From 88b49a639e2204be7cfd0c4c9b13376b014de217 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Wed, 24 Jan 2024 11:44:09 -0500
Subject: [PATCH] LibGfx/ICC: Add a convert_cmyk_image() method

It converts from a CMYKBitmap to an (rgb) bitmap, using a real
color profile.

The API design here isn't super scalable (what if we want to also
handle grayscale inputs? What if we also want to convert _to_ cmyk
or grayscale?), but we have to start somewhere. Uses of this can
inform future API improvements.
---
 Userland/Libraries/LibGfx/ICC/Profile.cpp | 26 +++++++++++++++++++++++
 Userland/Libraries/LibGfx/ICC/Profile.h   |  1 +
 2 files changed, 27 insertions(+)

diff --git a/Userland/Libraries/LibGfx/ICC/Profile.cpp b/Userland/Libraries/LibGfx/ICC/Profile.cpp
index 0f5df41264..44503392ae 100644
--- a/Userland/Libraries/LibGfx/ICC/Profile.cpp
+++ b/Userland/Libraries/LibGfx/ICC/Profile.cpp
@@ -6,6 +6,7 @@
 
 #include <AK/Endian.h>
 #include <LibGfx/CIELAB.h>
+#include <LibGfx/CMYKBitmap.h>
 #include <LibGfx/ICC/BinaryFormat.h>
 #include <LibGfx/ICC/Profile.h>
 #include <LibGfx/ICC/Tags.h>
@@ -1660,6 +1661,31 @@ ErrorOr<void> Profile::convert_image(Gfx::Bitmap& bitmap, Profile const& source_
     return {};
 }
 
+ErrorOr<void> Profile::convert_cmyk_image(Bitmap& out, CMYKBitmap const& in, Profile const& source_profile) const
+{
+    if (out.size() != in.size())
+        return Error::from_string_literal("ICC::Profile::convert_cmyk_image: out and in must have the same dimensions");
+
+    // Might fail if `out` has a scale_factor() != 1.
+    if (out.data_size() != in.data_size())
+        return Error::from_string_literal("ICC::Profile::convert_cmyk_image: out and in must have the same buffer size");
+
+    static_assert(sizeof(ARGB32) == sizeof(CMYK));
+    ARGB32* out_data = out.begin();
+    CMYK const* in_data = const_cast<CMYKBitmap&>(in).begin();
+
+    for (size_t i = 0; i < in.data_size() / sizeof(CMYK); ++i) {
+        u8 cmyk[] = { in_data[i].c, in_data[i].m, in_data[i].y, in_data[i].k };
+        auto pcs = TRY(source_profile.to_pcs(cmyk));
+
+        u8 rgb[3];
+        TRY(from_pcs(source_profile, pcs, rgb));
+        out_data[i] = Color(rgb[0], rgb[1], rgb[2]).value();
+    }
+
+    return {};
+}
+
 XYZ const& Profile::red_matrix_column() const { return xyz_data(redMatrixColumnTag); }
 XYZ const& Profile::green_matrix_column() const { return xyz_data(greenMatrixColumnTag); }
 XYZ const& Profile::blue_matrix_column() const { return xyz_data(blueMatrixColumnTag); }
diff --git a/Userland/Libraries/LibGfx/ICC/Profile.h b/Userland/Libraries/LibGfx/ICC/Profile.h
index 5826c5ec4e..91a6fc06dc 100644
--- a/Userland/Libraries/LibGfx/ICC/Profile.h
+++ b/Userland/Libraries/LibGfx/ICC/Profile.h
@@ -275,6 +275,7 @@ public:
     ErrorOr<CIELAB> to_lab(ReadonlyBytes) const;
 
     ErrorOr<void> convert_image(Bitmap&, Profile const& source_profile) const;
+    ErrorOr<void> convert_cmyk_image(Bitmap&, CMYKBitmap const&, Profile const& source_profile) const;
 
     // Only call these if you know that this is an RGB matrix-based profile.
     XYZ const& red_matrix_column() const;