From 44d170f059d079dddbef7db6684722a651c8506c Mon Sep 17 00:00:00 2001
From: bflatastic <bombayapirat@gmail.com>
Date: Tue, 13 Oct 2026 07:35:32 +0700
Subject: [PATCH] PDF import: pattern swatches read inside an alpha mask keep
 their images; a luminosity mask test

---
 crates/pdf/src/import.rs                |  7 ++++++-
 crates/pdf/src/tests_import_fidelity.rs | 27 +++++++++++++++++--------
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/crates/pdf/src/import.rs b/crates/pdf/src/import.rs
index 1f1da133..bac31b72 100644
--- a/crates/pdf/src/import.rs
+++ b/crates/pdf/src/import.rs
@@ -1340,10 +1340,15 @@ impl<'p> Builder<'p> {
         {
             return Some(Paint::Pattern { pattern: name.clone(), xf });
         }
+        // A swatch is shared with uses outside an alpha mask, and pattern paints keep their
+        // colours there: its images are read as they are.
+        let white = std::mem::take(&mut self.white_images);
         let art = self.nested(Rect::ZERO, |b| {
             // A cell whose content can't be decoded is empty.
             let _ = t.interpret(b, Affine::IDENTITY, stroke);
-        })?;
+        });
+        self.white_images = white;
+        let art = art?;
         let sig = paints(&art);
         let entry = self.pattern_keys.entry(key).or_default();
         entry.0 += 1;
diff --git a/crates/pdf/src/tests_import_fidelity.rs b/crates/pdf/src/tests_import_fidelity.rs
index 62e60f43..4a9a1acf 100644
--- a/crates/pdf/src/tests_import_fidelity.rs
+++ b/crates/pdf/src/tests_import_fidelity.rs
@@ -78,11 +78,9 @@ fn the_mask(d: &Document) -> (Node, OpacityMask) {
     (n, m)
 }
 
-/// An alpha soft mask whose art is an image with its own alpha (cairo, and so Inkscape, rasterizes
-/// masks so): the image is read white with that alpha, so the mask's luminance is the alpha, not
-/// the image's colour.
-#[test]
-fn an_alpha_soft_mask_of_an_image_uses_the_images_alpha() {
+/// The two pixels of the image a soft mask of kind `s` draws: black, opaque on the left and clear
+/// on the right (its own `/SMask`).
+fn mask_image_pixels(s: &str) -> [[u8; 4]; 2] {
     let g = first_extra(1);
     let group = stream(
         &format!(
@@ -91,7 +89,6 @@ fn an_alpha_soft_mask_of_an_image_uses_the_images_alpha() {
         ),
         "q 100 0 0 100 0 0 cm /Im0 Do Q",
     );
-    // Black pixels, opaque on the left and clear on the right.
     let image = stream(
         &format!(
             "/Type /XObject /Subtype /Image /Width 2 /Height 1 /ColorSpace /DeviceRGB /BitsPerComponent 8 /Filter /ASCIIHexDecode /SMask {} 0 R",
@@ -103,7 +100,7 @@ fn an_alpha_soft_mask_of_an_image_uses_the_images_alpha() {
         stream("/Type /XObject /Subtype /Image /Width 2 /Height 1 /ColorSpace /DeviceGray /BitsPerComponent 8 /Filter /ASCIIHexDecode", "FF00>");
     let bytes = one_page(
         "/GS0 gs 1 0 0 rg 0 0 100 100 re f",
-        &format!("/ExtGState << /GS0 << /SMask << /Type /Mask /S /Alpha /G {g} 0 R >> >> >>"),
+        &format!("/ExtGState << /GS0 << /SMask << /Type /Mask /S /{s} /G {g} 0 R >> >> >>"),
         &[&group, &image, &smask],
     );
     let d = open(&bytes);
@@ -116,7 +113,21 @@ fn an_alpha_soft_mask_of_an_image_uses_the_images_alpha() {
     });
     let [key] = keys.as_slice() else { panic!("one image in the mask art: {keys:?}") };
     let px = image::load_from_memory(&d.images[key].bytes).unwrap().to_rgba8();
-    assert_eq!((px.get_pixel(0, 0).0, px.get_pixel(1, 0).0), ([255, 255, 255, 255], [255, 255, 255, 0]));
+    [px.get_pixel(0, 0).0, px.get_pixel(1, 0).0]
+}
+
+/// An alpha soft mask whose art is an image with its own alpha (some PDF writers rasterize masks
+/// so): the image is read white with that alpha, so the mask's luminance is the alpha, not the
+/// image's colour (ISO 32000-1 11.5.2: an alpha mask takes the group's alpha, not its colour).
+#[test]
+fn an_alpha_soft_mask_of_an_image_uses_the_images_alpha() {
+    assert_eq!(mask_image_pixels("Alpha"), [[255, 255, 255, 255], [255, 255, 255, 0]]);
+}
+
+/// A luminosity soft mask takes the group's colour (ISO 32000-1 11.5.3): its image stays black.
+#[test]
+fn a_luminosity_soft_mask_of_an_image_keeps_the_images_colour() {
+    assert_eq!(mask_image_pixels("Luminosity"), [[0, 0, 0, 255], [0, 0, 0, 0]]);
 }
 
 #[test]