From abe90db45a41de02ba8fde1f9155894ec019e51c Mon Sep 17 00:00:00 2001
From: "Dylan M. Taylor" <dylan@dylanmtaylor.com>
Date: Sun, 15 Nov 2026 17:42:47 +0000
Subject: [PATCH] Cover PNG transparency keys in opaque outline decoding

---
 crates/trace/src/opaque.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/crates/trace/src/opaque.rs b/crates/trace/src/opaque.rs
index 0bfcbf143f..7a0b87d9e0 100644
--- a/crates/trace/src/opaque.rs
+++ b/crates/trace/src/opaque.rs
@@ -326,6 +326,25 @@ mod tests {
         assert!(decode_alpha(b"not an image").is_err());
     }
 
+    #[test]
+    fn decode_alpha_expands_gray_and_rgb_png_transparency_keys() {
+        // Original synthetic 2x1 PNGs: first pixel matches tRNS; second is opaque.
+        // Generated from PNG chunks and zlib scanlines, without an external image asset.
+        let gray: &[u8] = &[
+            137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 2, 0, 0, 0, 1, 8, 0, 0, 0, 0, 209, 73, 32, 86, 0, 0, 0, 2, 116,
+            82, 78, 83, 0, 0, 118, 147, 205, 56, 0, 0, 0, 11, 73, 68, 65, 84, 120, 156, 99, 96, 168, 7, 0, 0, 130, 0, 128, 32, 18, 25, 54, 0, 0, 0,
+            0, 73, 69, 78, 68, 174, 66, 96, 130,
+        ];
+        let rgb: &[u8] = &[
+            137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 2, 0, 0, 0, 1, 8, 2, 0, 0, 0, 123, 64, 232, 221, 0, 0, 0, 6, 116,
+            82, 78, 83, 0, 255, 0, 0, 0, 0, 164, 194, 192, 29, 0, 0, 0, 15, 73, 68, 65, 84, 120, 156, 99, 248, 207, 192, 192, 240, 159, 1, 0, 7, 255,
+            1, 255, 1, 127, 137, 167, 0, 0, 0, 0, 73, 69, 78, 68, 174, 66, 96, 130,
+        ];
+        for bytes in [gray, rgb] {
+            assert_eq!(decode_alpha(bytes).unwrap(), Some((2, 1, vec![0, 255])));
+        }
+    }
+
     #[test]
     fn decode_alpha_preserves_cmyk_and_lab_tiff_extra_samples() {
         use craft_image_codecs::{ChannelLayout, Format, Image};