LibGfx/JBIG2+jbig2-from-json: Write intermediate halftone, text regions

nico · nico · commit 217364b6c436 · 2025-11-18T07:51:05.000-05:00
Similar to #26410, the challenge with refining halftone and text regions is that the writer needs to know the decoded halftone and text region bitmap. That data is easily available in the loader, but not in the writer. Similar to #26410, the approach is to call into the *loader* with a list of segments needed to decode the intermediate region's data. ...and then some minor plumbing to hook up the intermediate region types in jbig2-from-json. With this, we can write all region segment types :^)
diff --git a/Userland/Libraries/LibGfx/ImageFormats/JBIG2Writer.cpp b/Userland/Libraries/LibGfx/ImageFormats/JBIG2Writer.cpp
@@ -2275,13 +2275,19 @@ static ErrorOr<void> encode_generic_refinement_region(JBIG2::GenericRefinementRe
     if (header.referred_to_segments.size() > 1)
         return Error::from_string_literal("JBIG2Writer: Generic refinement region must refer to at most one segment");
 
-    auto collect_related_segments = [&context](u32 page, u32 segment_number) {
+    enum class CollectionBehavior {
+        ExcludeSelf,
+        IncludeSelf,
+    };
+    auto collect_related_segments = [&context](u32 page, u32 segment_number, CollectionBehavior behavior) {
         Vector<ReadonlyBytes> preceding_segments_on_same_page;
         bool found = false;
         for (auto const& segment : context.segments) {
             if (segment.header.page_association == 0 || segment.header.page_association == page) {
                 auto const& data = context.segment_data_by_id.get(segment.header.segment_number);
                 if (segment.header.segment_number == segment_number) {
+                    if (behavior == CollectionBehavior::IncludeSelf)
+                        preceding_segments_on_same_page.append(data->data);
                     found = true;
                     break;
                 }
@@ -2303,12 +2309,21 @@ static ErrorOr<void> encode_generic_refinement_region(JBIG2::GenericRefinementRe
             auto const& referred_to_segment = *maybe_segment.value();
 
