Add apng decode test

src/codecs/png.rs

@@ -760,4 +760,22 @@ mod tests {
         let mut target = Cursor::new(vec![]);
         let _ = image.write_to(&mut target, ImageFormat::Png);
     }
+
+    #[test]
+    fn apng_decode_partial_dispose() {
+        // Verify by comparing the APNG decode result with the final frame decoded by ffmpeg.
+
+        let apng = std::fs::read("tests/images/png/bugfixes/issue#2265.png").unwrap();
+
+        let last_frame_reference_image =
+            crate::open("tests/images/png/bugfixes/issue#2265_ffmpeg_decoded_last_frame.png")
+                .unwrap();
+
+        let decoder = PngDecoder::new(Cursor::new(&apng)).unwrap();
+        let decoder = decoder.apng().unwrap();
+        let frames = decoder.into_frames().collect::<Vec<_>>();
+        let last_frame = frames.last().as_ref().unwrap().as_ref().unwrap().buffer();
+
+        assert_eq!(last_frame_reference_image.to_rgba8(), last_frame.clone());
+    }
 }