YCbCr mode TIFF saving not functional

[kmilos]

This is w/ Pillow 8.3.1.

1. Uncompressed saving (i.e. not using libtiff_encode) doesn't set tag 530 to (1,1), and mandatory tag 532:

import PIL.Image
image = PIL.Image.new('YCbCr', (1760, 1046))
image.save('test_ycbcr_nocomp.tif')

Resulting file is invalid - compare to tags in tiff_strip_ycbcr_jpeg_1x1_sampling.tif

2. When using compression and/or libtiff_encode, even if added somehow, tag 530 doesn't get stored correctly and encoding fails:

import PIL.Image
image = PIL.Image.new('YCbCr', (1760, 1046))
image.save('test_ycbcr_libtiff.tif', compression='jpeg')

See also #5588 (comment)

[radarhere]

I've created #5597 to fix 1.

[kmilos]

Thanks, that's what I had in mind as well for 1.

[kmilos]

As far as item 2 goes, would removing 530 and 532 from "core tags" in both PIL/TiffTags.py and encode.c perhaps let them be encoded properly from the ifd dictionary?

[radarhere]

I've updated the PR so that it should now cover 2 as well.

[radarhere]

In combination with #5588, that resolves this.