I read in the help (CS2) that Bridge can rotate the jpeg images without losing data. Can anyone confirm that this now is possible? Is it not possible from withing PS editor (would be strange)?
I believe in CS that if you specify a jpeg quality of 10 or 12 (maximum), that it doesn’t compress the file. So I’d guess the same would be true of CS2.
I believe in CS that if you specify a jpeg quality of 10 or 12 (maximum), that it doesn’t compress the file
Sorry Art, this is just not true. When you save a file as a jpeg, quality is lost. Period. Even if you don’t edit or alter the file in any way. Pixels are lost in the compression process even at maximum quality.
To prove it to yourselves try this little experiment as outlined in my recent post.:
I read in the help (CS2) that Bridge can rotate the jpeg images without losing data
I can’t be sure, but I imagine they are referring to the fact only the thumbnail is rotated. The actual file is untouched until you open it.
Having said that. I imagine it might be possible to rotate an image simply by rearranging the existing compressed pixels – in the same order, but from top to bottom (as it were) instead of side to side (over simplified analogy).
It is the opening of a jpeg (inventing the missing pixels) and saving it again (throwing away pixels for the purposes of compression) that causes image deterioration.
I’m sure someone more knowledgeable than I will chip in shortly with a more definitive reply.
The real answer is to ditch Jpeg in favour of a lossless format except for the purposes of internet and on-screen display.
Thx Chris and Art. Your (Chris) explanation is what I have learned too about jpeg and the difficulties with it. I think you may be right about the possibility of a rotation just being applicated to the thumbnail or the rearranging of pixels in the way you explain, or similar way. I will be ditching jpeg at the end of this year or beginning of next (hopefully) as I will be acquiring a Canon 30D (expecting such to be released by then) and then be sticking to RAW. But atm I still have 1500 old jpeg images in my album/DB and many need rotating.
Yes, saving them as TIFF is the best solution to jpeg images. I do use EXIFER atm though to edit metadata and rotate them. I will be batching my jobs too.
It is true that some graphic applications can rotate a JPG file in 90 degree increments without harming graphic data. XNView.com is another application that can do this. These operations do not really decompress and then re-compress the JPG file so no data is lost. This is not a modification of a thumbnail. The entire image is rotated.
Photoshop must open/decompress the JPG file before you can perform any transformation so there is always data loss when re-compressing the JPG file in Photoshop.
If you want to rotate a JPG file in 90 degree increments without data loss, use IrfanView or XNView or Adobe Bridge.
there was talk about lossless transformations (using free transform) at 90 degree rotations a while back. I wonder if that made it into cs2? anyone know?
brige does lossless jpg rotations you say? that’s cool.
Bridge justs save the need for rotation in metadata or the cache, and rotates the thumbnail. That way, it’s automatically rotated when opened in PSCS2, but the image is unchanged. I checked by rotating in Bridge and then opening in Irfanview; it opened unrotated.
I would love to see Chris Cox come into this thread. My understanding of jpg is that a loss occurs whenever a jpg is saved. Thus, opening a jpg and rotating the pixels may not degrade the image, but surely saving the file again as jpg will re-compress and a loss will occur.
This is the same as when one opens a jpg and saves it over and over again without changing it. We have been told that continued compression and degradation occurs with this.
Opening a Jpeg, decoding it into an RGB image, and then then resaving it as a Jpeg is definitely a lossy process, even at maximum quality. See this discussion <http://www.adobeforums.com/cgi-bin/webx?13@@.3bb9fc01/7 > for the results of my test. If, however, one simply manipulates the bytes to transform the coordinates of the stored data without decoding and recoding, it should be possible to save the file without additional loss.
Sorry to be a bit behind the rest of the human race but in the e mails regarding this subject i keep seeing the word "bridge" What is "bridge"
Always willing to learn Eddie
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I read in the help (CS2) that Bridge can rotate the jpeg images without losing data. Can anyone confirm that this now is possible? Is it not possible from withing PS editor (would be strange)?
My point would be that then such beast might exist,
I think chris said at one point waaaaay back that there is indeed such a mythical beast.
the context was when we were asking about the first save of camera data (the on camera save to the storage card) and why use a format that’s lossy from the get go. he stated there was a way to do a lossless save but didn’t elaborate…
My point would be that then such beast might exist,
I think chris said at one point waaaaay back that there is indeed such a mythical beast. the context was when we were asking about the first save of camera data (the on camera save to the storage card) and why use a format that’s lossy from the get go. he stated there was a way to do a lossless save but didn’t elaborate…
camera manufacturers offer it to save space on your storage card. if you don’t want your camera to use jpeg change the file format setting in the camera to tiff or raw.
Yes. Pixels are aligned on a vertical/horizontal plane. 90 degree turns (90, 180, 270, 360, etc.) should retain all the original data. However, rotating at other angles will force interpolation.
Peadge 🙂
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It is true that some graphic applications can rotate a JPG file in
OK people, There are at least several image programs outthere that do a LOSSLESS rotation of jpg images. They do not "convert" them or in any way "resave" them, thereby inducing the jpg compression loss. I don’t know the exact mechanism but it works. They keep all original data. ThumbsPlus in the Windows world and Graphic Converter on the mac side both have this VERY NICE feature. Maybe we can get a definitive answer from Adobe or something. It sure would be nice to have the workflow mostly if not wholly contained in PS.
It would be fairly easy to make a lossless jpg rotation the merely outputs the pixels vertically instead of horizontally. However, I am quite sure that this would not be part of the jpg standard (something Chris Cox is pretty adament about, I think) and would not actually rotate the jpg for other applications (something PS is designed to do).
I doubt Adobe would implement a non-standard format to solve a problem that so few people need.
It would be fairly easy to make a lossless jpg rotation the merely outputs the pixels vertically instead of horizontally. However, I am quite sure that this would not be part of the jpg standard (something Chris Cox is pretty adament about, I think) and would not actually rotate the jpg for other applications (something PS is designed to do).
This FAQ relates to a solved problem; some utilities that perform lossless rotation are listed here <http://sylvana.net/jpegcrop/losslessapps.html>. It does not violate any standard – the output image is just a standard JPEG – and it *does* physically rotate the image, unlike image browers that just tag it "rotate later".
