Indexed .PNGs don't seem to handle alpha channel correctly

[gerald-lindsly]

Alpha channel is not working right on this indexed image

Platform

• Architecture: x86-64
• OS: Android emulator
• API 34

[gerald-lindsly]

My bad... Setting the SPNG_DECODE_TRNS flag in the spng_decode_image() function did the trick. However, I think this should be the default,