know how to extract and view non-text attachments found in emails at all, regardless of what format they come in, or he’s under some external restriction preventing him from doing so (e.g. a completely brain-dead email client being forced on him, or a system security measure blocking all attachments summarily).


Hans-Bernhard Broeker ()
Even if all the snow were burnt, ashes would remain.
ZT
Zarbol Tsar
Jan 28, 2005
On 28 Jan 2005, Bob Niland wrote:

GIF also has no notion of "dpi", although the general convention is that it’s a very coarse 72 dpi.

jjs wrote:
Neither do I. What is dpi?

Dots Per Inch. Fax on "quality" setting is usually 200 dpi. Inkjet and laser printers nowadays start
at 300 dpi, although 600 dpi for black is considered
the minimum. "Publication quality" is 2400 dpi or so.
72 dpi is the very low-end of monitor resolution
these days. But monitors can do 24 bits of depth per
pixel. GIF can’t.

— snip —

Bob, I am the OP and am interested in looking closer at TIFF.

When I go to create a TIFF using ACDSee 3.1 I get the following options *before* the TWAIN menu appears. Presumably these parameters are pass to the TWAIN software?

Compression:
CCITT Group 3
CCITT Group 3
LZW
Deflate
JPEG

Resolution
horizontal – default is 96 dpi
vertical – default is 96 dpi

What should I select from the above to get:
(a) the most compact resultant TIFF file?
(b) the most common compression in order that most users can read the TIFF file?

Are the horizontal/vertical resolution options above going to ‘re- resolve’ whatever I select in the TWAIN menu? For example, the TWAIN software defaults to 300 dpi so will TWAIN create a file with a resoultion of 300 dpi and then ACDSee recreate this file as a TIFF with, say, 96 dpi? Seems a recipe for poor quality!

Any info welcome.
ZT
Zarbol Tsar
Jan 28, 2005
On 27 Jan 2005, Bill Hilton wrote:

Which lossless graphics file format is most likely to be readable by the majority of computers users?

8 bit tiff with no compression would get my vote, if you insist on "lossless". If you can accept a lossy format, then jpegs.

Hello Bill, I just replied to this thread saying that I have the following options when I create a TIFF using ACDSee 3. I do not have anything for 8 bit. Should I use some other applicatin than ACDSee 3 or will TIFF usually be 8 bit?

Compression:
CCITT Group 3
CCITT Group 3
LZW
Deflate
JP EG

Resolution
horizontal …. (dpi)
vertical … (dpi)
DW
Dances With Crows
Jan 28, 2005

[ Crossposting trimmed ]
["Followup-To:" header set to comp.periphs.scanners.] On Fri, 28 Jan 2005 14:29:08 GMT, Zarbol Tsar staggered into the Black Sun and said:
On 28 Jan 2005, Bob Niland wrote:
GIF also has no notion of "dpi", although the general convention is that it’s a very coarse 72 dpi.
jjs wrote:
Neither do I. What is dpi?
Dots Per Inch. Fax on "quality" setting is usually 200 dpi. Inkjet and laser printers nowadays start at 300 dpi, although 600 dpi for
When I go to create a TIFF using ACDSee 3.1 I get the following options *before* the TWAIN menu appears. Presumably these parameters are [passed] to the TWAIN software?

Not quite. I’d guess only the "resolution" setting gets passed to the scanner itself, and the scanner delivers a raw bitmap scanned at X by Y DPI. The "compression" setting is applied to the raw bitmap when you save the file.

Compression:
CCITT Group 3, CCITT Group 3, LZW, Deflate, JPEG

? Did you make a typo here? I’d guess that one of these was "Group 4", ’cause it doesn’t make sense for Group 3 to be listed twice.

Resolution
horizontal – default 96 dpi vertical – default 96 dpi

What should I select from the above to get:
(a) the most compact resultant TIFF file?

You need to ask "Which resolution and color depth should I scan at?" first. The answer to that question depends on your final use for the images. If you say, "I am going to use these images for $FOO", then someone will be able to advise you. The smallest TIFFs result from low resolution black-and-white scans compressed with Group4. The smallest TIFFs in grayscale/color result from low resolution scans compressed with LZW.

(b) the most common compression in order that most users can read the TIFF file?

This question has been addressed several times already. Well, I’ll repeat myself: Deflate is inefficient and not everything understands it, so forget it. G3 is inefficient compared to G4, so forget it. Not many programs understand JPEG-TIFF right now, so forget it.

That leaves G4 and LZW. Use LZW for grayscale or color. Use G4 for black-and-white. ‘Doze XP, 2K, 9x, and even NT 4 came with "Kodak Imaging", which can read G4 and LZW TIFFs without a problem. OS X has a TIFF-viewer built in, which understands G4 and LZW. Unix-like OSes have ImageMagick, xv, Kuickshow, and Eye Of GNOME, all of which understand every common image format including G4 and LZW TIFFs. That covers all the OSes you’re likely to run into, so there’s no problem with the image-viewing software.

If the people you’re sending images to have no idea what to open a TIFF with, tell them "Start->Programs->Accessories->Imaging" if they’re using ‘Doze. You shouldn’t have to educate people like that, but dumb people and misconfigured ‘Doze machines are endemic problems.


Matt G|There is no Darkness in eternity/But only Light too dim for us to see Hire me! http://crow202.dyndns.org/~mhgraham/resume/
That which does not kill us makes us stranger. –Trevor Goodchild
AV
adam.verizon
Jan 28, 2005
not really, when you consider that this is how all printers are measured, mainly so the printer manufacturers can gauge how much ink will be required to print X number of pages at Xdpi (with the notable exception of Laser Printers and other "toner" based products) For instance a document in, say, Photoshop, is measured at 300 dpi, and also 8.5"x11", the dimensions of the document in pixels will be widly different than a document at a lower dpi say, 200 with the same print dimensions.
BH
Bill Hilton
Jan 28, 2005
8 bit tiff with no compression would get my vote, if you insist on "lossless". If you can accept a lossy format, then jpegs.

Zarbol Tsar writes …

Hello Bill, I just replied to this thread saying that I have the following options when I create a TIFF using ACDSee 3. I do not have anything for 8 bit.

Hi Zarbol, if they don’t give you a choice in the menu then it’s almost certainly 8 bit/channel, unless your input was 16 bit. Easy way to check is to generate a file and open it in Photoshop and do Image > Mode and see whether 8 bits/chanel or 16 bits/channel is checked.

