In XYZ space, gray doesn't have three equal values. Instead, it is
a line through the whitepoint.
(Multiplying by the whitepoint has the same effect as multiplying
the sRGB matrix with a (g, g, g) vector, since the numbers on
the matrix's rows add up to the whitepoint.)
Fixes the very slight red tint on all the figures in chapter 4
of the PDF 1.7 spec.
This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).
This commit is auto-generated:
$ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
Meta Ports Ladybird Tests Kernel)
$ perl -pie 's/\bDeprecatedString\b/ByteString/g;
s/deprecated_string/byte_string/g' $xs
$ clang-format --style=file -i \
$(git diff --name-only | grep \.cpp\|\.h)
$ gn format $(git ls-files '*.gn' '*.gni')
mft1 and mft2 tags are very similar. The only difference is that
mft1 uses an u8 lookup table, while mft2 uses a u16 lookup table.
This means their PCS lookup encodings are different, and mft2 uses a
PCSLAB encoding that's different from other places in the v4 spec.
If one profile uses PCSXYZ and the other PCSLAB as connection space,
we now do the necessary XYZ/LAB conversion.
With this and the previous commits, we can now convert from profiles
that use PCSLAB with mAB, such as stress.jpeg from
https://littlecms.com/blog/2020/09/09/browser-check/ :
% Build/lagom/icc --name sRGB --reencode-to serenity-sRGB.icc
% Build/lagom/bin/image -o out.png \
--convert-to-color-profile serenity-sRGB.icc \
~/src/jpegfiles/stress.jpeg
ICC profiles work by transforming from the input color space
(one of many: RGB, CMYK, YUV, etc) to a "profile connection space" (PCS)
and then from there to the output color space.
However, there's not one but two possible profile connection spaces,
PCSXYZ and PCSLAB. The matrix/curve tags can only be used with PCSXYZ,
but the mAB, mBA, mft1, mft2 tags can be used with PCSLAB as well.
The PCSLAB encoding has L going from 0 to 100 and ab from -128 to 127,
instead of from 0 to 1. So they need to be scaled up at the end.
That's also the reason for the "mystery conversion factor": PCSXYZ
doesn't go from 0 to 1 either, but from 0 to 65535/32768, per ICC v4
6.3.4.2 General PCS encoding, Table 11 - PCSXYZ X, Y or Z encoding.
Between input and output are various curves (and the CLUT) that
have domain and range of 0..1. For these, the color has to be linearly
scaled to 0..1 before the curve and back to the actual range after
the curve. Doing that back-to-back is a no-op, so scaling back at
the very end is sufficient.
We will need to use ColorSpace in TagTypes.h, and it can't include
Profile.h.
Also makes Profile.cpp a bit smaller.
No behavior change, pure code move.
...as long as the mAB tag doesn't have A curves and a CLUT.
With this, we can convert images that use AToB* tags to the profile
connection space (and then from there to, say, sRGB), if the AToB* tag
uses the mAB format.
We can't yet do this if the mAB tag has A curves or a CLUT.
We can't convert back from PCS to this space yet.
We don't yet handle AToB* tags that use mft1 or mft2 instead of mAB.
There's probably a nicer way of doing this where we don't need to expand
the gray value into a full Vector3, but for now this is good enough.
Makes PDFs written by macOS 13.5.2's "Save as PDF..." feature show up.
This allows converting to a color space that uses a non-parametric
curve, for example:
Build/lagom/image -o foo.png \
--convert-to-color-profile .../profiles/sRGB-v2-micro.icc \
input.jpg
...where profiles/sRGB-v2-micro.icc is from
https://github.com/saucecontrol/Compact-ICC-Profiles/
(Parametric curves are new in ICC v4, which means all v2 profiles
use point curves.)
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.
I had missed this in 21cc0c0cb2 because this tag is missing in
"Table 32 — Tag list" in the v2 ICC spec O_o. But it's in
"6.4.26 namedColorTag".
Also add a comment pointing to a page saying that all these tags
are very deprecated and not even recommended for new v2 profiles.
(That's how I noticed that namedColorTag was missing.)
This isn't terribly useful. But some profiles, for example the ones at
https://vpifg.com/help/icc-profiles/, do contain this tag and it seems
nice to be able to dump it, just for completeness.
I haven't seen any files that contain a phosphor or colorant type
different from "Unknown", even for the Rec2020 profile on that page.
(It has x,y coordinates that match the values required for Rec2020,
but it doesn't set the phosphor or colorant type to that.)
Not terribly useful in practice either and also mostly for
completionism. But with this, we can dump all types present
in Lightroom Classic-exported jpegs :^)
These are among the permitted tag types of ATo0Tag and BToA0Tag,
which are among the required tags of most profiles. They are the
last permitted tag types for those profiles (the other are
lut8Type or lut16Type, which are already implemented).
They are pretty chonky types though, so this only implements
support for the E matrix and the CLUT. Support for the various
curves will be in a future PR.
This is a very new tag used for HDR content. The only files I know that
use it are the jpegs on https://ccameron-chromium.github.io/hdr-jpeg/
But they have an invalid ICC creation date, so `icc` can't process them.
(Commenting out the check for that does allow to print them.)
If the CIPC tag is present, it takes precedence about the actual data
in the profile and from what I understand, the ICC profile is
basically ignored. See https://www.color.org/events/HDR_experts.xalter
for background, in particular
https://www.color.org/hdr/02-Luke_Wallis.pdf (but the other talks
are very interesting too).
(PNG also has a cICP chunk that's supposed to take precedence over
iCCP.)
