GNOME Bugzilla – Bug 101844
Saving an original JPEG creates a smaller image
Last modified: 2009-08-15 18:40:50 UTC
I had some pictures (of Moths) of about 1.500 kB. I changed them a little and than saved them. The sizes were decreased by about 1.000 kB or more. I tried this again on smaller pics and these were also considerably increased (from 66 kB to 17, 87 kB to 24). This only happened the first time I saved them after a 'save as' e.g. to create a file comment. Later saving kept the image-size as it was before, but nevertheless about half the size of the original. I think that I can work around this problem by using 'save as' any time that I want to save the file but 1. that is not very convenient and 2. when I use 'save' by mistake, my file is shrunk automatically.
This is because the JPEG plug-in currently can't read the save quality at load time for jpeg images. The workaround is to save at a very high quality when you're saving the image the first time. This is related to another (fixed) bug which concerns plug-ins setting default values - in cases where eth save values cannot be read from the image, they shouldn't be guessed. In brief, you are saving your jpegs at a lower quality than the original, this is why they are smalelr. To have your saved images about the same size, you should increase the save quality to 90 or 95%. Given that the bug report mentions that this happens during a "Save As", and not just during a "Save", I think we can close this bug as NOTABUG. Cheers, Dave.
Received a mail from the original submitter informing me that I misunderstood his report, and that he didn't know how to attach the comment on bugzilla. I will attach his mail when I can, in the meantilme I'm changing trhe status to reopened. Dave.
Sorry - technical difficulties meant that I didn't have the mail until now - attaching it here. Hello Dave, Thanks for your prompt reply on my problem, on which I however still have a problem. I do not know how to change my comment, therefor I try your e-mail in hope that you can tell me the proper way. My problem/comment: This only happened the first time I saved them after a 'save as' e.g. to create a file comment. Your comment: "Given that the bug report mentions that this happens during a "Save As", and not just during a "Save", I think we can close this bug as NOTABUG". No, I do not agree. It is just the contraire, I think I was not clear enough so you misunderstood. I first used 'save as' to add a comment, during this save as I increased the quality to about 95% (and pressed the button 'optimize'). Then, after I changed something, and I said -> right-click, ->file, ->save then my picture is shrunk. That is why I wrote: "I think that I can work around this problem by using 'save as' any time that I want to save the file but 1. that is not very convenient and 2. when I use 'save' by mistake, my file is shrunk automatically." because then I can adjust the quality of the picture and not by just using 'save'! I hope that I made clear what I mean, because for me, as a Dutchman, it is not easy to explain such a problem of a bit theoretically type in the technically right way. Kind regards, Sicco
For what it's worth, I can't reproduce this. the jpeg-save-vals parasite gets correctly created and attached to the image at a Save As, and during saves afterwards, the resulting images are more or less the same size as the size after the Save As. Cheers, Dave.
I think this is a duplicate of bug #75398.
I thought so at first too. However, the original author says that this occurs after a "Save as" where he sets quality settings to his preferred level. During a Save as in the jpeg plug-in the jpeg-save-vals parasite is attached to the image, and all future saves of that image should use those correctly. The original author reports that those values aren't respected when he saves. As I read it, it's a different issue. But I'll repeat, it's not an issue I've been able to resolve. Perhaps Sicco could add some further information? Cheers, Dave.
After reading bug #75398 carefully, I must admit that it seems to have a lot in common with my problem, although I do not completely understand the statements about plug-ins and parasites (my knowledge of this, for me rather technicall English is just not enough). I try to give a better description of my problem in order to give you the opportunity to decide if this is a duplicate or not. 1. I scan a foto or diapositive, at a choosen quality. 2. I work on that foto and use 'Save as' in order to add a comment. during this 'Save as' I adjust the quality from 75% to a value between 90 and 100%. The result is a file that has about the same size or is even (much) bigger than the original. 3. After reopening this foto and some changing I pressed 'Save' or 'ctr-s', the result is a considerable smaller file with less quality, which I do not want. 4. After reopening this smaller foto adjusting it and then saving it again with 'Save', the quality is about the same as before this action. Hope this helps to decide whether this is a duplicate or not, my suggestion however is that, when I read it over, it is. Sicco
The GIMP cannot determine the settings you used to save a JPEG when you open it. This is a problem with the JPEG file format since the information is simply not stored in the image file. Thus, when you are opening a JPEG file and later save it, you need to determine the quality settings. Due to bug #75398, the JPEG plug-in used to use default settings instead of asking the user. Your report is thus a duplicate of #75398. The main problem here is however that your work-flow is flawed. You should never save an image using the lossy JPEG format unless you are distributing a final version of it. Even then you should keep a copy in a lossless format. Otherwise you will loose quality every time you edit the image and fter a couple of open-save iterations the artefacts introduced by the JPEG compression algorithm become visible. *** This bug has been marked as a duplicate of 75398 ***
The fix is part of the stable release 1.2.4. Closing this bug.