Compression:
LZW
Deflate
JPEG

Non-jpeg compression of tiffs is lossless and will make it smaller (generally 30-60% the original file size, on the type of files I shoot) but will make it less likely that the recepient can open it easily. Jpeg is not lossless but a high-quality jpeg should be about 1/3 or so the size of the original (and a highly compressed one often 1/20th of so the byte count of the original) and will still have pretty good quality for most needs. You can always send jpegs and if they want a high rez version of a particular file send them that later. This is how a lot of magazine submissions are done these days and what I’d do unless you knew they HAD to have tiffs and had a non-dial up connection to handle the long download times.

Bill
J
jjs
Jan 28, 2005
"Jonathan Bartlett" wrote in message

PDF. There is a lossless and lossy way for PDF to encode images. Make sure it is doing it lossless. Other than that, GIF is your best bet.

GIF is not lossless! If you have more than 255 colors, it loses colors!
J
jjs
Jan 28, 2005
"Adam.Verizon" wrote in message
not really, when you consider that this is how all printers are measured, mainly so the printer manufacturers can gauge how much ink will be required to print X number of pages at Xdpi (with the notable exception of Laser Printers and other "toner" based products)

Nonsense. Pure nonsense. It’s pixels and that’s all there is to it.
BH
Bill Hilton
Jan 28, 2005
Nobody writes …

GIF is the best choice

Not really …

with one caveat: Avoid all bit depths other than 256 for maximum compatibility

A "bit depth" of 256 would indeed do the trick. Unfortunately GIF’s bit depth is only 8 bits, limiting you to 256 gradations or colors. By comparison jpegs are 8 bits/channel with three channels, so 24 bits total, giving you over 16 million colors.

This is why gifs are best suited for line art or cartoons or images with few colors and why jpegs are better for true color, like in photo images.
J
jjs
Jan 28, 2005
"Bill Hilton" wrote in message
Nobody writes …

GIF is the best choice

Not really …

with one caveat: Avoid all bit depths other than 256 for maximum compatibility

A "bit depth" of 256 would indeed do the trick.

Yeah, that’s what we need is a 255bit word.
R
RSD99
Jan 28, 2005
"Bill Hilton" stated:
"…
Unfortunately GIF’s bit depth is only 8 bits, limiting you to 256 gradations or colors
…."

However … and I don’t think that anyone has mentioned this yet … GIF files can be saved with either a fixed palette, or using the so-called "Adaptive Palette." If the image file is saved with one of the fixed palettes (such as the "Windows Palette"), it may have (for example) something like only six levels of gray, and so forth!

GIF is somewhat deceptive, and almost always destructive in some way. Particularly with continuous tone (photographic) images. Best to avoid unless it is absolutely necessary (such as "for the web").
G
gruhn
Jan 28, 2005
This is why gifs are best suited for line art or cartoons or images with few colors and why jpegs are better for true color, like in photo images.

Don’t forget edge handling ability.
T
toby
Jan 28, 2005
John McWilliams wrote:
toby wrote:
TIFF comes to mind. Viewers are generally standard equipment.
That would be wrong. JPEG is far more common.

Au contraire. OS X and Windows have multiformat viewers (incl varieties of single & multipage TIFF) as standard. And of course, TIFF viewers are available (often standard) in all varieties of Linux.

–Toby


john mcwilliams

I know that you believe you understood what you think I said, but I’m not sure you realize that what you heard is not what I meant.
Jan 29, 2005
"Bill Hilton" wrote:
Nobody writes …

GIF is the best choice

Not really …

with one caveat: Avoid all bit depths other than 256 for

^^^ missing "colors"

maximum compatibility

A "bit depth" of 256 would indeed do the trick. Unfortunately GIF’s bit depth is only 8 bits, limiting you to 256 gradations or colors. By comparison jpegs are 8 bits/channel with three channels, so 24 bits total, giving you over 16 million colors.

This is why gifs are best suited for line art or cartoons or images with few colors and why jpegs are better for true color, like in photo images.

Which makes it a good choice for what the poster asked (text, not full color photos).
Jan 29, 2005
"Andrew Morton" wrote:

Which to my mind also rules out GIF for color documents, since it’s 8-bit.

Of course, if the original has less than 257 unique colours then GIF would suffice.

However, text should be saved as text – an OCR program can translate an image-of-text into text.

Really? If it’s handwritten? Mathematical equations? Different language?
C
CSM1
Jan 29, 2005
"nobody" wrote in message
"Bill Hilton" wrote:
Nobody writes …

GIF is the best choice

Not really …

with one caveat: Avoid all bit depths other than 256 for

^^^ missing "colors"

maximum compatibility

A "bit depth" of 256 would indeed do the trick. Unfortunately GIF’s bit depth is only 8 bits, limiting you to 256 gradations or colors. By comparison jpegs are 8 bits/channel with three channels, so 24 bits total, giving you over 16 million colors.

This is why gifs are best suited for line art or cartoons or images with few colors and why jpegs are better for true color, like in photo images.

Which makes it a good choice for what the poster asked (text, not full color photos).
The whole problem of not being able to open a graphic file can be solved very easily by installing the free Irfanview program and plug-ins. Irfanview will open about every image or graphic file format, currently known. http://www.irfanview.com

The best lossless graphic file format and most widely used is TIFF. TIFF will do B&W(bitmap), 8 bit or 16 bit gray scale and full color.


CSM1
http://www.carlmcmillan.com
C
CSM1
Jan 29, 2005
"CSM1" wrote in message
"nobody" wrote in message
"Bill Hilton" wrote:
Nobody writes …

GIF is the best choice

Not really …

with one caveat: Avoid all bit depths other than 256 for

^^^ missing "colors"

maximum compatibility

A "bit depth" of 256 would indeed do the trick. Unfortunately GIF’s bit depth is only 8 bits, limiting you to 256 gradations or colors. By comparison jpegs are 8 bits/channel with three channels, so 24 bits total, giving you over 16 million colors.

This is why gifs are best suited for line art or cartoons or images with few colors and why jpegs are better for true color, like in photo images.

Which makes it a good choice for what the poster asked (text, not full color photos).
The whole problem of not being able to open a graphic file can be solved very easily by installing the free Irfanview program and plug-ins.
Irfanview
will open about every image or graphic file format, currently known. http://www.irfanview.com

The best lossless graphic file format and most widely used is TIFF. TIFF will do B&W(bitmap), 8 bit or 16 bit gray scale and full color.

CSM1
http://www.carlmcmillan.com
TIFF will also do multiple pages.

Jpeg is a lossy format and great for web pictures, which may be the most popular image format used.


