LibPDF+LibGfx: Don't invert CMYK channels in JPEG data in PDFs

This is a hack: Ideally we'd have a CMYK Bitmap pixel format,
and we'd convert to rgb at blit time. Then we could also apply color
profiles (which for CMYK images are CMYK-based).

Also, the colors for our CMYK->RGB conversion are off for PDFs,
and we have distinct codepaths for this in Gfx::Color (for paths)
and JPEGs. So when we fix that, we'll have to fix it in two places.

But this doesn't require a lot of code and it's a huge visual
progression, so let's go with it for now.

Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp

@@ -416,15 +416,16 @@ enum class ColorTransform {
 };
 
 struct JPEGLoadingContext {
-    JPEGLoadingContext(JPEGStream jpeg_stream)
+    JPEGLoadingContext(JPEGStream jpeg_stream, JPEGDecoderOptions options)
         : stream(move(jpeg_stream))
+        , options(options)
     {
     }
 
-    static ErrorOr<NonnullOwnPtr<JPEGLoadingContext>> create(NonnullOwnPtr<Stream> stream)
+    static ErrorOr<NonnullOwnPtr<JPEGLoadingContext>> create(NonnullOwnPtr<Stream> stream, JPEGDecoderOptions options)
     {
         auto jpeg_stream = TRY(JPEGStream::create(move(stream)));
-        return make<JPEGLoadingContext>(move(jpeg_stream));
+        return make<JPEGLoadingContext>(move(jpeg_stream), options);
     }
 
     enum State {
@@ -453,6 +454,7 @@ struct JPEGLoadingContext {
     Array<i16, 4> previous_dc_values {};
     MacroblockMeta mblock_meta;
     JPEGStream stream;
+    JPEGDecoderOptions options;
 
     Optional<ColorTransform> color_transform {};
 
@@ -1640,7 +1642,8 @@ static void invert_colors_for_adobe_images(JPEGLoadingContext const& context, Ve
 
 static void cmyk_to_rgb(JPEGLoadingContext const& context, Vector<Macroblock>& macroblocks)
 {
-    invert_colors_for_adobe_images(context, macroblocks);
+    if (context.options.cmyk == JPEGDecoderOptions::CMYK::Normal)
+        invert_colors_for_adobe_images(context, macroblocks);
 
     for (u32 vcursor = 0; vcursor < context.mblock_meta.vcount; vcursor += context.vsample_factor) {
         for (u32 hcursor = 0; hcursor < context.mblock_meta.hcount; hcursor += context.hsample_factor) {
@@ -1944,9 +1947,14 @@ bool JPEGImageDecoderPlugin::sniff(ReadonlyBytes data)
 }
 
 ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> JPEGImageDecoderPlugin::create(ReadonlyBytes data)
+{
+    return create_with_options(data, {});
+}
+
+ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> JPEGImageDecoderPlugin::create_with_options(ReadonlyBytes data, JPEGDecoderOptions options)
 {
     auto stream = TRY(try_make<FixedMemoryStream>(data));
-    auto context = TRY(JPEGLoadingContext::create(move(stream)));
+    auto context = TRY(JPEGLoadingContext::create(move(stream), options));
     auto plugin = TRY(adopt_nonnull_own_or_enomem(new (nothrow) JPEGImageDecoderPlugin(move(context))));
     TRY(decode_header(*plugin->m_context));
     return plugin;

Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.h

@@ -16,10 +16,22 @@ struct JPEGLoadingContext;
 
 // For the specification, see: https://www.w3.org/Graphics/JPEG/itu-t81.pdf
 
+struct JPEGDecoderOptions {
+    enum class CMYK {
+        // For standalone jpeg files.
+        Normal,
+
+        // For jpeg data embedded in PDF files.
+        PDF,
+    };
+    CMYK cmyk { CMYK::Normal };
+};
+
 class JPEGImageDecoderPlugin : public ImageDecoderPlugin {
 public:
     static bool sniff(ReadonlyBytes);
     static ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> create(ReadonlyBytes);
+    static ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> create_with_options(ReadonlyBytes, JPEGDecoderOptions = {});
 
     virtual ~JPEGImageDecoderPlugin() override;
     virtual IntSize size() override;

Userland/Libraries/LibPDF/Filter.cpp

@@ -271,7 +271,7 @@ PDFErrorOr<ByteBuffer> Filter::decode_jbig2(ReadonlyBytes)
 PDFErrorOr<ByteBuffer> Filter::decode_dct(ReadonlyBytes bytes)
 {
     if (Gfx::JPEGImageDecoderPlugin::sniff({ bytes.data(), bytes.size() })) {
-        auto decoder = TRY(Gfx::JPEGImageDecoderPlugin::create({ bytes.data(), bytes.size() }));
+        auto decoder = TRY(Gfx::JPEGImageDecoderPlugin::create_with_options({ bytes.data(), bytes.size() }, { .cmyk = Gfx::JPEGDecoderOptions::CMYK::PDF }));
         auto frame = TRY(decoder->frame(0));
         return TRY(frame.image->serialize_to_byte_buffer());
     }