tree ae7bac874cdac199adbddcf9a94971e2c963636a
parent 63a496c80343b67e1d5e84f984cc275a2986ee43
author Vignesh Venkatasubramanian <vigneshv@google.com> 1684256168 -0700
committer Vignesh Venkatasubramanian <vigneshvg@users.noreply.github.com> 1684341359 -0700

Allow alpha to be specified as an auxl of color tiles

Allows images of the following form to be decoded as images with
alpha channel (since the spec does not disallow these):

[primary item grid]
   ^       ^
   |dimg   |dimg
   |       |
[color] [color]
   ^       ^
   |auxl   |auxl
   |       |
[alpha] [alpha]

Fixes Issue #1203.

I have tested this commit with the image attached in issue #1203
and it decodes as intended with the alpha plane.