Reported Image is altered by fitting it to window with try to improve gamma option enabled

[mechaskrom]

-Enable the "Try to improve gamma for Resample" option in the "Resize/Resample image" dialog.
-Use some option in "View->Display options (window mode)" that will fit image to window e.g. "Fit images to window".
-Open and save an image and it will get altered (some colors change slightly) without actually resizing its dimensions.

Happens in 4.42 32-bit and 64-bit version. See this thread for more info: https://irfanview-forum.de/showthread.php?t=10837

[Mij]

This is what you said in the thread you referenced, so I suppose you still believe it to be true.

-Use some option in "View->Display options (window mode)" that will resize image on open e.g. "Fit only big images to window".

It is not true that opening an image with View set to "Fit only big images to window" resizes the actual image that was loaded.
It just resizes what you see on the screen so that it fits into the window. It does not use the "Resize/Resample image" dialog settings to do that.

So if you then save it (without opening the Resize/Resample dialog and applying it to this image) it will still be the original size. That is the correct result and if you do see color changes it is some other feature setting that is doing it. Nothing to do with the Resize/Resample dialog because you have not applied it.

Personally I do not know why that gamma setting is in the Resize/Resample dialog. If it does improve the gamma it has never been enough for me to see any difference. If I need to adjust the gamma I use the Color corrections dialog.

[Mij]

-Enable the "Try to improve gamma for Resample" option in the "Resize/Resample image" dialog.
-Use some option in "View->Display options (window mode)" that will fit image to window e.g. "Fit images to window".
-Open and save an image and it will get altered (some colors change slightly) without actually resizing its dimensions.

Happens in 4.42 32-bit and 64-bit version. See this thread for more info: https://irfanview-forum.de/showthread.php?t=10837

In the thread you referenced you also said

-Enable the "Try to improve gamma for Resample" option in the "Resize/Resample image" dialog.
-Use some option in "View->Display options (window mode)" that will resize image on open e.g. "Fit only big images to window".

So I get the impression that you think setting the "View >Display options (Window mode)" so that the image must be resized to fit it into a window will cause the settings in the "Resize/Resample image" dialog to be applied to it and will also have been applied to what you subsequently save. Neither is true.

Unless you open the "Resize/Resample image" dialog and apply it to the current image by pressing "OK" in that dialog, you will not have applied any changes to what you save. It will still be the same size. That is the correct operation.

If you do see any color changes in what you have saved it will have been applied by some other feature. Personally I have never been able to see any visible effect of setting that Gamma feature in the Resize/Resample dialog and do not know why it is still there. If I want to adjust the gamma I use the Color corrections dialog.

[mechaskrom]

It just resizes what you see on the screen so that it fits into the window. It does not use the "Resize/Resample image" dialog settings to do that.

I agree!, which is why I'm making this bug report. Try to improve gamma is applied when fitting an image when it just should be applied when actually resizing an image with the Resize/Resample dialog.

Try this if you don't believe me:
-Create in your favorite image editor an image that is 32x32 pixels big and fill it with color 16,16,16 RGB (black, all components set to 16). I've attached one for your convenience.
-Open Irfanview and enable "Try to improve gamma for Resample" and "Fit images to window". Close Irfanview.
-Open the 32x32 image and the color is changed to 15,15,15 RGB when fitted to window. Check with the "hold-mouse-down-tool" for example or save the file and check in your editor.

A table maybe is clearer:

Try to improve gamma for Resample	Fit			RGB
disabled				not anything		16,16,16
enabled					not anything		16,16,16
disabled				to window		16,16,16
enabled					to window		15,15,15	<-Altered!

I've tried this on two different computers with the same result.