Add nix flake check to test for transparency
Running pngcheck -v bitwig.png
prints the output
File: bitwig.png (41867 bytes)
chunk IHDR at offset 0x0000c, length 13
768 x 768 image, 32-bit RGB+alpha, non-interlaced
chunk bKGD at offset 0x00025, length 6
red = 0x00ff, green = 0x00ff, blue = 0x00ff
chunk IDAT at offset 0x00037, length 8192
zlib: deflated, 32K window, default compression
chunk IDAT at offset 0x02043, length 8192
chunk IDAT at offset 0x0404f, length 8192
chunk IDAT at offset 0x0605b, length 8192
chunk IDAT at offset 0x08067, length 8192
chunk IDAT at offset 0x0a073, length 772
chunk IEND at offset 0x0a383, length 0
We can parse this in haskell and add a flake check that makes sure all pngs have the correct alpha channel data.