CSM1
http://www.carlmcmillan.com
G
gamma-ray
Jan 29, 2005
JPEG is *excellent* for text and line art. But only if used with the proper sampling factors (1×1, not the default 2×1). More info on my page: http://www.redrival.com/scorpius

Compare these two images and you will see that the jpg is indistinguishable from the png:
http://home.comcast.net/~gamma-ray/text.png
http://home.comcast.net/~gamma-ray/text.jpg

In this case, jpeg is effectively lossless.
G
gamma-ray
Jan 30, 2005
Compare these two images and you will see that the jpg is indistinguishable from the png:
http://home.comcast.net/~gamma-ray/text.png
http://home.comcast.net/~gamma-ray/text.jpg

I forgot to mention that the above screen shots were made on an LCD display, with cleartype turned on. So, they will look very blurry on CRTs.
G
gruhn
Jan 31, 2005
I forgot to mention that the above screen shots were made on an LCD
display,

Don’t worry, it was self evident. Of course, it tends to break the validity of the test…
DL
Donald Link
Feb 1, 2005
On Sun, 30 Jan 2005 18:38:07 -0500, "Anthony D’Agostino" wrote:

Compare these two images and you will see that the jpg is indistinguishable from the png:
http://home.comcast.net/~gamma-ray/text.png
http://home.comcast.net/~gamma-ray/text.jpg

I forgot to mention that the above screen shots were made on an LCD display, with cleartype turned on. So, they will look very blurry on CRTs.
I do not know what crt you are using but my Sun Microsystem PC monitor with a Sony tube displays them better than what the LCD does.
AM
Andrew Morton
Feb 10, 2005
However, text should be saved as text – an OCR program can translate an image-of-text into text.

Really? If it’s handwritten? Mathematical equations? Different language?

Yes. Handwriting is nearer to a drawing, so I wouldn’t count that unless only the text itself needs to be recorded. There are plenty of markup languages for equations. In what way might a different language be a problem? More information can be gleaned from a text file with language settings in it than from an image, for example if I were editing something flagged as being in English then I would know to spell colour as colour whereas if it were flagged as American English I would spell colour as color.
Getting a bit off-topic for this newsgroup.

Andrew
D
dkcombs
Feb 23, 2005
Allow me to to ask some surely-naive questions —
most probably answerable via an integer divide
mandated to have no remainder, or something
similar. But I was never any good at
being able to follow (understand) where books
would say thing like:

The reader can fill in the obvious steps.

…, which by elementary algebra simplifies to …

… , which is clearly equivalent to a divide by zero.

So I’ll be asking you to show the elided steps:

….
Most raster graphics file formats, in addition to being
an array of X by Y pixel data values, encode what
real-world dimensions the span of X and Y are intended
to represent.

GIF does not, and the default assumption is 72 dpi.
Unless the receiving/rendering app is smart enough to
ask the user (and rescale),

Ask the user what?

And then rescale to what, and why?

any GIF raster bigger than
about 576 x 756 won’t print properly on US letter size

Why not? Could you show enough so that I can myself
do similar calculations and deductions for other such
situations. Thanks.

(allowing for some unprintable margin area).

So where does this get done, what part of the
math handles this?

So if you scan the 8×10.5 region of a letter-size
document at 300 dpi, you’ll get a 2400 x 3150 raster.

A "raster" being what, a rectangle of pixels considered by the printer software/hardware as being a single
print-level item?

If you save it as GIF, a "dumb" (and maybe not so dumb) receiving app may think it’s supposed to print
that at 33.33 x 43.75 inches.

Why might it think this?

In what way would a "smarter" app come to a different conclusion, and how?

I just ran this experiment in Photoshop 7.0. Created
a 300 dpi 8×10.5 image. Saved it as .GIF. When it
re-opened, Photoshop thought it was a 33×44 inch image,

… because …

and would have attempted to print it at that size.

Workaround?

Unless 72 dpi is ideal for the subject matter,

(such as?)

using
.GIF will cause extra work for recipients of the files,
when they attempt to print them.

Thanks!

David
C
CSM1
Feb 23, 2005
Comments in body.

"David Combs" wrote in message
Allow me to to ask some surely-naive questions —
most probably answerable via an integer divide
mandated to have no remainder, or something
similar. But I was never any good at
being able to follow (understand) where books
would say thing like:

The reader can fill in the obvious steps.

…, which by elementary algebra simplifies to …

… , which is clearly equivalent to a divide by zero.

So I’ll be asking you to show the elided steps:


Most raster graphics file formats, in addition to being
an array of X by Y pixel data values, encode what
real-world dimensions the span of X and Y are intended
to represent.

GIF does not, and the default assumption is 72 dpi.
Unless the receiving/rendering app is smart enough to
ask the user (and rescale),

Ask the user what?
What DPI to print the image at.

The final printed size depends on the pixel dimensions and the resolution the printer is set to.

The math is:
Horizontal pixels divided by printer dpi setting = the inches of the printed image in the horizontal dimension.

Vertical pixels divided by printer dpi setting = the inches of the printed image in the vertical dimension.

A 2400 horizontal pixel by 3000 vertical pixel image will produce a 8 inch by 10 inch print on the paper when the printer resolution is set to 300 dpi.
2400/300=8
3000/300=10

And then rescale to what, and why?

any GIF raster bigger than
about 576 x 756 won’t print properly on US letter size

Why not? Could you show enough so that I can myself
do similar calculations and deductions for other such
situations. Thanks.

(allowing for some unprintable margin area).

So where does this get done, what part of the
math handles this?

The unprintable margin area varies with the specific printer, it is the clos est to the edge that a specific printer is capable to printing on the paper.

For my HP 712 the minimum margin is 0.25 inches on the right and left margins and 0.04 inches on the top and 0.46 inches on the bottom when using letter size paper.

You have to look up the specifications on your printer to find the minimum margins.

You subtract the minimum margins of your printer from the paper size to find what the maximum image size that can be printed with your printer.

For the HP 712 the maximum size I can print on letter size paper is 8.0 inches by 10.5 inches.
So if you scan the 8×10.5 region of a letter-size
document at 300 dpi, you’ll get a 2400 x 3150 raster.

A "raster" being what, a rectangle of pixels considered by the printer software/hardware as being a single
print-level item?
A "raster" being the actual image. A raster is the square dots that make up the image. They are arranged in a rectangle H dots wide by V dots high.

If you save it as GIF, a "dumb" (and maybe not so dumb) receiving app may think it’s supposed to print
that at 33.33 x 43.75 inches.

Why might it think this?

In what way would a "smarter" app come to a different conclusion, and how?

I just ran this experiment in Photoshop 7.0. Created
a 300 dpi 8×10.5 image. Saved it as .GIF. When it
re-opened, Photoshop thought it was a 33×44 inch image,

… because …
Gif does not record the dpi in the header of the image file. Gif only records the horizontal and vertical dimensions of the image and the color information.

and would have attempted to print it at that size.

Workaround?

Unless 72 dpi is ideal for the subject matter,

(such as?)
An arbitrary value chosen by just about everybody that writes image software for Windows.

using
.GIF will cause extra work for recipients of the files,
when they attempt to print them.