             return TRY(referred_to_segment.data.visit(
+                           [&]<OneOf<JBIG2::IntermediateTextRegionSegmentData, JBIG2::IntermediateHalftoneRegionSegmentData> T>(T const&) -> ErrorOr<NonnullRefPtr<BilevelImage>> {
+                               auto related_segments_on_same_page = collect_related_segments(referred_to_segment.header.page_association, referred_to_segment.header.segment_number, CollectionBehavior::IncludeSelf);
+                               auto bitmap = TRY(JBIG2ImageDecoderPlugin::decode_embedded_intermediate_region_segment(related_segments_on_same_page, referred_to_segment.header.segment_number));
+                               return bitmap;
+                           },
+
+                           // Optimization: IntermediateGenericRegionSegmentData, IntermediateGenericRefinementRegionSegmentData could also use
+                           // the implementation above, but since we happen to have the final bitmap at hand for them, just return it immediately.
                            [](JBIG2::IntermediateGenericRegionSegmentData const& generic_region_wrapper) -> ErrorOr<NonnullRefPtr<BilevelImage>> {
                                return generic_region_wrapper.generic_region.image;
                            },
                            [](JBIG2::IntermediateGenericRefinementRegionSegmentData const& generic_refinement_region_wrapper) -> ErrorOr<NonnullRefPtr<BilevelImage>> {
                                return generic_refinement_region_wrapper.generic_refinement_region.image;
                            },
+
                            [](auto const&) -> ErrorOr<NonnullRefPtr<BilevelImage>> {
                                return Error::from_string_literal("JBIG2Writer: Generic refinement region can only refer to intermediate region segments");
                            }))
@@ -2319,7 +2334,7 @@ static ErrorOr<void> encode_generic_refinement_region(JBIG2::GenericRefinementRe
         //  contents of the page buffer (see clause 8), restricted to the area of the page buffer specified by this segment's region
         //  segment information field."
         VERIFY(header.referred_to_segments.size() == 0);
-        auto preceding_segments_on_same_page = collect_related_segments(header.page_association, header.segment_number);
+        auto preceding_segments_on_same_page = collect_related_segments(header.page_association, header.segment_number, CollectionBehavior::ExcludeSelf);
         auto bitmap = TRY(JBIG2ImageDecoderPlugin::decode_embedded(preceding_segments_on_same_page));
         return bitmap->subbitmap(generic_refinement_region.region_segment_information.rect());
     }());
@@ -2550,6 +2565,10 @@ static ErrorOr<SerializedSegmentData> encode_segment(JBIG2::SegmentData const& s
             TRY(encode_text_region(text_region_wrapper.text_region, segment_data.header, context, scratch_buffer));
             return scratch_buffer;
         },
+        [&scratch_buffer, &segment_data, &context](JBIG2::IntermediateTextRegionSegmentData const& text_region_wrapper) -> ErrorOr<ReadonlyBytes> {
+            TRY(encode_text_region(text_region_wrapper.text_region, segment_data.header, context, scratch_buffer));
+            return scratch_buffer;
+        },
         [&scratch_buffer](JBIG2::PatternDictionarySegmentData const& pattern_dictionary) -> ErrorOr<ReadonlyBytes> {
             TRY(encode_pattern_dictionary(pattern_dictionary, scratch_buffer));
             return scratch_buffer;
@@ -2562,6 +2581,10 @@ static ErrorOr<SerializedSegmentData> encode_segment(JBIG2::SegmentData const& s
             TRY(encode_halftone_region(halftone_region_wrapper.halftone_region, segment_data.header, context, scratch_buffer));
             return scratch_buffer;
         },
+        [&scratch_buffer, &segment_data, &context](JBIG2::IntermediateHalftoneRegionSegmentData const& halftone_region_wrapper) -> ErrorOr<ReadonlyBytes> {
+            TRY(encode_halftone_region(halftone_region_wrapper.halftone_region, segment_data.header, context, scratch_buffer));
+            return scratch_buffer;
+        },
         [&scratch_buffer](JBIG2::ImmediateGenericRegionSegmentData const& generic_region_wrapper) -> ErrorOr<ReadonlyBytes> {
             TRY(encode_generic_region(generic_region_wrapper.generic_region, scratch_buffer));
             return scratch_buffer;
@@ -2619,9 +2642,11 @@ static ErrorOr<SerializedSegmentData> encode_segment(JBIG2::SegmentData const& s
         [](JBIG2::SymbolDictionarySegmentData const&) { return JBIG2::SegmentType::SymbolDictionary; },
         [](JBIG2::ImmediateTextRegionSegmentData const&) { return JBIG2::SegmentType::ImmediateTextRegion; },
         [](JBIG2::ImmediateLosslessTextRegionSegmentData const&) { return JBIG2::SegmentType::ImmediateLosslessTextRegion; },
+        [](JBIG2::IntermediateTextRegionSegmentData const&) { return JBIG2::SegmentType::IntermediateTextRegion; },
         [](JBIG2::PatternDictionarySegmentData const&) { return JBIG2::SegmentType::PatternDictionary; },
         [](JBIG2::ImmediateHalftoneRegionSegmentData const&) { return JBIG2::SegmentType::ImmediateHalftoneRegion; },
         [](JBIG2::ImmediateLosslessHalftoneRegionSegmentData const&) { return JBIG2::SegmentType::ImmediateLosslessHalftoneRegion; },
+        [](JBIG2::IntermediateHalftoneRegionSegmentData const&) { return JBIG2::SegmentType::IntermediateHalftoneRegion; },
         [](JBIG2::ImmediateGenericRegionSegmentData const&) { return JBIG2::SegmentType::ImmediateGenericRegion; },
         [](JBIG2::ImmediateLosslessGenericRegionSegmentData const&) { return JBIG2::SegmentType::ImmediateLosslessGenericRegion; },
         [](JBIG2::IntermediateGenericRegionSegmentData const&) { return JBIG2::SegmentType::IntermediateGenericRegion; },
diff --git a/Userland/Libraries/LibGfx/ImageFormats/JBIG2Writer.h b/Userland/Libraries/LibGfx/ImageFormats/JBIG2Writer.h
@@ -149,6 +149,10 @@ struct ImmediateLosslessTextRegionSegmentData {
     TextRegionSegmentData text_region;
 };
 
+struct IntermediateTextRegionSegmentData {
+    TextRegionSegmentData text_region;
+};
+
 struct PatternDictionarySegmentData {
     u8 flags { 0 };
     u8 pattern_width { 0 };
@@ -188,6 +192,10 @@ struct ImmediateLosslessHalftoneRegionSegmentData {
     HalftoneRegionSegmentData halftone_region;
 };
 
