According to its specification, the PNG format has several "types": 0 : grayscale without alpha channel (1,2,4,8,16) 2 : true color without alpha channel (8,16) 3 : indexed color (1,2,4,8) 4 : grayscale with alpha channel (8,16) 6 : true color with alpha channel (8,16) (Please note that ALL types support transparency, even without an alpha channel. With #3, transparency is defined as part of the RGBA palette; with #0 & #2, transparency is GIF-style: Assign one RGB color as 100% transparent pixel.) Which types are supported by the game and/or Content Patcher? EDIT: The reason I'm asking this is that I want to optimize the PNG files of the hundred+ mods I use. With OptimPNG, if I do not restrict it, sometimes it converts the PNG file from Type 6 to Type 3 or Type 2. The end result is indeed much smaller than the original PNG, but I'm concerned that the changed Type will cause issues with the game and/or graphic patcher mods such as CP.