Return an error when an APNG header is encountered

src/png.rs

@@ -239,6 +239,8 @@ impl PngData {
             };
             if header.0 == "IDAT" {
                 idat_headers.extend(header.1);
+            } else if header.0 == "acTL" {
+                return Err(PngError::new("APNG files are not (yet) supported"));
             } else {
                 aux_headers.insert(header.0, header.1);
             }

tests/lib.rs

@@ -31,6 +31,19 @@ fn optimize_from_memory_corrupted() {
     assert!(result.is_err());
 }
 
+#[test]
+fn optimize_from_memory_apng() {
+    let mut in_file = File::open("tests/files/apng_file.png").unwrap();
+    let mut in_file_buf: Vec<u8> = Vec::new();
+    in_file.read_to_end(&mut in_file_buf).unwrap();
+
+    let mut opts: oxipng::Options = Default::default();
+    opts.verbosity = Some(1);
+
+    let result = oxipng::optimize_from_memory(&in_file_buf, &opts);
+    assert!(result.is_err());
+}
+
 #[test]
 fn optimize() {
     let mut opts: oxipng::Options = Default::default();
@@ -48,3 +61,12 @@ fn optimize_corrupted() {
     let result = oxipng::optimize(Path::new("tests/files/corrupted_header.png"), &opts);
     assert!(result.is_err());
 }
+
+#[test]
+fn optimize_apng() {
+    let mut opts: oxipng::Options = Default::default();
+    opts.verbosity = Some(1);
+
+    let result = oxipng::optimize(Path::new("tests/files/apng_file.png"), &opts);
+    assert!(result.is_err());
+}