Fix more issues with alpha optim on interlaced images

Closes #133

CHANGELOG.md

@@ -1,3 +1,6 @@
+### Version 2.1.1
+ - More fixes for alpha optimization on interlaced images ([#133](https://github.com/shssoichiro/oxipng/issues/133))
+
 ### Version 2.1.0
  - [SEMVER_MINOR] Bump minimum Rust version to 1.27.0
  - [SEMVER_MINOR] Reenable faster Cloudflare zlib compression on platforms that support it

src/png/mod.rs

@@ -712,9 +712,12 @@ impl PngData {
         let mut lines = Vec::new();
         let mut scan_lines = self.scan_lines().collect::<Vec<ScanLine>>();
         scan_lines.reverse();
-        let mut last_line = vec![0; scan_lines[0].data.len()];
+        let mut last_line = Vec::new();
         let mut current_line = Vec::with_capacity(last_line.len());
         for line in scan_lines {
+            if line.data.len() != last_line.len() {
+                last_line = vec![0; line.data.len()];
+            }
             current_line.push(line.filter);
             for (pixel, last_pixel) in line.data.chunks(bpp).zip(last_line.chunks(bpp)) {
                 if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {
@@ -735,8 +738,11 @@ impl PngData {
 
     fn reduce_alpha_to_down(&self, bpc: usize, bpp: usize) -> Vec<u8> {
         let mut reduced = Vec::with_capacity(self.raw_data.len());
-        let mut last_line = vec![0; self.scan_lines().next().unwrap().data.len()];
+        let mut last_line = Vec::new();
         for line in self.scan_lines() {
+            if line.data.len() != last_line.len() {
+                last_line = vec![0; line.data.len()];
+            }
             reduced.push(line.filter);
             for (pixel, last_pixel) in line.data.chunks(bpp).zip(last_line.chunks(bpp)) {
                 if pixel.iter().skip(bpp - bpc).fold(0, |sum, i| sum | i) == 0 {

tests/regression.rs

@@ -291,14 +291,14 @@ fn issue_92_filter_5() {
 }
 
 #[test]
-fn issue_113() {
+fn issue_113_white() {
     let input = "tests/files/issue-113.png";
     let (_, mut opts) = get_opts(Path::new(input));
     opts.interlace = Some(1);
     opts.alphas = HashSet::new();
-    opts.alphas.insert(AlphaOptim::Up);
+    opts.alphas.insert(AlphaOptim::Black);
     let output = OutFile::Path(Some(
-        Path::new(input).with_extension("-f5-out.png").to_owned(),
+        Path::new(input).with_extension("-white-out.png").to_owned(),
     ));
     test_it_converts(
         input,
@@ -309,3 +309,217 @@ fn issue_113() {
         BitDepth::Eight,
     );
 }
+
+#[test]
+fn issue_113_black() {
+    let input = "tests/files/issue-113.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.interlace = Some(1);
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Black);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-black-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_113_right() {
+    let input = "tests/files/issue-113.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.interlace = Some(1);
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Right);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-right-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_113_left() {
+    let input = "tests/files/issue-113.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.interlace = Some(1);
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Left);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-left-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_113_up() {
+    let input = "tests/files/issue-113.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.interlace = Some(1);
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Up);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-up-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_113_down() {
+    let input = "tests/files/issue-113.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.interlace = Some(1);
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Down);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-down-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::GrayscaleAlpha,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_133_black() {
+    let input = "tests/files/issue-133.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Black);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-black-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGBA,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_133_white() {
+    let input = "tests/files/issue-133.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::White);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-white-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGBA,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_133_up() {
+    let input = "tests/files/issue-133.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Up);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-up-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGBA,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_133_down() {
+    let input = "tests/files/issue-133.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Down);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-down-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGBA,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_133_right() {
+    let input = "tests/files/issue-133.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Right);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-right-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGBA,
+        BitDepth::Eight,
+    );
+}
+
+#[test]
+fn issue_133_left() {
+    let input = "tests/files/issue-133.png";
+    let (_, mut opts) = get_opts(Path::new(input));
+    opts.alphas = HashSet::new();
+    opts.alphas.insert(AlphaOptim::Left);
+    let output = OutFile::Path(Some(
+        Path::new(input).with_extension("-left-out.png").to_owned(),
+    ));
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::RGBA,
+        BitDepth::Eight,
+        ColorType::RGBA,
+        BitDepth::Eight,
+    );
+}