Types from the PNG spec: 0 - greyscale 2 - truecolor 3 - indexed color 4 - grey with alpha 6 - true with alpha
1, 5, and 7 are invalid.
There's a kind of bitmask going on here: If type&1, it has a palette. If type&2, it is in color. If type&4, it has an alpha channel in the datastream.
See Implementation
Types from the PNG spec: 0 - greyscale 2 - truecolor 3 - indexed color 4 - grey with alpha 6 - true with alpha
1, 5, and 7 are invalid.
There's a kind of bitmask going on here: If type&1, it has a palette. If type&2, it is in color. If type&4, it has an alpha channel in the datastream.