Some changes in libpng 1.6+ cause it issue warning or even not work correctly with the original HP/MS sRGB profile. You will notice this in stderr:
libpng warning: iCCP: known incorrect sRGB profile
The old profile uses a D50 whitepoint, where D65 is standard. This profile is not uncommon, being used by Adobe Photoshop, although it was not embedded into images by default.
The simplest solution is simply to remove the embedded profile from your image. This can cause a slight shift in color *IF* have have a properly calibrated system, monitor, and software.
This reverts commit 5d36e382c7.
It's been found to cause all kinds of terrain glitches on Windows and
Linux. Please do not try experimental image compression alternatives
without discussing and reviewing first.
Overall statistics (only for files with a smaller recompressed size):
Original size: 8179 KiB on 29 files
Optimized size: 7013 KiB
Total saving: 1165 KiB = 14% decrease
tod-schedule-* files each contains the individual ToD sky images for an entire schedule
tod-clouds-* files each contain cloud images that will be randomly overlaid on the sky image according to the expected lighting conditions of a given ToD
tod-template is a mask in the shape of the ToD window that will be used to crop any element it contains: ToD skies, clouds, terrain overlays, oversized unit sprites, …
Additional schedule images will be added later.
Overall statistics (only for files with a smaller recompressed size):
Original size: 16720 KiB on 404 files
Optimized size: 15237 KiB
Total saving: 1482 KiB = 8% decrease