+struct IntermediateHalftoneRegionSegmentData {
+    HalftoneRegionSegmentData halftone_region;
+};
+
 struct GenericRegionSegmentData {
     RegionSegmentInformationField region_segment_information {};
     u8 flags { 0 };
@@ -263,9 +271,11 @@ struct SegmentData {
         SymbolDictionarySegmentData,
         ImmediateTextRegionSegmentData,
         ImmediateLosslessTextRegionSegmentData,
+        IntermediateTextRegionSegmentData,
         PatternDictionarySegmentData,
         ImmediateHalftoneRegionSegmentData,
         ImmediateLosslessHalftoneRegionSegmentData,
+        IntermediateHalftoneRegionSegmentData,
         ImmediateGenericRegionSegmentData,
         ImmediateLosslessGenericRegionSegmentData,
         IntermediateGenericRegionSegmentData,
diff --git a/Userland/Utilities/jbig2-from-json.cpp b/Userland/Utilities/jbig2-from-json.cpp
@@ -1324,6 +1324,11 @@ static ErrorOr<Gfx::JBIG2::SegmentData> jbig2_immediate_lossless_text_region_fro
     return Gfx::JBIG2::SegmentData { header, Gfx::JBIG2::ImmediateLosslessTextRegionSegmentData { TRY(jbig2_text_region_from_json(options, object)) } };
 }
 
+static ErrorOr<Gfx::JBIG2::SegmentData> jbig2_intermediate_text_region_from_json(ToJSONOptions const& options, Gfx::JBIG2::SegmentHeaderData const& header, Optional<JsonObject const&> object)
+{
+    return Gfx::JBIG2::SegmentData { header, Gfx::JBIG2::IntermediateTextRegionSegmentData { TRY(jbig2_text_region_from_json(options, object)) } };
+}
+
 static ErrorOr<u8> jbig2_pattern_dictionary_flags_from_json(JsonObject const& object)
 {
     u8 flags = 0;
@@ -1764,6 +1769,11 @@ static ErrorOr<Gfx::JBIG2::SegmentData> jbig2_immediate_lossless_halftone_region
     return Gfx::JBIG2::SegmentData { header, Gfx::JBIG2::ImmediateLosslessHalftoneRegionSegmentData { TRY(jbig2_halftone_region_from_json(options, object)) } };
 }
 
+static ErrorOr<Gfx::JBIG2::SegmentData> jbig2_intermediate_halftone_region_from_json(ToJSONOptions const& options, Gfx::JBIG2::SegmentHeaderData const& header, Optional<JsonObject const&> object)
+{
+    return Gfx::JBIG2::SegmentData { header, Gfx::JBIG2::IntermediateHalftoneRegionSegmentData { TRY(jbig2_halftone_region_from_json(options, object)) } };
+}
+
 static ErrorOr<u8> jbig2_generic_region_flags_from_json(JsonObject const& object)
 {
     u8 flags = 0;
@@ -2664,12 +2674,16 @@ static ErrorOr<Gfx::JBIG2::SegmentData> jbig2_segment_from_json(ToJSONOptions co
         return jbig2_immediate_text_region_from_json(options, header, segment_data_object);
     if (type_string == "lossless_text_region")
         return jbig2_immediate_lossless_text_region_from_json(options, header, segment_data_object);
+    if (type_string == "intermediate_text_region")
+        return jbig2_intermediate_text_region_from_json(options, header, segment_data_object);
     if (type_string == "pattern_dictionary")
         return jbig2_pattern_dictionary_from_json(options, header, segment_data_object);
     if (type_string == "halftone_region")
         return jbig2_immediate_halftone_region_from_json(options, header, segment_data_object);
     if (type_string == "lossless_halftone_region")
         return jbig2_immediate_lossless_halftone_region_from_json(options, header, segment_data_object);
+    if (type_string == "intermediate_halftone_region")
+        return jbig2_intermediate_halftone_region_from_json(options, header, segment_data_object);
     if (type_string == "generic_region")
         return jbig2_immediate_generic_region_from_json(options, header, segment_data_object);
     if (type_string == "lossless_generic_region")
