There is inconsistency among applications displaying an image with an invalid tRNS chunk containing values larger than the maximum pixel value for the image bit depth.

In the following table, the first three images should look alike, if the invalid tRNS chunk is being discarded by the viewing application. The fourth should have transparent replacing the black squares, and the fifth should have transparent replacing the white squares.


tRNS 0xff00

tRNS 0xffff

tRNS 0x0000

tRNS 0x00ff

The original image is the 0xff00 one, from wikipedia. The images all have bit_depth=8, so the maximum valid tRNS value is 0xff.

Page by Glenn Randers-Pehrson, April 2008.