LibGfx/JPEG+CMYKBitmap: Extract the CMYK to RGB conversion code

Right now, the JPEG decoder is the only one supporting CMYK, but that
won't last for long. So, let's move the conversion to CMYKBitmap.

Userland/Libraries/LibGfx/CMYKBitmap.cpp

@@ -15,4 +15,21 @@ ErrorOr<NonnullRefPtr<CMYKBitmap>> CMYKBitmap::create_with_size(IntSize const& s
     return adopt_ref(*new CMYKBitmap(size, move(data)));
 }
 
+ErrorOr<RefPtr<Bitmap>> CMYKBitmap::to_low_quality_rgb() const
+{
+    if (!m_rgb_bitmap) {
+        m_rgb_bitmap = TRY(Bitmap::create(BitmapFormat::BGRx8888, { m_size.width(), m_size.height() }));
+
+        for (int y = 0; y < m_size.height(); ++y) {
+            for (int x = 0; x < m_size.width(); ++x) {
+                auto const& cmyk = scanline(y)[x];
+                u8 k = 255 - cmyk.k;
+                m_rgb_bitmap->scanline(y)[x] = Color((255 - cmyk.c) * k / 255, (255 - cmyk.m) * k / 255, (255 - cmyk.y) * k / 255).value();
+            }
+        }
+    }
+
+    return m_rgb_bitmap;
+}
+
 }

Userland/Libraries/LibGfx/CMYKBitmap.h

@@ -9,6 +9,7 @@
 #include <AK/ByteBuffer.h>
 #include <AK/NonnullRefPtr.h>
 #include <AK/RefCounted.h>
+#include <LibGfx/Bitmap.h>
 #include <LibGfx/Size.h>
 
 namespace Gfx {
@@ -32,6 +33,8 @@ public:
     [[nodiscard]] CMYK* begin();
     [[nodiscard]] CMYK* end();
 
+    ErrorOr<RefPtr<Bitmap>> to_low_quality_rgb() const;
+
 private:
     CMYKBitmap(IntSize const& size, ByteBuffer data)
         : m_size(size)
@@ -41,6 +44,8 @@ private:
 
     IntSize m_size;
     ByteBuffer m_data;
+
+    mutable RefPtr<Bitmap> m_rgb_bitmap;
 };
 
 inline CMYK* CMYKBitmap::scanline(int y)

Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp

@@ -1694,24 +1694,6 @@ static void invert_colors_for_adobe_images(JPEGLoadingContext const& context, Ve
     }
 }
 
-static ErrorOr<void> cmyk_to_rgb(JPEGLoadingContext& context)
-{
-    VERIFY(context.cmyk_bitmap);
-    VERIFY(!context.bitmap);
-
-    context.bitmap = TRY(Bitmap::create(BitmapFormat::BGRx8888, { context.frame.width, context.frame.height }));
-
-    for (int y = 0; y < context.frame.height; ++y) {
-        for (int x = 0; x < context.frame.width; ++x) {
-            auto const& cmyk = context.cmyk_bitmap->scanline(y)[x];
-            u8 k = 255 - cmyk.k;
-            context.bitmap->scanline(y)[x] = Color((255 - cmyk.c) * k / 255, (255 - cmyk.m) * k / 255, (255 - cmyk.y) * k / 255).value();
-        }
-    }
-
-    return {};
-}
-
 static void ycck_to_cmyk(Vector<Macroblock>& macroblocks)
 {
     // 7 - Conversions between colour encodings
@@ -2026,7 +2008,7 @@ ErrorOr<ImageFrameDescriptor> JPEGImageDecoderPlugin::frame(size_t index, Option
     }
 
     if (m_context->cmyk_bitmap && !m_context->bitmap)
-        TRY(cmyk_to_rgb(*m_context));
+        return ImageFrameDescriptor { TRY(m_context->cmyk_bitmap->to_low_quality_rgb()), 0 };
 
     return ImageFrameDescriptor { m_context->bitmap, 0 };
 }