TIFF File size & compression

SC
Posted By
Sean_Cahalan
Oct 6, 2003
Views
649
Replies
13
Status
Closed
I use Photoshop 6.0.1 to edit scanned line and text images in tif format. The originals are +/- 8.5"x14" with a file size of <100k. If I open one in Photoshop and edit it, rotate for example, and resave it the file size jumps to +/-4 meg. I take this to be due to the type of compression but I can’t figure out how to choose or change that in Photoshop. In Paint Shop Pro there are compression options but I can’t find the equivilent here.
BTW, I realize Photoshop is way more program than I need for what I’m doing, anyone have any suggestions for a simpler alternative? I’m not doing graphic arts, just cleaning up scans.
Thanks

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BLUDVLZ
Oct 6, 2003
Sean,

What color mode are you scanning your image in (bitmap, grayscale, RGB, etc.) and at what resolution?

What I am thinking at the moment, is that you are scanning in your image in lineart mode, but (in order to rotate) you have to change them to grayscale, which changes the file from its native 1-bit depth. As a result, you get a larger file.

So if this is the case, convert your image to grayscale, make your necesary adjustments then convert back to the bitmap color space and see if you don’t get your small file size back.

Let me know if this doesn’t work.
SC
Sean_Cahalan
Oct 6, 2003
I thought you might be on to something because I always have to change modes to grayscale to rotate. Then I opened an image, made no edits and saved it as a new file. Same thing happened, orig size 72k, new size 4166k. I opened it up again and checked the mode and it is bmp.
SC
Sean_Cahalan
Oct 6, 2003
Sorry, forgot the rest of your question. I am scanning with a Kyocera-Mita 4850W wide format scanner that has virtually no user input, all I can adjust is contrast. It judges original size, format, etc. I am waiting to here back from KM about what compression they use.
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BLUDVLZ
Oct 6, 2003
Okay Sean, here’s what I did. See if it tracks with what you’re doing…

1) Created a new file (8½x14, 300ppi, bitmap color space). File size came in at 1.28 MB.

2) Drew a scribbly black line on the white background.

3) Converted to Grayscale with a size ratio of 1. File size came in at 10.2 MB.

4) Double-clicked on the background layer to make the image "transformable."

5) Went to Edit>Transform>Rotate and rotated the image.

6) Converted the image back to the bitmap color space with 300ppi listed as the output resolution and 50% Threshold as the Method. File size came in at 1.28 MB.

So based on this, you should have the same file size as before. I would suggest checking all your conversion settings as you convert from bitmap to grayscale to bitmap. I think the most likely setting that is causing the increased file size is the Output Resolution when converting back to bitmap. My bet is that it’s defaulting to 1200ppi, thereby causing the increased file size.

Hope this is the case. Let me know.
SC
Sean_Cahalan
Oct 6, 2003
The images I work with are created by the scanner, I forgot to mention @400 dpi, so all the attributes the machine uses for the file.
In the test case I did this morning I made no changes to the file, didn’t rotate, change to grayscale or anything, just saved the file with a new name.
As for dbl clicking the background layer, I don’t know photoshop that well and don’t do that. I just have the image open and choose rotate from the edit menu. All I do is change modes to be able to rotate arbitrarily. I haven’t been changing back to bmp when I finish.
With the test case though I didn;t make any changes and the file size changed 5400%. I will try converting an image back to bmp and see if it helps.
Thanks
SC
Sean_Cahalan
Oct 6, 2003
I opened a 73k file, saved it w/new name with no edits, size = 4814k. Converted to grayscale w/no edits size = 38475k. Converted back to bmp w/original res. of 400 dpi, size = 4814.
Opened that file in Paint Shop Pro and saved as new name using LZW comp. and rgb color channels, size = 308k.
I haven’t made any edits at all, just saved the file.
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BLUDVLZ
Oct 6, 2003
Sean,

Would you mind sending me a file (fresh of your scanner)? Let me see if I can reproduce your problem on my machine.

Just click on my name to get my email address.
JS
John_Slate
Oct 6, 2003
File size issues aside …when it comes to the text, why not use OCR software and spend a little time properly formatting the text? Of course if you’re not lucky enough to have OCR that recognizes fonts (is there such a beast?) you kind of need to know type faces.
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Sean_Cahalan
Oct 6, 2003
I’m not extracting text, just archiving survey plats.
JS
John_Slate
Oct 7, 2003
You can save a bilevel bitmap tiff with LZW compression and it makes a big difference. How are you saving your’s Sean? Is LZW checked in the tiff options during the save?

I made a 8.5×14 400ppi bitmap mode file with a bunch of lines and some text, and it weighed in at 2.27MB as a normal tiff but went down to 204KB when saved with LZW compression.

I would wager that the raw scans include some heavy duty compression, perhaps proprietary as you suggest. I would be curious to hear what the scanner manufacturers say.
SC
Steve_Coates
Oct 7, 2003
Sean:

You didn’t give specs on your scanner. At a guess, your files are probably being saved as Group 4 tiff, which is a format not supported by Photoshop. What is your end goal? Have you considered using Acrobat or must the files remain as tiff?

Steve
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Chris_Cox
Oct 7, 2003
Steve – Photoshop does read Group 4 TIFF, but cannot write it.
SC
Steve_Coates
Oct 7, 2003
ya, iknow, sorry i wasn’t more precise, but …

Steve

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