Encoding of extra samples, roundtrip test

tests/decode_images.rs

@@ -686,19 +686,37 @@ fn test_fax4_white_is_min() {
 }
 
 #[test]
-fn extra_bits_image() {
+fn write_extra_bits_image() {
     use tiff::{encoder, tags::ExtraSamples};
 
-    let path = PathBuf::from(TEST_IMAGE_DIR).join("extra_bits_gray_4b.tiff");
+    let path = PathBuf::from(TEST_IMAGE_DIR).join("extra_bits_rgb_8b.tiff");
     let img_file = File::create(path).expect("Cannot find test image!");
 
     let mut encoder = encoder::TiffEncoder::new(img_file).expect("Cannot create encoder");
-    let mut img = encoder
-        .new_image::<encoder::colortype::Gray8>(8, 8)
-        .unwrap();
+    let mut img = encoder.new_image::<encoder::colortype::RGB8>(8, 8).unwrap();
 
     img.extra_samples(&[ExtraSamples::Unspecified]).unwrap();
 
-    let data: [u8; 128] = core::array::from_fn(|i| i as u8 % 2);
-    img.write_data(&data).expect("correct amount of data to write");
+    // all pixels are supposed to be 0, the extra is 1
+    let data: [u8; 256] = core::array::from_fn(|i| (i as u8 % 4).saturating_sub(2));
+
+    img.write_data(&data)
+        .expect("correct amount of data to write");
+}
+
+#[test]
+fn extra_bits_gray() {
+    test_image_sum_u8(
+        "extra_bits_gray_8b.tiff",
+        ColorType::Multiband {
+            bit_depth: 8,
+            num_samples: 2,
+        },
+        64,
+    );
+}
+
+#[test]
+fn extra_bits_rgb() {
+    test_image_sum_u8("extra_bits_rgb_8b.tiff", ColorType::RGB(8), 0);
 }

tests/encode_images.rs

@@ -57,7 +57,7 @@ fn encode_decode() {
                 ),
                 (Tag::Compression, ifd::Value::Short(1)),
                 (Tag::PhotometricInterpretation, ifd::Value::Short(2)),
-                (Tag::StripOffsets, ifd::Value::Unsigned(47)),
+                (Tag::StripOffsets, ifd::Value::Unsigned(35)),
                 (Tag::SamplesPerPixel, ifd::Value::Short(3)),
                 (Tag::RowsPerStrip, ifd::Value::Unsigned(3334)),
                 (Tag::StripByteCounts, ifd::Value::Unsigned(30000)),