Thanks!

David

CSM1
http://www.carlmcmillan.com
J
jjs
Feb 23, 2005
"CSM1" wrote in message

Ask the user what?
What DPI to print the image at.

I never heard of DPI metric stored in an image, and if it is there, it’s just a handy metric for those who don’t understand that pixels-is-pixels.
G
gruhn
Feb 23, 2005
I never heard of DPI metric stored in an image, and if it is there, it’s just a handy metric for those who don’t understand that pixels-is-pixels.

Agree re: pixels, don’t agree re: just.

If you scan something in, it has a definite "actual size". DPI is a way to save that info. Shirley there are people and applications who find that far handier than getting an image and guessing. Or storing the size in the file name. Or…
T
toby
Feb 24, 2005
jjs wrote:
"CSM1" wrote in message

Ask the user what?
What DPI to print the image at.

I never heard of DPI metric stored in an image,

I’m not sure what you mean. Many image formats — from TIFF all the way down through BMP — have header fields specifically defined for resolution info, and these are usually put to good use. In addition, Photoshop typically uses whatever "application specific" data is provided for in order to record its own "image resource" metadata, which invariably includes resolution (and units).

Some images don’t have meaningful physical dimensions (e.g. digital camera grabs); but many do (e.g. scans).

and if it is there, it’s
just a handy metric for those who don’t understand that
pixels-is-pixels.

They also have pixel counts, of course.
J
jjs
Feb 24, 2005
"gruhn" wrote in message
I never heard of DPI metric stored in an image, and if it is there, it’s just a handy metric for those who don’t understand that pixels-is-pixels.

Agree re: pixels, don’t agree re: just.

If you scan something in, it has a definite "actual size". DPI is a way to save that info. Shirley there are people and applications who find that far
handier than getting an image and guessing. Or storing the size in the file
name. Or…

Or being smart.
G
gruhn
Feb 24, 2005
Or being smart.

Explain how "just guessing wrong" is "smart."
J
jjs
Feb 24, 2005
"gruhn" wrote in message
Or being smart.

Explain how "just guessing wrong" is "smart."

Guessing isn’t neccessary; understanding simple arithmetic is smart enough.
G
gruhn
Feb 24, 2005
Guessing isn’t neccessary; understanding simple arithmetic is smart
enough.

We’re not having the same conversation as each other.
H
Hecate
Feb 25, 2005
On 23 Feb 2005 17:16:40 -0800, "toby"
wrote:

Some images don’t have meaningful physical dimensions (e.g. digital camera grabs); but many do (e.g. scans).
All images have physical dimensions. On a computer they’re expressed as pixels. On a print the resolution is expressed as dpi. The dpi is completely immaterial as far as an image on a computer is concerned.



Hecate – The Real One

veni, vidi, reliqui
T
toby
Feb 25, 2005
Hecate wrote:
On 23 Feb 2005 17:16:40 -0800, "toby"
wrote:

Some images don’t have meaningful physical dimensions (e.g. digital camera grabs); but many do (e.g. scans).
All images have physical dimensions. On a computer they’re expressed as pixels. On a print the resolution is expressed as dpi. The dpi is completely immaterial as far as an image on a computer is concerned.

A pixel count is dimensionless. The resolution value gives a pixel a physical scale. There’s really nothing to discuss here – this is all taken as read.



Hecate – The Real One

veni, vidi, reliqui
G
gruhn
Feb 25, 2005
A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions go.

The resolution value gives a pixel a physical scale

That’s true. But "dimension" needn’t by "real world."

There’s really nothing to discuss here – this is all
taken as read.

I wrote nothing above.
T
toby
Feb 25, 2005
gruhn wrote:
A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions go.

It’s a count. It’s also dimensionless. It’s a purely terminological point. There is no misunderstanding between us, except I was originally responding to a strange assertion from jjs. Any further debate on this is a waste of time.

The resolution value gives a pixel a physical scale

That’s true. But "dimension" needn’t by "real world."
There’s really nothing to discuss here – this is all
taken as read.

I wrote nothing above.

I was responding to Hecate.
KM
Kennedy McEwen
Feb 25, 2005
In article <HfATd.78$>, gruhn
writes
A pixel count is dimensionless

No. Pixel is a valid unit.

I think you mean "Yes. Pixel is a valid unit". Being dimensionless does not preclude something from being a unit. —
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when replying)
HB
Hans-Bernhard Broeker
Feb 25, 2005
In comp.graphics.algorithms Hecate wrote:

All images have physical dimensions.

Not all — not in the usual meaning of a "physical" dimension.

On a computer they’re expressed as pixels.

A pixel is *not* a physical dimension. It’s a purely abstract one. The physical size of an actual pixel is a design parameter of a computer’s display. It differs from machine to machine.

On a print the resolution is expressed as dpi. The dpi is completely immaterial as far as an image on a computer is concerned.

Not quite. It can be material or not, depending on where the image currently is. While it’s being displayed on the screen, the DPI resolution of that screen becomes the DPI of the image displayed. If the image is not visible, it is can be immaterial whether it has an associated DPI value or not — but if it does have one, that means that on displaying it on a physical medium, you have a choice to make: whether to match pixel counts, or physical size of the image.

E.g. a 600×600 pixel input scanned at 300 DPI is, physically, 2 inches squared. But a computer’s monitor has a lot less than 300 DPI — let’s say it’s 100. So how to display the image: at 600×600 pixels, which would make it 6 x 6 inches, or at 2×2 inches, downsampling it to 200×200 pixels in the process?

And then there’s images that never corresponded to a particular physical size anyone’s interested in — most prominently, digital camera shots. The image sensor in a digicam does, of course, have a physical size, and as such, the image acquired by it has a DPI value — but because it’s a projected 2D image of 3D real-world objects, the DPI value of the sensor is quite irrelevant. What you need to know in this case is the absolute pixel count, i.e. the number of pixels in the image. The DPI setting is interesting for the people designing the camera, though — it governs effects like susceptibility to electronic noise vs. optical signal strength, and indirectly, through the physical sensor size, decides how hard the job is for the optical engineers to make lenses for that camera.


Hans-Bernhard Broeker ()
Even if all the snow were burnt, ashes would remain.
J
jjs
Feb 25, 2005
"toby" wrote in message
gruhn wrote:
A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions go.

It’s a count. It’s also dimensionless. It’s a purely terminological point. There is no misunderstanding between us, except I was originally responding to a strange assertion from jjs. Any further debate on this is a waste of time.

There is no debate. You simply have a silly idea you cannot give up.
J
jjs
Feb 25, 2005
"toby" wrote in message
gruhn wrote:
A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions go.

It’s a count. It’s also dimensionless.

