Merge pull request #1565 from midasmatterhorn/fix/r4-smask-bpc-shift

pdf: a soft mask at an unsupported bit depth is ignored, not fatal

crates/pdf/src/image.rs

@@ -184,6 +184,11 @@ fn mask_image(file: &File, o: &Obj, soft: bool) -> Option<(Vec<u8>, usize, usize
         return Some((data.into_iter().step_by(jpeg_n.unwrap_or(1)).take(w * h).collect(), w, h));
     }
     let bpc = if soft { file.get_num(d, "BitsPerComponent").unwrap_or(8.0) as usize } else { 1 };
+    // Like `decode()`: only 1/2/4/8/16-bit depths are supported. Anything else (notably
+    // `bpc >= 32`, where `1u32 << bpc` below would overflow) means "no usable mask".
+    if !matches!(bpc, 1 | 2 | 4 | 8 | 16) {
+        return None;
+    }
     let max = ((1u32 << bpc) - 1).max(1) as f64;
     let dec = file.get(d, "Decode").map(|x| file.nums(x)).filter(|v| v.len() >= 2);
     let v = unpack(&data, w, h, 1, bpc);

crates/pdf/src/tests_import.rs

@@ -274,11 +274,32 @@ fn inline_image_with_absurd_dimensions_falls_back_to_ei_scan() {
     assert!(!doc.skipped.is_empty());
     // A length just under `usize::MAX` passes the row math; past byte 4096 of the content the
     // caller's `start + len` would then overflow.
-    let content = format!("{}q 10 0 0 10 0 0 cm BI /W 2305843009213693440 /H 8 /CS /G /BPC 8 ID  EI Q", " ".repeat(5000));
+    let content = format!("{}q 10 0 0 10 0 0 cm BI /W 2305843009213693440 /H 8 /CS /G /BPC 8 ID \0 EI Q", " ".repeat(5000));
     let doc = parse(&page_pdf(&content, "", vec![])).unwrap();
     let _ = render(&doc);
 }
 
+#[test]
+fn smask_with_absurd_bpc_is_ignored_not_fatal() {
+    // `/BitsPerComponent 32` in a soft mask: `1u32 << bpc` must neither panic (debug)
+    // nor mistranslate samples into alpha (release); the mask is treated as absent.
+    let bytes = page_pdf(
+        "q 2 0 0 2 0 0 cm /Im Do Q",
+        "/XObject << /Im 10 0 R >>",
+        vec![
+            (
+                10,
+                "<< /Type /XObject /Subtype /Image /Width 2 /Height 2 /ColorSpace /DeviceGray /BitsPerComponent 8 /SMask 11 0 R >>".into(),
+                Some(vec![0x80; 4]),
+            ),
+            (11, "<< /Type /XObject /Subtype /Image /Width 2 /Height 2 /ColorSpace /DeviceGray /BitsPerComponent 32 >>".into(), Some(vec![0xFF; 16])),
+        ],
+    );
+    let doc = parse(&bytes).unwrap();
+    let img = render(&doc);
+    assert!(coverage(&img, 0, 0, 200, 100) > 0.0, "image still draws, opaque");
+}
+
 #[test]
 fn truncated_and_corrupt_eps_never_panic() {
     let eps = b"%!PS-Adobe-3.0 EPSF-3.0\n%%BoundingBox: 0 0 100 100\n\