The data at offset 0x1E should be the compression method rather than the channel number https://github.com/folksable/blurhash_ffi/blob/c24986763bb3abb801ec7491448924c86a9b8f9d/lib/blurhash.dart#L555 https://en.wikipedia.org/wiki/BMP_file_format#DIB_header_(bitmap_information_header)
The data at offset 0x1E should be the compression method rather than the channel number
blurhash_ffi/lib/blurhash.dart
Line 555 in c249867
https://en.wikipedia.org/wiki/BMP_file_format#DIB_header_(bitmap_information_header)