It is not dimensionless: it represents a value other than zero. If it were dimensionless then anything made of pixels could be compressed to infinity.
KM
Kennedy McEwen
Feb 25, 2005
In article , jjs
<john&#064@?.net.invalid> writes
"toby" wrote in message
gruhn wrote:
A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions go.

It’s a count. It’s also dimensionless.

It is not dimensionless: it represents a value other than zero. If it were dimensionless then anything made of pixels could be compressed to infinity.
Rubbish, there are plenty of dimensionless units. Gradient of a slope is one example most people encounter at an early age. If the slope increases 1ft in every 10ft then it has a gradient of 0.1ft/ft – the units cancel out and you have a dimensionless gradient of 10%. It is pretty clear to everyone learning to walk that a 5% gradient is half as steep as a 10% one!

Interest rates are another example – for every $10 you invest your bank will give you $1. Interest rate is 0.1 dollars per dollar, or 10% – no dimensions. You would be pretty pissed off if your bank then turned round and told you that they had infinitely compressed their interest rate and you were just getting back the $10 you invested!

Dimensionless units exist all over the place, just as dimensionless constants do – pi, e, etc.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when replying)
J
jjs
Feb 25, 2005
"Kennedy McEwen" wrote in message

Rubbish, there are plenty of dimensionless units. […] Dimensionless units exist all over the place, just as dimensionless constants do – pi, e, etc.

You are speaking of metrics. I was just having p(h)un. Have a Guinness on me.
T
Tacit
Feb 25, 2005
In jjs wrote:
I never heard of DPI metric stored in an image,

Almost all image formats include the pixel-per-inch information, because almost all image formats are designed to store images that can be used for printing, and any image destined for print (or other physical world output) must include not only the pixels but also some measure of how large the pixels are.

Take a TIFF file that is 1000 by 3000 pixels. Save it at 300 pixels per inch, then change the resolution without resampling so that it is 1000 by 3000 pixels and 72 pixels per inch and save it again. Both images contain absolutely bit-for-bit identical pixel information.

Now place both images in a page layout program such as QuarkXPress. One will print far larger than the other. Sam epixel information, but the TIFF file format stores the pixels AND the resolution.

File fo0rmats which do not record resolution information are few and far between, and are usually formats intended only for on-screen display (eg, GIF).

…and if it is there,
it’s just a handy metric for those who don’t understand that pixels- is-pixels.

It’s a metric for those who intend to do more than display an image on a fixed-pixel device such as a computer monitor. Remember, images don’t just get shown on video displays; sometimes, they get printed, too.
T
toby
Feb 25, 2005
Kennedy McEwen wrote:
In article , jjs
<john&#064@?.net.invalid> writes
"toby" wrote in message
gruhn wrote:
A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions
go.
It’s a count. It’s also dimensionless.

It is not dimensionless: it represents a value other than zero. If
it were
dimensionless then anything made of pixels could be compressed to
infinity.
Rubbish, there are plenty of dimensionless units. …

Thankyou Kennedy! I knew I didn’t invent the concept.

Half the confusion in this thread stems from the fact that the question: "How large is this image?" has two answers.
1. a dimensionless pixel count (commensurate with no real world
measure)
2. a physical size, by combining the pixel count with the resolution info.
Of course, for images that don’t have an associated resolution, the latter answer is not available.

I entered this thread to contradict jjs’s assertion that file formats do not encode resolution:
I never heard of DPI metric stored in an image
Seems he has some reading to do.

–Toby

Dimensionless units exist all over the place, just as dimensionless constants do – pi, e, etc.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when
replying)
G
gruhn
Feb 25, 2005
It’s a count. It’s also dimensionless.

I see what you’re saying. I see what I was saying. You’re right. I was on crack.
H
Hecate
Feb 26, 2005
On 24 Feb 2005 19:56:54 -0800, "toby"
wrote:

Hecate wrote:
On 23 Feb 2005 17:16:40 -0800, "toby"
wrote:

Some images don’t have meaningful physical dimensions (e.g. digital camera grabs); but many do (e.g. scans).
All images have physical dimensions. On a computer they’re expressed as pixels. On a print the resolution is expressed as dpi. The dpi is completely immaterial as far as an image on a computer is concerned.

A pixel count is dimensionless. The resolution value gives a pixel a physical scale. There’s really nothing to discuss here – this is all taken as read.
Of course it isn’t diemnsionless. It has a width and a height.



Hecate – The Real One

veni, vidi, reliqui
B
Brian
Feb 26, 2005
toby wrote:

Kennedy McEwen wrote:

In article , jjs
<john&#064@?.net.invalid> writes

"toby" wrote in message

gruhn wrote:

A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions

go.

It’s a count. It’s also dimensionless.

It is not dimensionless: it represents a value other than zero. If

it were

dimensionless then anything made of pixels could be compressed to

infinity.

Rubbish, there are plenty of dimensionless units. …

Thankyou Kennedy! I knew I didn’t invent the concept.

Half the confusion in this thread stems from the fact that the question: "How large is this image?" has two answers.
1. a dimensionless pixel count (commensurate with no real world
measure)
2. a physical size, by combining the pixel count with the resolution info.
Of course, for images that don’t have an associated resolution, the latter answer is not available.

I entered this thread to contradict jjs’s assertion that file formats do not encode resolution:

I never heard of DPI metric stored in an image

Seems he has some reading to do.

–Toby

Dimensionless units exist all over the place, just as dimensionless constants do – pi, e, etc.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when

replying)
Sorry to tell you this Toby, some image formats DO store resolution (ppi) information. Corel Photopaint does. If I have an image that is 1800 x 1200 pixels, I can save it as a 6" x 4" at 300ppi, and a 2nd copy as a 12" x 8" at 150dpi. I then import the 2 images into CorelDraw and one image is 4 times the size of the other (twice the height, twice the width) and both images are the same "pixel" size.

Brian.
T
toby
Feb 26, 2005
Brian wrote:
toby wrote:

Kennedy McEwen wrote:

In article , jjs
<john&#064@?.net.invalid> writes

"toby" wrote in message

gruhn wrote:

A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions

go.

It’s a count. It’s also dimensionless.

It is not dimensionless: it represents a value other than zero. If

it were

dimensionless then anything made of pixels could be compressed to

infinity.

Rubbish, there are plenty of dimensionless units. …

Thankyou Kennedy! I knew I didn’t invent the concept.

Half the confusion in this thread stems from the fact that the question: "How large is this image?" has two answers.
1. a dimensionless pixel count (commensurate with no real world
measure)
2. a physical size, by combining the pixel count with the
resolution
info.
Of course, for images that don’t have an associated resolution, the latter answer is not available.

