image-rs
TIFF files with unassociated extra samples are unsupported.
TIFF files with 2 samples per pixel (Luminance + Alpha) are unsupported by this library. Such TIFF files are the default output of imagemagick if the input is grayscale.
Attached is an example. example_tiff.zip
Do you know where specifically the error is coming from? GrayA is listed as a supported color type and I believe that most of the code doesn't care how many samples per pixel there are.
It seems, imagemagick does not encode it as a truly alpha component but as a mask:
$ tiffinfo *
TIFF Directory at offset 0x80008 (524296)
Image Width: 512 Image Length: 512
Resolution: 1, 1 (unitless)
Bits/Sample: 8
Compression Scheme: None
Photometric Interpretation: min-is-black
Extra Samples: 1<unassoc-alpha>
FillOrder: msb-to-lsb
Orientation: row 0 top, col 0 lhs
Samples/Pixel: 2
Rows/Strip: 512
Planar Configuration: single image plane
Page Number: 0-1
White Point: 0.3127-0.329
PrimaryChromaticities: 0.640000,0.330000,0.300000,0.600000,0.150000,0.060000
This is probably intended in this case (pistol_scope_mask.tif) but quite possibly the reason that it's not commonly encountered or reported as such.
The library doesn't guess the meaning of extra channels and unassociated extra samples aren't supported.
