1

I used GIMP to draw and after couple of weeks I noticed that image isn't as sharp as it was before. It seems GIMP can't save a file without quality loss: the more times you save file, the less and less quality you get. Is it possible to change that, may be some settings? I'm not talking about exporting, but exactly about saving.

  • This normally doesn't happen when saving. Can you add to your question a PNG of two generations of the same image, and describe what you have done in between? – xenoid Jan 16 at 8:01
  • @xenoid I don't have old version of the image, I saved it in .xcf format. I uploaded JPG image with pencil sketch to make it in color. I used paintbrush tool and smudge tool. After several days I noticed that image became more blur (including areas that finished several days ago). I didn't apply any filters to the image. – R S Jan 16 at 8:21
  • 1
    If you are opening a jpg and then saving as a jpg, there's going to be quality loss with every save. – Scott Jan 16 at 8:38
  • Sp hard to tell without hard data. Retry on another image and keep the initial version, then let us compare both initial/final. – xenoid Jan 16 at 8:40
2

If you are talking about editing and saving a JPEG repeatedly, then what you have descirbed is normal behaviour.

JPEG is a lossy format. So, every time you edit and save a jpeg, it will degrade. The more you do that, the worse it will get.

This has nothing to do with GIMP. It's because of the JPEG format itself, and how it uses compression. This will happen no matter what image editor you use, including Adobe Photoshop.

The solution is to save in a lossless format, such as GIMP's native XCF format, or PNG, or TIFF. You should use GIMP's native format if you want to preserve layers and text layers for further editing.

1

If you do global color changes (Curves, Levels, Brightness/Contrast, Hue/Saturation) then you lose colors on every change (5% to 10% of the colors, for some heavy-handed changes). This typically leads to banding and general image quality loss. You check this in the Gimp histogram dialog (`Windows>Dockable dialogs>Histogram) which will assume a "haircomb" look:

Normal histogram:

enter image description here

Haircomb histogram after adding contrast (all the "white lines" are missing colors)

enter image description here

This has nothing to do with Gimp itself and will happen in any image editor on 8-bits/channel images (JPEG/PNG/GIF...). You should try to do these change together in one shot (often using Curves).

Another if you use Gimp 2.10, you can also switch the image to high precision (Image>Precision) and use dithering during conversion (here are setting to make that automatic when you load images, if necessary). Color loss will also happen, but will be much less visible.

  • I was drawing on opened JPG image of sketch. So I should open JPG and switch to 32 bits and then paint on it, right ? – R S Jan 16 at 8:27
  • If you are just painting this shouldn't change anything if you save (of course if your export to/reload from JPG every time then you could have generation loss, but his isn't what you are doing, right)? – xenoid Jan 16 at 8:38
  • that's correct. – R S Jan 16 at 10:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.