I entered this thread to contradict jjs’s assertion that file
formats
do not encode resolution:

I never heard of DPI metric stored in an image

Seems he has some reading to do.

–Toby

Dimensionless units exist all over the place, just as dimensionless constants do – pi, e, etc.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when

replying)
Sorry to tell you this Toby, some image formats DO store resolution (ppi) information. …

If you re-read the thread you’ll see that that is EXACTLY what I was trying to explain to someone else. These are the words I used:

"Many image formats — from TIFF all the way down through BMP — have header fields specifically defined for resolution info".

Brian.
B
Brian
Feb 26, 2005
toby wrote:

Brian wrote:

toby wrote:

Kennedy McEwen wrote:

In article , jjs
<john&#064@?.net.invalid> writes

"toby" wrote in message

gruhn wrote:

A pixel count is dimensionless

No. Pixel is a valid unit. W x H pixels is grand as dimensions

go.

It’s a count. It’s also dimensionless.

It is not dimensionless: it represents a value other than zero. If

it were

dimensionless then anything made of pixels could be compressed to

infinity.

Rubbish, there are plenty of dimensionless units. …

Thankyou Kennedy! I knew I didn’t invent the concept.

Half the confusion in this thread stems from the fact that the question: "How large is this image?" has two answers.
1. a dimensionless pixel count (commensurate with no real world
measure)
2. a physical size, by combining the pixel count with the

resolution

info.
Of course, for images that don’t have an associated resolution, the latter answer is not available.

I entered this thread to contradict jjs’s assertion that file

formats

do not encode resolution:

I never heard of DPI metric stored in an image

Seems he has some reading to do.

–Toby

Dimensionless units exist all over the place, just as dimensionless constants do – pi, e, etc.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when

replying)

Sorry to tell you this Toby, some image formats DO store resolution (ppi) information. …

If you re-read the thread you’ll see that that is EXACTLY what I was trying to explain to someone else. These are the words I used:
"Many image formats — from TIFF all the way down through BMP — have header fields specifically defined for resolution info".

Brian.
oops! I sometimes get confused as to who is saying what in here (being new to NG’s). My apologies Toby.

Brian
KM
Kennedy McEwen
Feb 26, 2005
In article , Hecate
writes
On 24 Feb 2005 19:56:54 -0800, "toby"
wrote:

Hecate wrote:
On 23 Feb 2005 17:16:40 -0800, "toby"
wrote:

Some images don’t have meaningful physical dimensions (e.g. digital camera grabs); but many do (e.g. scans).
All images have physical dimensions. On a computer they’re expressed as pixels. On a print the resolution is expressed as dpi. The dpi is completely immaterial as far as an image on a computer is concerned.

A pixel count is dimensionless. The resolution value gives a pixel a physical scale. There’s really nothing to discuss here – this is all taken as read.
Of course it isn’t diemnsionless. It has a width and a height.
Oh don’t get us started on that again! Pixels are abstract objects which do not have any intrinsic dimensions *until* they are physically rendered. If they had a fixed width and height, how would you explain the same image, with the same pixels, being printed at different sizes – special relativity?

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when replying)
M
MOP
Feb 26, 2005
Of course it isn’t diemnsionless. It has a width and a height.

Technically it is dimensionless when you write it you say 10 pixels (for example) that does not have physical size, 1 pixel could be a mm or a mile but would still be a pixel.
where as when it’s DPI it dots/inch so has a physical size. there are quite a few physical units that are dimension-less
J
jjs
Feb 26, 2005
"MOP" wrote in message
Of course it isn’t diemnsionless. It has a width and a height.

Technically it is dimensionless when you write it you say 10 pixels (for example) that does not have physical size, 1 pixel could be a mm or a mile but would still be a pixel.
where as when it’s DPI it dots/inch so has a physical size. there are quite a few physical units that are dimension-less

It’s rather like the US dollar; valueless until applied to a given market, and then it’s big or small.
Feb 26, 2005
On Sat, 26 Feb 2005 11:55:38 GMT, "MOP" wrote:

Technically it is dimensionless when you write it you say 10 pixels

Depends. One school of thought says 10 pixels is different than 10 bananas, so while, for instance, it’s valid to divide a quantity expressed in pixels by another expressed as pixels per inch to get a quantity expressed in inches, it doesn’t quite work the same with bananas.
Feb 26, 2005
"Andrew Morton" wrote:

However, text should be saved as text – an OCR program can translate an image-of-text into text.

Really? If it’s handwritten? Mathematical equations? Different language?

Yes. Handwriting is nearer to a drawing,

No, it’s _writing_. There was an age before print and computers and if I am not mistaken people still use it every now and then to record and relay information.

so I wouldn’t count that unless
only the text itself needs to be recorded.

The question is can an OCR program recognize handwriting (reliably)?

There are plenty of markup
languages for equations.

The question is can an OCR program recognize mathematical equations and symbols with ease?

Do you suggest nobody scibble those anymore but everybody carry notebooks with them and use markup language instead?

In what way might a different language be a
problem?

Does your OCR recognize Arabic prose?

The point being, sometimes it’s not feasible to OCR written text. That’s when you need to store or transmit such scanned documents as images, so the orginal poster has a very valid need.
J
jjs
Feb 26, 2005
"nobody" wrote in message

The question is can an OCR program recognize handwriting (reliably)?

No, and to head off those who say that the new tablet computers do a ‘good job’, note that their method relies upon information not available in a static bitmapped image, for example they sample characters as they are being made – direction of the drawing of the character and turns – to find statistical likelihood of the character being a,b,c etc.. And they still do a bad job. Mathematical symbols are harder yet for advanced mathematicians – if you knew the fights they have over accepted typography you would think them nutz.
H
Hecate
Feb 27, 2005
On Sat, 26 Feb 2005 10:54:03 +0000, Kennedy McEwen
wrote:

In article , Hecate
writes
On 24 Feb 2005 19:56:54 -0800, "toby"
wrote:

Hecate wrote:
On 23 Feb 2005 17:16:40 -0800, "toby"
wrote:

Some images don’t have meaningful physical dimensions (e.g. digital camera grabs); but many do (e.g. scans).
All images have physical dimensions. On a computer they’re expressed as pixels. On a print the resolution is expressed as dpi. The dpi is completely immaterial as far as an image on a computer is concerned.

A pixel count is dimensionless. The resolution value gives a pixel a physical scale. There’s really nothing to discuss here – this is all taken as read.
Of course it isn’t diemnsionless. It has a width and a height.
Oh don’t get us started on that again! Pixels are abstract objects which do not have any intrinsic dimensions *until* they are physically rendered. If they had a fixed width and height, how would you explain the same image, with the same pixels, being printed at different sizes – special relativity?

