For now, only for color spaces that are supported by Profile::to_pcs()
and Profile::from_pcs(), which currently means that all matrix profiles
(but not LUT profiles) in the source color space work, and that
matrix profiles with parametric curves in the destination color
space work.
This adds Profile::convert_image(Bitmap, source_profile), and
adds a `--convert-to-color-profile file.icc` flag to `image`.
It only takes a file path, so to use it with the built-in
sRGB profile, you have to write it to a file first:
% Build/lagom/icc -n sRGB --reencode-to serenity-sRGB.icc
`image` by default writes the source image's color profile
to the output image, and most image viewers display images
looking at the profile.
For example, take `Seven_Coloured_Pencils_(rg-switch_sRGB).jpg`
from https://commons.wikimedia.org/wiki/User:Colin/BrowserTest.
It looks normal in image viewers because they apply the unusual
profile embedded in the profile. But if you run
% Build/lagom/image -o huh.png --strip-color-profile \
'Seven_Coloured_Pencils_(rg-switch_sRGB).jpeg'
and then look at huh.png, you can see how the image's colors
look like when interpreted as sRGB (which is the color space
PNG data is in if the PNG doesn't store an embedded profile).
If you now run
% Build/lagom/image -o wow.png \
--convert-to-color-profile serenity-sRGB.icc --strip-color-profile \
'Seven_Coloured_Pencils_(rg-switch_sRGB).jpeg'
this will convert that image to sRGB, but then not write
the profile to the output image (verify with `Build/lagom/icc wow.png`).
It will look correct in image viewers, since they display PNGs without
an embedded color profile as sRGB.
(This works because 'Seven_Coloured_Pencils_(rg-switch_sRGB).jpeg'
contains a matrix profile, and Serenity's built-in sRGB profile
uses a matrix profile with a parametric curve.)
This implements conversion from profile connection space to the
device-dependent color for matrix-based profiles.
It only does the inverse color transform but does not yet do the
inverse tone reproduction curve transform -- i.e. it doesn't
implement many cases (LUT transforms), and it does the one thing
it does implement incorrectly. But to vindicate the commit a bit,
it also does the incorrect thing very inefficiently.
This can be used to convert a profile-dependent color to the L*a*b*
color space.
(I'd like to use this to implement the DeltaE (CIE 2000) algorithm,
which is a metric for how similar two colors are perceived.
(And I'd like to use that to evaluate color conversion roundtrip
quality, once I've implemented full conversions.)
Only implemented for matrix profiles so far.
This API won't be fast enough to color manage images, but let's
get something working before getting something fast.
s15Fixed16Number and XYZNumber are somewhat awkwardly duplicated
in both Profile.cpp and TagTypes.cpp. Other than that, this is a
pure code move.
No behavior change.
