PSP vs. Gimp file sizes
kyoto kid
Posts: 41,057
...I recently noticed a difference in .jpg file sizes between saving in PSP and Gimp for the same image.
Example, last night I was working on a piece for submitting to a gallery that had a tight file size (not image size) requirement. The image was 1,500 x 1,111 and when saved to a .jpg in Gimp the flesize was just over 1,600k. I then loaded the same original .tif file into PSP and after saving to a .jpg the file size was slightly over 1,200k. In both instances the file was saved with 0% compression at 96 dpi.
Now I would think that a file format would retain the same properties under the same file save settings no matter which application was used. To me this says there is still a level of compression occurring with PSP even though I set the compression to 0% in the advanced settings wizard.
Any insight on this?
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As far as I know jpg is always lossy, even at 100% quality (which is what the slider should be, not a measure of compression - most image formats have compression, the difference is between lossy methods like JPEG and lossless methods like PNG or TIFF).
...however .tif and .png tend to have larger file sizes than .jpg and most galleries (including here) will not accept .tif format.
I just don't understand why saving the same image in two different programmes results in different file sizes. Does that mean Gimp is superior to PSP when it comes to final image quality?
Photoshop jpgs are always larger that PSP ones as well.
No, it just reflects slightly different implementations of the compression algorithm. Lossy formats will save smaller as they are willing to approximate the image to get it to fit nicely with the compression, the quality setting determines how much compromise is allowed. Of course one or the other may give a visually more acceptable result for a given file-size or quality setting, but it won't necessarily be the same one at every point or for every image - all you can do is try them and see.
...hmm. Well I always render to a .tif to perform all my postwork as I understand .jpg tends to lose more quality each time you save/open the file to perform a new process. Once I am satisfied the piece is complete, I then reopen it and save to .jpg format to upload.
The odd thing with PSP is when I re-save as a .tif in Gimp and then open it up in PSP, an alpha channel layer is superimposed over the image for some reason.
Well it comes down to which jpg code was used in the program. The difference comes down to that in each Program. There is more than one default jpg compression code that can be included in any save out routine. As long as it produces a valid jpg file that is all that really maters to the coder. The default compression can vary a great deal from code to code.
...reminds me of the old BASIC language of the 1970s - no standardisation whatsoever. Crappy setup for something that should be an industry standard.
Except that in this case the jpgs should "run" OK, it's just a question of how they were generated. Tiff is the one that can be chancy going from one application to another.
Well, it goes from Zbrush and 3dCoat to GIMP and back okay. Can't speak to PSP or Photoshop. ;)
I always save my renders as .png files. Once I have saved a render as .tiff file, tried to open it in Photoshop, but could not. Photoshop said the file was corrupted. So I always use .png, never had any problems with them.