They are physically rendered on a computer screen – where they have a width and height expressed in pixels. I’m talking about images, I don’t know what you’re talking about.



Hecate – The Real One

veni, vidi, reliqui
H
Hecate
Feb 27, 2005
On Sat, 26 Feb 2005 11:55:38 GMT, "MOP" wrote:

Of course it isn’t diemnsionless. It has a width and a height.

Technically it is dimensionless when you write it you say 10 pixels (for example) that does not have physical size, 1 pixel could be a mm or a mile but would still be a pixel.
where as when it’s DPI it dots/inch so has a physical size. there are quite a few physical units that are dimension-less
Pixels yes. Images no. And unless I’m much mistaken, we’re talking about image files. Pixels may be dimensionless, but images have a width and height expressed in pixels when physically reproduced on a monitor.



Hecate – The Real One

veni, vidi, reliqui
D
dkcombs
Feb 27, 2005
In article ,
Kennedy McEwen wrote:
Rubbish, there are plenty of dimensionless units. Gradient of a slope is one example most people encounter at an early age. If the slope increases 1ft in every 10ft then it has a gradient of 0.1ft/ft – the units cancel out and you have a dimensionless gradient of 10%. It is pretty clear to everyone learning to walk that a 5% gradient is half as steep as a 10% one!

Interest rates are another example – for every $10 you invest your bank will give you $1. Interest rate is 0.1 dollars per dollar, or 10% – no dimensions. You would be pretty pissed off if your bank then turned

FALSE! (finally, something in this group that
I actually know something about!)

Dimension of an interest-rate is [1/T].

(Although after some thought it’s obvious, I first
saw that in a book
I own, "Dimensional Analysis for Economists")

Interest rate is: dollars per dollar — PER PERIOD OF TIME.

Hope this helps.

David
KM
Kennedy McEwen
Feb 27, 2005
In article , Hecate
writes
On Sat, 26 Feb 2005 10:54:03 +0000, Kennedy McEwen
wrote:

Oh don’t get us started on that again! Pixels are abstract objects which do not have any intrinsic dimensions *until* they are physically rendered. If they had a fixed width and height, how would you explain the same image, with the same pixels, being printed at different sizes – special relativity?

They are physically rendered on a computer screen – where they have a width and height expressed in pixels.

But that width and size of the image is not unique – on another screen exactly the same pixels will produce an image of another size, so the size is not an intrinsic parameter of the pixels. Just because a rendered image has a width and height does not mean that the pixels themselves have – it is the rendering process defines the width and height, not the pixels. The same pixels can produce an image the size of a postage stamp or half the surface of the planet – indeed, a significant portion of the visible universe if necessary!

Lets make it simple for you:
The image has n x m pixels. It is rendered at y "pixels per inch". The image height is therefore n/y pixels/(pixels/inch) = n/y inches. The image width is m/y pixels/(pixels/inch) = m/y inches.

ie. both width and height are determined from the calculation of the following units: pixels/(pixels/inch) = pixels/pixels * inches.

The dimensions of a pixel can be anything you like – oranges, elephants or chocolate cookies, because they completely cancel out in all calculations. Thus, invoking Occam’s razor demonstrates they need be nothing at all – completely *dimensionless*.

Now come up with a derivation of the dimensions you believe pixels to have, or just apologise to Toby for getting it wrong.

I’m talking about images, I
don’t know what you’re talking about.
So why did you dispute Toby’s statement that the pixel count is dimensionless – you may be talking about images, but you are talking to yourself! As Toby stated, the pixel count *is* dimensionless (which is the specific statement you disputed) simply because it is the total number of items which each have dimensionless units.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when replying)
M
MOP
Feb 27, 2005
"Hecate" wrote in message
On Sat, 26 Feb 2005 11:55:38 GMT, "MOP" wrote:
Of course it isn’t diemnsionless. It has a width and a height.

Technically it is dimensionless when you write it you say 10 pixels (for example) that does not have physical size, 1 pixel could be a mm or a mile but would still be a pixel.
where as when it’s DPI it dots/inch so has a physical size. there are quite a few physical units that are dimension-less
Pixels yes. Images no. And unless I’m much mistaken, we’re talking about image files. Pixels may be dimensionless, but images have a width and height expressed in pixels when physically reproduced on a monitor.

Then it’s pixels per inch, which is a different unit with the dimension of 1/inches 72 PPI being 1/72"
J
jjs
Feb 27, 2005
"MOP" wrote in message

Then it’s pixels per inch, which is a different unit with the dimension of 1/inches 72 PPI being 1/72"

What shape is that pixel, again? As an aside, I find it significant that these conversations are based upon geometric construction – and no irrational numbers.
M
MOP
Feb 27, 2005
"jjs" wrote in message
"MOP" wrote in message

Then it’s pixels per inch, which is a different unit with the dimension of 1/inches 72 PPI being 1/72"

What shape is that pixel, again? As an aside, I find it significant that these conversations are based upon geometric construction – and no irrational numbers.
And do I detect a Red Fish of the Herring family here?
J
jjs
Feb 27, 2005
"MOP" wrote in message
"jjs" wrote in message
"MOP" wrote in message

Then it’s pixels per inch, which is a different unit with the dimension of 1/inches 72 PPI being 1/72"

What shape is that pixel, again? As an aside, I find it significant that these conversations are based upon geometric construction – and no irrational numbers.
And do I detect a Red Fish of the Herring family here?

Do you? We do have nonsquare pixels, supported by CS even.


Mister Anamorphic
M
MOP
Feb 27, 2005
"jjs" wrote in message
"MOP" wrote in message
"jjs" wrote in message
"MOP" wrote in message

Then it’s pixels per inch, which is a different unit with the dimension of 1/inches 72 PPI being 1/72"

What shape is that pixel, again? As an aside, I find it significant that these conversations are based upon geometric construction – and no irrational numbers.
And do I detect a Red Fish of the Herring family here?

Do you? We do have nonsquare pixels, supported by CS even.

Mister Anamorphic
True! To be honest I can’t be bothered with this thread it is not going anywhere.
H
Hecate
Feb 28, 2005
On Sun, 27 Feb 2005 05:45:35 +0000, Kennedy McEwen
wrote:

Now come up with a derivation of the dimensions you believe pixels to have, or just apologise to Toby for getting it wrong.

As I said below I’m not talking about pixels per se. A pixel is just that. I’m talking about i9mages which do have dimensions.

I’m talking about images, I
don’t know what you’re talking about.
So why did you dispute Toby’s statement that the pixel count is dimensionless – you may be talking about images, but you are talking to yourself! As Toby stated, the pixel count *is* dimensionless (which is the specific statement you disputed) simply because it is the total number of items which each have dimensionless units.

Because I’m talking about images or am I mistaken in thinking a Photoshop group is about images?



