From 4adcc5e14ac4c7ff6905ba9cc91890e4ac667579 Mon Sep 17 00:00:00 2001
From: Felix Hanau <felix@cloudflare.com>
Date: Wed, 24 Jul 2019 14:16:13 +0100
Subject: [PATCH] Interlacing fixes (#182)

* Fix decoding interlaced images with height or width <= 2

* Add Issue 175 test case

* Deinterlace tiny images correctly
---
 src/interlace.rs    | 13 +++++++++++++
 tests/regression.rs | 18 +++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/interlace.rs b/src/interlace.rs
index 5f2daccf..2d391934 100644
--- a/src/interlace.rs
+++ b/src/interlace.rs
@@ -135,6 +135,19 @@ pub fn deinterlace_image(png: &PngImage) -> PngImage {
             if current_pass == 3 && png.ihdr.height <= 4 {
                 current_pass += 1;
             }
+            if current_pass == 4 && png.ihdr.width <= 2 {
+                current_pass += 1;
+            }
+            if current_pass == 5 && png.ihdr.height <= 2 {
+                current_pass += 1;
+            }
+            if current_pass == 6 && png.ihdr.width == 1 {
+                current_pass += 1;
+            }
+            if current_pass == 7 && png.ihdr.height == 1 {
+                break;
+            }
+
             pass_constants = interlaced_constants(current_pass);
             current_y = pass_constants.y_shift as usize;
         }
diff --git a/tests/regression.rs b/tests/regression.rs
index a5d8bd39..867902ab 100644
--- a/tests/regression.rs
+++ b/tests/regression.rs
@@ -634,4 +634,20 @@ fn issue_175() {
         ColorType::Grayscale,
         BitDepth::One,
     );
-}
\ No newline at end of file
+}
+
+#[test]
+fn issue_182() {
+    let input = "tests/files/issue-175.png";
+    let (output, mut opts) = get_opts(Path::new(input));
+    opts.interlace = Some(0);
+
+    test_it_converts(
+        input,
+        Some((output, opts)),
+        ColorType::Grayscale,
+        BitDepth::One,
+        ColorType::Grayscale,
+        BitDepth::One,
+    );
+}