Upgrade Group4Reader dimensions from u16 to u32

src/decoder/stream.rs

@@ -260,9 +260,9 @@ impl<R: Read> Read for PackBitsReader<R> {
 pub struct Group4Reader<R: Read> {
     decoder: fax34::decoder::Group4Decoder<io::Bytes<io::BufReader<io::Take<R>>>>,
     line_buf: io::Cursor<Vec<u8>>,
-    height: u16,
+    height: u32,
     width: u16,
-    y: u16,
+    y: u32,
 }
 
 #[cfg(feature = "fax")]
@@ -273,7 +273,7 @@ impl<R: Read> Group4Reader<R> {
         compressed_length: u64,
     ) -> crate::TiffResult<Self> {
         let width = u16::try_from(dimensions.0)?;
-        let height = u16::try_from(dimensions.1)?;
+        let height = dimensions.1;
 
         Ok(Self {
             decoder: fax34::decoder::Group4Decoder::new(

tests/decode_images.rs

@@ -720,3 +720,24 @@ fn extra_bits_gray() {
 fn extra_bits_rgb() {
     test_image_sum_u8("extra_bits_rgb_8b.tiff", ColorType::RGB(8), 0);
 }
+
+
+#[test]
+#[cfg(feature = "fax")]
+fn test_decode_huge_g4() {
+    let path = PathBuf::from(TEST_IMAGE_DIR).join("big_g4.tif");
+    let img_file = File::open(path).expect("failed to open large G4 test image");
+    let mut decoder = tiff::decoder::Decoder::new(img_file).expect("failed to create decoder");
+
+    let (width, height) = decoder.dimensions().expect("failed to get dimensions");
+    
+    assert!(height > u16::MAX as u32, "Test image height {} is not large enough to test u16 overflow", height);
+
+    let result = decoder.read_image().expect("failed to decode huge G4 image");
+
+    if let tiff::decoder::DecodingResult::U8(data) = result {
+        assert_eq!(data.len(), (width as usize * height as usize));
+    } else {
+        panic!("Unexpected decoding result type");
+    }
+}