Hecate – The Real One

veni, vidi, reliqui
KM
Kennedy McEwen
Feb 28, 2005
In article , Hecate
writes
On Sun, 27 Feb 2005 05:45:35 +0000, Kennedy McEwen
wrote:

I’m talking about images, I
don’t know what you’re talking about.
So why did you dispute Toby’s statement that the pixel count is dimensionless – you may be talking about images, but you are talking to yourself! As Toby stated, the pixel count *is* dimensionless (which is the specific statement you disputed) simply because it is the total number of items which each have dimensionless units.

Because I’m talking about images or am I mistaken in thinking a Photoshop group is about images?
You are certainly mistaken in thinking that you are just talking on a Photoshop group or that discussion of pixels and their counts is somehow off-topic on such a group.

There is nothing wrong with talking about images in any of the groups you are posting to, but there is something wrong when you dispute a perfectly valid statement and then claim to be talking about something else entirely. Most people would have the decency to say "sorry" about that rather than attempt to justify their error with misplaced semantics.

Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he’s pissed.
Python Philosophers (replace ‘nospam’ with ‘kennedym’ when replying)
T
Tacit
Feb 28, 2005
In Hecate wrote:

Pixels yes. Images no. And unless I’m much mistaken, we’re talking about image files. Pixels may be dimensionless, but images have a width and height expressed in pixels when physically reproduced on a monitor.

Correct. But because pixels are dimensionless, expressiong something in terms of pixels is also dimensionless.

Quick: I have a 223 by 617 pixel image. What are its dimensions? Answer: without knowing how many pixels per inch, you can’t tell. Might be an inch wide, might be six inches wide, might be half an inch wide, might be a mile wide.

"Ah," you say, "but on a monitor it has a dimension!" Does it? On my Viewsonic CRT and my Sony LCD, it’s sized differently; the size of a pixel on one monitor may be fixed, but it varies from one monitor to another. And once oyu know what monitor it’s on, and you know that monitor’s pixels per inch, NOW you know its dimension–because you know how many pixels per inch the monitor displays!

A pixel is dimensionless. Pixels per inch or pixels per centimeter, not dimensionless. Until you have a way to express not only the number of pixels but ALSO the number of pixels PER INCH, you are living in a dimensionless world.

Almost all image formats save not only pixels, but also information about the number of pixels per inch. This resolution information is irrelevant on a fixed-pixel output device like a computer monitor, but very relevanr on an output device like a printer. Any image format without a way to record resolution information, such as GIF, is an image format intended only for output on a monitor, not a printer.
H
Hecate
Mar 1, 2005
On Mon, 28 Feb 2005 16:12:27 GMT, Tacit wrote:

In Hecate wrote:

Pixels yes. Images no. And unless I’m much mistaken, we’re talking about image files. Pixels may be dimensionless, but images have a width and height expressed in pixels when physically reproduced on a monitor.

Correct. But because pixels are dimensionless, expressiong something in terms of pixels is also dimensionless.

Quick: I have a 223 by 617 pixel image. What are its dimensions? Answer: without knowing how many pixels per inch, you can’t tell. Might be an inch wide, might be six inches wide, might be half an inch wide, might be a mile wide.

"Ah," you say, "but on a monitor it has a dimension!" Does it? On my Viewsonic CRT and my Sony LCD, it’s sized differently; the size of a pixel on one monitor may be fixed, but it varies from one monitor to another. And once oyu know what monitor it’s on, and you know that monitor’s pixels per inch, NOW you know its dimension–because you know how many pixels per inch the monitor displays!

A pixel is dimensionless. Pixels per inch or pixels per centimeter, not dimensionless. Until you have a way to express not only the number of pixels but ALSO the number of pixels PER INCH, you are living in a dimensionless world.

Almost all image formats save not only pixels, but also information about the number of pixels per inch. This resolution information is irrelevant on a fixed-pixel output device like a computer monitor, but very relevanr on an output device like a printer. Any image format without a way to record resolution information, such as GIF, is an image format intended only for output on a monitor, not a printer.

OK, that makes sense. But surely, on a specific monitor a specific pixel will have a size? Just curious.



Hecate – The Real One

veni, vidi, reliqui
AM
Andrew Morton
Mar 1, 2005
The point being, sometimes it’s not feasible to OCR written text. That’s when you need to store or transmit such scanned documents as images, so the orginal poster has a very valid need.

The OP specified typed text, not handwritten text.

Andrew
T
tacitr
Mar 1, 2005
In article , Hecate wrote:

OK, that makes sense. But surely, on a specific monitor a specific pixel will have a size? Just curious.

A specific pixel on a specific monitor has a specific size, yes. This does not necessarily match the size of the pixel as it is recorded in the file, however.

A TIFF that is saved at 300 pixels per inch is made up of pixels, each of which is 1/300 of an inch across. When displayed on a monitor that happens to have pixels 1/96th of an inch across, the image displays larger than it will actually print.
H
Hecate
Mar 1, 2005
On Tue, 01 Mar 2005 18:02:56 GMT, (Tacit) wrote:

In article , Hecate wrote:

OK, that makes sense. But surely, on a specific monitor a specific pixel will have a size? Just curious.

A specific pixel on a specific monitor has a specific size, yes. This does not necessarily match the size of the pixel as it is recorded in the file, however.

I see.

A TIFF that is saved at 300 pixels per inch is made up of pixels, each of which is 1/300 of an inch across. When displayed on a monitor that happens to have pixels 1/96th of an inch across, the image displays larger than it will actually print.

Understand that, but I think the your answer to the first part above was why I was having some confusion i.e if 1 pixel has a dimension… Anyway, thanks for giving me a clear and logical answer.



Hecate – The Real One

veni, vidi, reliqui
N
nomail
Mar 2, 2005
Tacit wrote:

In article , Hecate wrote:

OK, that makes sense. But surely, on a specific monitor a specific pixel will have a size? Just curious.

A specific pixel on a specific monitor has a specific size, yes. This does not necessarily match the size of the pixel as it is recorded in the file, however.

A TIFF that is saved at 300 pixels per inch is made up of pixels, each of which is 1/300 of an inch across.

Actually, that is still not completely correct. A TIFF that is saved at 300 pixels per inch is made up of pixels, period. As long as it’s just a TIFF on a hard disk, those pixels do not have a dimension, they are just a bunch of bits. Only when you print that TIFF the pixels will get the dimension that is allocated to them by the ‘300 ppi’ info in the file. But even then that’s not always the case: Quite a few programs will overrule the ppi information if you choose some automatic size setting during printing, such as "Scale to fit media" in Photoshop.

Finally, to make it really correct: it’s not "1/300 of an inch across", it’s 1/300 inch wide and 1/300 inch long.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/

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