From e1aeb00be9138adcfa5fc7b748037e1ea5b7390b Mon Sep 17 00:00:00 2001
From: mtlcl410 <2368091+mtlcl410@users.noreply.github.com>
Date: Sun, 18 Oct 2026 14:21:35 +0800
Subject: [PATCH] fix(render): apply the JP2 palette of a JPX image with no
 /ColorSpace (#3179)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

hayro-syntax decoded every JPX image with resolve_palette_indices off. That
is right when the image dictionary gives a /ColorSpace (an /Indexed space
needs the raw indices), but with no /ColorSpace the colours come from the
JP2 header (ISO 32000-2 §7.4.9) and nothing applied its palette: the
indices were drawn as a gray image. The palette is now resolved exactly
when the dictionary has no /ColorSpace.

Two unit tests decode a 4x2 palette JP2 written for the test: without a
colour space it is red/blue RGB, with /Indexed the raw indices stay.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RUNQSPVXx3dDBabRZHAnjz
---
 vendor/README.md                      |  7 +++
 vendor/hayro-syntax/src/filter/jpx.rs | 64 ++++++++++++++++++++++++++-
 2 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/vendor/README.md b/vendor/README.md
index 7b2c37f02..95b9418ab 100644
--- a/vendor/README.md
+++ b/vendor/README.md
@@ -41,6 +41,13 @@ Covered by `raster::tests::tiff_predictor_packed_rgb_rows_keep_their_byte_bounda
 horizontal differencing and an 8-bit control) and
 `raster::tests::tiff_predictor_packed_rgb_image_renders_every_row`.
 
+JPEG 2000 palettes (#3179): `hayro-syntax::filter::jpx::decode` applies a JP2 palette (`pclr`)
+when the image dictionary has no `/ColorSpace`, since the colour then comes from the JP2 header
+(ISO 32000-2 §7.4.9). With a `/ColorSpace` the raw indices are kept, as an `/Indexed` space needs.
+Without the patch a palette image with no `/ColorSpace` was drawn as its indices, in gray.
+Covered by `filter::jpx::tests::jpx_palette_is_applied_without_a_color_space` and
+`filter::jpx::tests::jpx_palette_indices_stay_raw_for_an_indexed_color_space`.
+
 Text extraction: hayro-interpret exposes `OutlineGlyph::is_vertical` from a Type0 font’s CMap writing mode. PdfCraft follows negative glyph-space y for WMode 1 so upright vertical columns can be searched (#126).
 
 Lab Bradford follow-up to #1237: Lab adapts XYZ to D65 with white-point ratios
diff --git a/vendor/hayro-syntax/src/filter/jpx.rs b/vendor/hayro-syntax/src/filter/jpx.rs
index 74efd8b31..f3a631f0c 100644
--- a/vendor/hayro-syntax/src/filter/jpx.rs
+++ b/vendor/hayro-syntax/src/filter/jpx.rs
@@ -21,7 +21,10 @@ pub(crate) fn decode(data: &[u8], params: &ImageDecodeParams) -> Option<FilterRe
     use crate::object::stream::ImageColorSpace;
 
     let settings = DecodeSettings {
-        resolve_palette_indices: false,
+        // PdfCraft patch: (#3179) with no /ColorSpace in the image dictionary the colours come from
+        // the JP2 header (ISO 32000-2 §7.4.9), so its palette (`pclr`) is applied here; with a
+        // /ColorSpace the header colour data is ignored, and an /Indexed space takes the raw indices.
+        resolve_palette_indices: params.num_components.is_none(),
         strict: false,
         target_resolution: params.target_dimension,
     };
@@ -221,8 +224,10 @@ fn scale(
 
 #[cfg(test)]
 mod tests {
-    use super::{scale, without_refused_enumerated_colour};
+    use super::{decode, scale, without_refused_enumerated_colour};
+
     use crate::bit_reader::{BitReader, bit_mask};
+    use crate::object::stream::{ImageColorSpace, ImageDecodeParams};
     use alloc::vec::Vec;
 
