give icc_import / _export / _transform access to the new fallback profiles

[jcupitt]

libvips now has a built-in fallback CMYK profile for vips_CMYK2XYZ(). This should be available to vips_icc_import() etc, as well, perhaps by giving the special string cmyk as a profile filename.

We could add an sRGB fallback profile as well.

See #1186

[jcupitt]

There's a branch here with this added:

https://github.com/libvips/libvips/tree/add-icc-fallbacks

It includes a built-in srgb profile as well as a cmyk one. Anywhere where icc_* operations take a profile filename, you can use the case-insensitive name of one of these files (without a suffix) instead if you wish:

https://github.com/libvips/libvips/tree/add-icc-fallbacks/libvips/colour/profiles

Run it like this:

vips icc_import k2.jpg x.v --input-profile=srgb
vips icc_transform in.jpg out.jpg cmyk --input-profile=srgb

Still to do:

• Some of the load/save operations can take profile filenames too. They should allow a fallback as well.
• We should probably have an operation that returns a named profile as a blob. This would let language bindings add profiles with get / set.

[jcupitt]

Added vips_profile_load() to load a named profile. You can use profile_load from any binding.

[jcupitt]

And the savers all use vips_profile_load() to attach ICC profiles to images.

I think this is done!

[jcupitt]

OK, merged to master.

[kleisauke]

Does this work for vips_icc_export?

Because this command seems to fail for me (on master):

wget https://ory.weserv.nl/zebra.jpg
vips icc_export zebra.jpg x.v --output-profile=srgb

vips__file_open_read: unable to open file "srgb" for reading
unix error: No such file or directory

[jcupitt]

Oh, odd, yes, it should do. I expect I messed up, I'll have a look.

[jcupitt]

Yes, there was some code code that hadn't been moved to the new thing. Should be fixed now. Thanks!

[kleisauke]

It still seems to refuse to produce output via the fallback ICC profile (on master). For example:

[kleisauke@pc-kaw ~]$ wget https://github.com/lovell/sharp/raw/master/test/fixtures/cielab-dagams.tiff
[kleisauke@pc-kaw ~]$ vips colourspace cielab-dagams.tiff cielab-dagams.v srgb

(vips:30470): VIPS-WARNING **: 13:54:35.304: Incompatible type for "RichTIFFIPTC"; tag ignored
[kleisauke@pc-kaw ~]$ vips icc_transform cielab-dagams.v x.v srgb --input-profile=srgb --intent=perceptual --embedded=true

(vips:30490): VIPS-WARNING **: 13:54:41.133: profile colourspace differs from image
icc_transform: no input profile

(same output with vipsthumbnail cielab-dagams.tiff --size 128 --iprofile srgb --eprofile srgb)

This worked fine on vips 8.7.4:

[kleisauke@pc-kaw ~]$ vips colourspace cielab-dagams.tiff cielab-dagams.v srgb

(vips:9654): VIPS-WARNING **: 14:01:24.103: Incompatible type for "RichTIFFIPTC"; tag ignored
[kleisauke@pc-kaw ~]$ wget https://github.com/libvips/nip2/raw/master/share/nip2/data/sRGB.icm
[kleisauke@pc-kaw ~]$ vips icc_transform cielab-dagams.v x.v sRGB.icm --input-profile=sRGB.icm --intent=perceptual --embedded=true

(vips:9794): VIPS-WARNING **: 14:01:28.219: embedded profile colourspace differs from image

See #730 for more background information regarding this cielab-dagams.tiff image.

(I'm not sure if I had to open a new issue for this)