From 59d32a66a75b11f905ec8c3cd575cedf458200fc Mon Sep 17 00:00:00 2001
From: "A. Molzer" <5550310+197g@users.noreply.github.com>
Date: Mon, 14 Jul 2025 17:49:55 +0200
Subject: [PATCH] Add test coverage for to byte decoding

---
 Cargo.toml             |  2 ++
 src/decoder/mod.rs     |  4 +++
 tests/decode_images.rs | 57 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index ae4f4e3..22d4718 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,6 +27,8 @@ zune-jpeg = { version = "0.4.17", optional = true }
 
 [dev-dependencies]
 criterion = "0.3.1"
+# We may already depend on this via flate2
+crc32fast = "1"
 
 [features]
 default = ["deflate", "jpeg", "lzw"]
diff --git a/src/decoder/mod.rs b/src/decoder/mod.rs
index 780a22c..0587385 100644
--- a/src/decoder/mod.rs
+++ b/src/decoder/mod.rs
@@ -1001,6 +1001,8 @@ impl<R: Read + Seek> Decoder<R> {
     /// Returns the layout without being specific as to the underlying type for forward
     /// compatibility. Note that, in general, a TIFF may contain an almost arbitrary number of
     /// channels of individual *bit* length and format each.
+    ///
+    /// See [`Self::colortype`] to describe the sample types.
     pub fn image_chunk_buffer_layout(&mut self, chunk_index: u32) -> TiffResult<Layout> {
         let data_dims = self.image().chunk_data_dimensions(chunk_index)?;
         self.result_extent(data_dims.0 as usize, data_dims.1 as usize)?
@@ -1052,6 +1054,8 @@ impl<R: Read + Seek> Decoder<R> {
     /// Returns the layout without being specific as to the underlying type for forward
     /// compatibility. Note that, in general, a TIFF may contain an almost arbitrary number of
     /// channels of individual *bit* length and format each.
+    ///
+    /// See [`Self::colortype`] to describe the sample types.
     pub fn image_buffer_layout(&mut self) -> TiffResult<Layout> {
         let width = self.image().width;
         let height = self.image().height;
diff --git a/tests/decode_images.rs b/tests/decode_images.rs
index 5a62279..bc93640 100644
--- a/tests/decode_images.rs
+++ b/tests/decode_images.rs
@@ -522,3 +522,60 @@ fn test_zstd_compression() {
     // gdal_translate -co COMPRESS=ZSTD -co ZSTD_LEVEL=20 int16.tif int16_zstd.tif
     test_image_sum_i16("int16_zstd.tif", ColorType::Gray(16), 354396);
 }
+
+fn test_image_bytes(file: &str, expected: &[(ColorType, u32)]) {
+    let path = PathBuf::from(TEST_IMAGE_DIR).join(file);
+    let img_file = File::open(path).expect("Cannot find test image!");
+    let mut decoder = Decoder::new(img_file).expect("Cannot create decoder");
+
+    let mut buffer = vec![0u8; 0];
+    for (idx, &(expected_type, expected_crc)) in expected.iter().enumerate() {
+        if idx > 0 {
+            decoder
+                .next_image()
+                .expect("mismatched number of directories");
+        }
+
+        assert_eq!(decoder.colortype().unwrap(), expected_type);
+        let layout = decoder
+            .image_buffer_layout()
+            .expect("Cannot describe buffer layout");
+
+        buffer.resize(layout.size(), 0u8);
+        decoder.read_image_bytes(&mut buffer).unwrap();
+
+        // Well almost a crc..
+        assert_eq!(crc32fast::hash(&buffer), expected_crc);
+    }
+}
+
+#[test]
+fn bytes_cmyk_3c_8b() {
+    test_image_bytes("cmyk-3c-8b.tiff", &[(ColorType::CMYK(8), 2935032230)]);
+}
+
+#[test]
+fn bytes_gray_16b() {
+    test_image_bytes(
+        "minisblack-1c-16b.tiff",
+        &[(ColorType::Gray(16), 3524597615)],
+    );
+}
+
+#[test]
+fn bytes_gray_32b() {
+    test_image_bytes("gradient-1c-32b.tiff", &[(ColorType::Gray(32), 2257036530)]);
+}
+
+#[test]
+fn bytes_gray_u64() {
+    test_image_bytes("gradient-1c-64b.tiff", &[(ColorType::Gray(64), 2156547113)]);
+}
+
+#[test]
+fn bytes_gray_f32() {
+    test_image_bytes(
+        "gradient-1c-32b-float.tiff",
+        &[(ColorType::Gray(32), 3232356730)],
+    );
+}