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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.