Tiff: IOError: cannot identify 16-bit TIF file

[lackas]

When trying to open a 16-bit DirectClass TIF file, Pillow fails with IOError: cannot identify image file 'rose16.tiff' error message.

Using ImageMagick's standard rose example an 8- vs 16-bit depth options one image loads, while the other fails. This is on a standard CentOS 6 with libtiff 3.9.4 (which is also used by IM, so it is not an issue of libtiff)

from PIL import Image

# # Use ImageMagick's convert tool to create example images with 8- and 16-bit color depth:
# convert rose: -depth 8  rose8.tiff
# convert rose: -depth 16 rose16.tiff

im8  = Image.open("rose8.tiff")
im16 = Image.open("rose16.tiff")

# IOError: cannot identify image file 'rose16.tiff'

[wiredfool]

Can you post the image that fails?

[lackas]

Sure, here are the working and failing tif image, both created by ImageMagick:
rose.zip

$ identify rose16.tiff 
rose16.tiff TIFF 70x46 70x46+0+0 16-bit sRGB 19.6KB 0.000u 0:00.000

$ identify rose8.tiff 
rose8.tiff TIFF 70x46 70x46+0+0 8-bit sRGB 9.96KB 0.000u 0:00.000

[wiredfool]

The 16 bit image is an unsupported format. Pillow doesn't support multiband images with individual channels > 8 bit, and that is a 3 x 16 bit image.

(that's despite imagemagick calling it a Depth: 16/8-bit image)

There's an open issue for adding support: #1888