can't save replaced color

[yky]

I replaced all the black colors in a jpg image to red, saved the file, opened the file and found that it's the same image before replacing colors. I did the same replacement again but this time saved it to a different file. Again, no change. The replaced colors were not there. Somehow during saving, the image reverted back to the original. How should I save the color-replaced image?

This is version 4.54 32-bit on Windows 10 19041.928.

[Bhikkhu Pesala]

I doubt if 4.54 is any different, but you should upgrade to the latest version: 4.57

I had no problem replacing the dark grey in the Avatar with black, then replacing the black with red.

[yky]

I doubt if 4.54 is any different, but you should upgrade to the latest version: 4.57

I had no problem replacing the dark grey in the Avatar with black, then replacing the black with red.

Thanks for the reply. I upgraded to 4.57 and tried it again. The same thing happened. Changes are not saved.

Yes. I can do what you did. When I changed the color of a large area and saved the file, the change was saved. The following picture is what I have been working on. I can change the red color, about 99.8% of the area, to black, save the file, and the change is saved. If you enlarge the picture, you'll see that on the border, some pixels have a darker color. When I replaced those darker colors to red, the change couldn't be saved. The only way I have found so far to save the change is to save the file as .png, not .jpg. If I keep the .jpg format, no change is saved.

[Bhikkhu Pesala]

The image has artefacts, like all JPG images. You will have to play with the tolerance when swapping colours to change the nearly red pixels.

[yky]

Do you mean I cannot rely on what I see on screen? On screen, after change, the picture was uniformly red. The darker pixels were gone. However, when I save it, the darker pixels reappeared. If I cannot rely on what I see on screen, how do I tell whether the color of dark pixels have changed?

By the way, the tolerance was initially set to 128. Later, after finding the change was not saved, I changed it to 12. It didn't make a difference. The change was not saved. This was done before I posted the question.

[Bhikkhu Pesala]

When you save as JPG artefacts are added. Images like yours should be saved as PNG. They will be lossless and smaller.