Hi again.
I had hopes that if I waited on the bench for a few rounds of updates, the problem might get resolved in the meantime by some of your fine coders, but unfortunately I was not so lucky. At least not yet. I am now at WP v. 4.5.2 and Gmedia Gallery 1.8.25 and the problem persists.
Uploading an 1200x1800px image results in the downsampled 300x450px thumbnail image having desaturated colors.
I am not sure I understand the reasoning behind your answer #6920. If Gmedia is using wordpress functions that have changed, shouldn’t the gallery be updated to reflect these changes so that it would still function correctly? Is your answer really that your users should stay put in the old days when the world was still compatible with your plugin? And even if so, rolling back wordpress is not really an option is it? Or even wise from a security standpoint?
Anyway, I found another problem with the plugin. I tried to bump the saturation of the thumbnail up a bit with your built in editing functions, to see if I could get it to look more like the colors of the full size target image in spite of the desaturation. Using any of your built in editing functions will, however, result in a completely black frame.
If there really is a problem with WordPress image functions maybe your coders would be better suited than I to discuss the problem with the people who maintain the wordpress codebase?
Rgds