     #[test]
@@ -357,5 +362,60 @@ mod tests {
             data[at..at + 4].copy_from_slice(&bad.to_be_bytes());
             assert_eq!(without_refused_enumerated_colour(&data), None, "{bad:#x}");
         }
+
+    /// A 4x2 JP2 written for this test: one 8-bit component whose samples (0, 1) index a
+    /// two-entry sRGB palette (`pclr` + `cmap`): red, then blue. Rows: 0 1 0 1 / 1 0 1 0.
+    const PALETTE_JP2: &[u8] = &[
+        0x00, 0x00, 0x00, 0x0c, 0x6a, 0x50, 0x20, 0x20, 0x0d, 0x0a, 0x87, 0x0a, 0x00, 0x00, 0x00,
+        0x14, 0x66, 0x74, 0x79, 0x70, 0x6a, 0x70, 0x32, 0x20, 0x00, 0x00, 0x00, 0x00, 0x6a, 0x70,
+        0x32, 0x20, 0x00, 0x00, 0x00, 0x55, 0x6a, 0x70, 0x32, 0x68, 0x00, 0x00, 0x00, 0x16, 0x69,
+        0x68, 0x64, 0x72, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x04, 0x00, 0x01, 0x07, 0x07,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x0f, 0x63, 0x6f, 0x6c, 0x72, 0x01, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x10, 0x00, 0x00, 0x00, 0x14, 0x70, 0x63, 0x6c, 0x72, 0x00, 0x02, 0x03, 0x07, 0x07,
+        0x07, 0xff, 0x00, 0x00, 0x00, 0x00, 0xff, 0x00, 0x00, 0x00, 0x14, 0x63, 0x6d, 0x61, 0x70,
+        0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x02, 0x00, 0x00, 0x00,
+        0x8c, 0x6a, 0x70, 0x32, 0x63, 0xff, 0x4f, 0xff, 0x51, 0x00, 0x29, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x04, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x01, 0x07, 0x01, 0x01, 0xff, 0x52, 0x00, 0x0c, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01,
+        0x04, 0x04, 0x00, 0x01, 0xff, 0x5c, 0x00, 0x07, 0x40, 0x40, 0x48, 0x48, 0x50, 0xff, 0x64,
+        0x00, 0x25, 0x00, 0x01, 0x43, 0x72, 0x65, 0x61, 0x74, 0x65, 0x64, 0x20, 0x62, 0x79, 0x20,
+        0x4f, 0x70, 0x65, 0x6e, 0x4a, 0x50, 0x45, 0x47, 0x20, 0x76, 0x65, 0x72, 0x73, 0x69, 0x6f,
+        0x6e, 0x20, 0x32, 0x2e, 0x35, 0x2e, 0x34, 0xff, 0x90, 0x00, 0x0a, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x17, 0x00, 0x01, 0xff, 0x93, 0xcf, 0xb4, 0x08, 0x08, 0x67, 0x90, 0x07, 0x41, 0x08,
+        0xff, 0xd9,
+    ];
+
+    /// #3179: with no `/ColorSpace` in the image dictionary, the JP2 palette gives the colours. The
+    /// raw indices (0 and 1) used to come back as a gray image, drawn as noise.
+    #[test]
+    fn jpx_palette_is_applied_without_a_color_space() {
+        let params = ImageDecodeParams {
+            width: 4,
+            height: 2,
+            ..ImageDecodeParams::default()
+        };
+        let result = decode(PALETTE_JP2, &params).unwrap();
+        let image = result.image_data.unwrap();
+        assert!(matches!(image.color_space, Some(ImageColorSpace::Rgb)));
+        let red = [255, 0, 0];
+        let blue = [0, 0, 255];
+        let expected: Vec<u8> = [red, blue, red, blue, blue, red, blue, red].concat();
+        assert_eq!(&*result.data, &expected[..]);
+    }
+
+    /// With an `/Indexed` colour space in the dictionary, the PDF supplies the palette, so the raw
+    /// indices are what the image holds.
+    #[test]
+    fn jpx_palette_indices_stay_raw_for_an_indexed_color_space() {
+        let params = ImageDecodeParams {
+            is_indexed: true,
+            num_components: Some(1),
+            width: 4,
+            height: 2,
+            ..ImageDecodeParams::default()
+        };
+        let result = decode(PALETTE_JP2, &params).unwrap();
+        assert_eq!(&*result.data, &[0, 1, 0, 1, 1, 0, 1, 0][..]);
     }
 }