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Maniphest T86570

75% jpg compression on reload
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Description

System Information
Operating system: Linux-5.4.73-1-lts-x86_64-with-glibc2.32 64 Bits
Graphics card: GeForce RTX 2070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 455.38

Blender Version
Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-03-13 22:49, hash: rB1f8d27a191c9
Worked: (newest version of Blender that worked as expected)

Short description of error
Blender stores 75% compression after Gimp or Krita 98% compresssion jpg saving.

Exact steps for others to reproduce the error

copression_jpg_file.blend684 KBDownload

Save the image on Image Editor to jpg 98% compression with blender

Open this image with Krita or Gimp and save with 98% jpg compression

Come back to blender and reload the image.
And save as a new time on blender and the jpg compression file is 75% !!
But Gimp and Krita memorise 98%

It is hard to explain well this bug but it is really bad for me because I loose images with 75% compression !!

Event Timeline

Damien Monteillard (lastrodamo) created this task.Mar 14 2021, 10:03 PM
Robert Guetzkow (rjg) changed the task status from Needs Triage to Needs Information from User.EditedMar 14 2021, 11:30 PM
Robert Guetzkow (rjg) added a subscriber: Robert Guetzkow (rjg).

The compression ratio or quality setting of the programs are independent. If you save the image with a certain quality setting in Gimp and then open it in another program, that program will decompress the image. When you try to save it as jpeg again, it will display the default quality settings / compression options of that program, no matter what you had chosen in your initial save in another software. If the defaults are different, the settings will be different.

In case you are not aware jpegs compression is lossy, meaning that the compression algorithm discards information. Thus saving the image again and again will lead to a degraded image quality. I would recommend you use an image format that provides lossless compression.

Unless I'm misunderstanding your description this is not a bug.

Damien Monteillard (lastrodamo) added a comment.EditedMar 14 2021, 11:55 PM

Thank you for your answer.
So default compression jpg is 75%... I think is really bad default. 95% will be better to haven't bad compression artifact.

I would prefer png compression but :
If you have 200 textures (500ko) png files (1024x1024px) 500x200=100Mo of files. With jpg this is around 40Mo.
With png there is a huge RAM memory consuming. And I wouldn't want. And 95% jpg is a solution for this.

Have you a better image format with a lowest size of file ?

Campbell Barton (campbellbarton) closed this task as Archived.EditedMar 15 2021, 12:09 AM
Campbell Barton (campbellbarton) added a subscriber: Campbell Barton (campbellbarton).

Checking on Exif meta-data, it seems JPEG doesn't have a standard way to store the compression level.
Blender uses it's own non-standard meta-data that other applications will not recognize.

Closing as this isn't a bug.