Add grayscale depth tests and benches

benches/reductions.rs

@@ -75,6 +75,66 @@ fn reductions_2_to_1_bits(b: &mut Bencher) {
     b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
 }
 
+#[bench]
+fn reductions_grayscale_8_to_4_bits(b: &mut Bencher) {
+    let input = test::black_box(PathBuf::from(
+        "tests/files/grayscale_8_should_be_grayscale_4.png",
+    ));
+    let png = PngData::new(&input, false).unwrap();
+
+    b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
+}
+
+#[bench]
+fn reductions_grayscale_8_to_2_bits(b: &mut Bencher) {
+    let input = test::black_box(PathBuf::from(
+        "tests/files/grayscale_8_should_be_grayscale_2.png",
+    ));
+    let png = PngData::new(&input, false).unwrap();
+
+    b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
+}
+
+#[bench]
+fn reductions_grayscale_8_to_1_bits(b: &mut Bencher) {
+    let input = test::black_box(PathBuf::from(
+        "tests/files/grayscale_8_should_be_grayscale_1.png",
+    ));
+    let png = PngData::new(&input, false).unwrap();
+
+    b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
+}
+
+#[bench]
+fn reductions_grayscale_4_to_2_bits(b: &mut Bencher) {
+    let input = test::black_box(PathBuf::from(
+        "tests/files/grayscale_4_should_be_grayscale_2.png",
+    ));
+    let png = PngData::new(&input, false).unwrap();
+
+    b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
+}
+
+#[bench]
+fn reductions_grayscale_4_to_1_bits(b: &mut Bencher) {
+    let input = test::black_box(PathBuf::from(
+        "tests/files/grayscale_4_should_be_grayscale_1.png",
+    ));
+    let png = PngData::new(&input, false).unwrap();
+
+    b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
+}
+
+#[bench]
+fn reductions_grayscale_2_to_1_bits(b: &mut Bencher) {
+    let input = test::black_box(PathBuf::from(
+        "tests/files/grayscale_2_should_be_grayscale_1.png",
+    ));
+    let png = PngData::new(&input, false).unwrap();
+
+    b.iter(|| bit_depth::reduce_bit_depth(&png.raw, 1));
+}
+
 #[bench]
 fn reductions_rgba_to_rgb_16(b: &mut Bencher) {
     let input = test::black_box(PathBuf::from("tests/files/rgba_16_should_be_rgb_16.png"));

tests/reduction.rs

@@ -718,6 +718,78 @@ fn grayscale_8_should_be_grayscale_8() {
     );
 }
 
+#[test]
+fn grayscale_8_should_be_grayscale_4() {
+    test_it_converts(
+        "tests/files/grayscale_8_should_be_grayscale_4.png",
+        false,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::Four,
+    );
+}
+
+#[test]
+fn grayscale_8_should_be_grayscale_2() {
+    test_it_converts(
+        "tests/files/grayscale_8_should_be_grayscale_2.png",
+        false,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::Two,
+    );
+}
+
+#[test]
+fn grayscale_4_should_be_grayscale_2() {
+    test_it_converts(
+        "tests/files/grayscale_4_should_be_grayscale_2.png",
+        false,
+        ColorType::Grayscale,
+        BitDepth::Four,
+        ColorType::Grayscale,
+        BitDepth::Two,
+    );
+}
+
+#[test]
+fn grayscale_8_should_be_grayscale_1() {
+    test_it_converts(
+        "tests/files/grayscale_8_should_be_grayscale_1.png",
+        false,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::One,
+    );
+}
+
+#[test]
+fn grayscale_4_should_be_grayscale_1() {
+    test_it_converts(
+        "tests/files/grayscale_4_should_be_grayscale_1.png",
+        false,
+        ColorType::Grayscale,
+        BitDepth::Four,
+        ColorType::Grayscale,
+        BitDepth::One,
+    );
+}
+
+#[test]
+fn grayscale_2_should_be_grayscale_1() {
+    test_it_converts(
+        "tests/files/grayscale_2_should_be_grayscale_1.png",
+        false,
+        ColorType::Grayscale,
+        BitDepth::Two,
+        ColorType::Grayscale,
+        BitDepth::One,
+    );
+}
+
 #[test]
 fn grayscale_alpha_16_should_be_grayscale_trns_16() {
     test_it_converts(