YCbCr in TIFF

[Drarakel]

Reading YCbCr:
There seems to be a minor issue with the photometric info in identify. When reading YCbCr in TIFF, the PHOTOMETRIC_YCBCR case (photometric value 6) is missing, and so it defaults to "unknown":

Code: Select all

convert logo: -colorspace ycbcr -compress jpeg test_ycbcr.tif

exiftool -S -PhotometricInterpretation test_ycbcr.tif
PhotometricInterpretation: YCbCr
identify -verbose test_ycbcr.tif
...
tiff:photometric: unknown


Writing YCbCr:
One should be able to store YCbCr in TIFF with LZW compression, right? That works e.g. with the rose image:

Code: Select all

convert rose: -colorspace ycbcr -compress lzw rose-ycbcr-lzw.tif

exiftool -S -PhotometricInterpretation -Compression rose-ycbcr-lzw.tif
PhotometricInterpretation: YCbCr
Compression: LZW

convert rose-ycbcr-lzw.tif rose.jpg


But e.g. with the logo image (less than 256 colors), it fails. The photometric value is set to palette (and besides, even here, the YCbCrSubSampling tag is written):

Code: Select all

convert logo: -colorspace ycbcr -compress lzw logo-ycbcr-lzw.tif

exiftool -S -PhotometricInterpretation -Compression logo-ycbcr-lzw.tif
PhotometricInterpretation: RGB Palette
Compression: LZW

convert logo-ycbcr-lzw.tif logo.jpg


I can only read such an image with a bad workaround:
convert logo-ycbcr-lzw.tif -set colorspace YCbCr -colorspace RGB logo2.jpg

[magick]

We can reproduce the problem you reported and have a patch in ImageMagick 6.6.4-3 Beta available by sometime tomorrow. Thanks.

[Drarakel]

Awesome! Thank you for all those patches!

[Drarakel]

Works in version 6.6.4-4. Thanks again.