Chunk types with these prefixes will never be assigned in the public specification. Also note that others may use the same proprietary prefixes, so it would be advantageous to keep additional identifying information at the beginning of the chunk. All PBF implementations must accept the following chunk types in order to be considered PBF-compliant. All implementations must understand and successfully render the critical chunks below. 1 byte Width and height are 4-byte integers.
Bit depth is a single-byte integer.
A value of 16 is also valid, but support for this is optional. Software that does not support a bit depth of 16 should acknowledge this if possible rather than indicating that the image is at fault. Bit depths of 16 should in any case never appear with color type 1. Color type is a single-byte integer. Color type determines the interpretation of the image data.