Based on the PNGsuite.
The following images show the use of transparency channels. Again all three rows should look identical,
the first row being the reference point. If the rows do not look identical your software does not
correctly handle transparency. Each row contains the same set of 4 images both on a white and on a gray background.
For each of the images the background should shine through partially.
The second row of images contain a bKGD chunk with (from left to right) the color yellow, white, gray & black.
The chunk should however not be rendered by the software, as the MNG contains a mandatory BACK chunk!
The following images were used (left to right):
bgyn6a16 - 3x16 bits rgb color, alpha, yellow background chunk
bgwn6a08 - 3x8 bits rgb color, alpha, white background chunk
bggn4a16 - 16 bit grayscale, alpha, gray background chunk
bgbn4a08 - 8 bit grayscale, alpha, black background chunk
bgan6a16 - 3x16 bits rgb color, alpha, no background chunk
bgan6a08 - 3x8 bits rgb color, alpha, no background chunk
bgai4a16 - 16 bit grayscale, alpha, no background chunk, interlaced
bgai4a08 - 8 bit grayscale, alpha, no background chunk, interlaced