From 493853031b4ad6d372c36555819afa7d3ebdbb23 Mon Sep 17 00:00:00 2001
From: jazzchipc <josealeixo.pc@outlook.com>
Date: Sun, 4 Dec 2016 19:44:12 +0000
Subject: [PATCH] Fixes issue #6071.

Corrects readBlockTiff() case for 1-bit depth and 1 color TIFF images incorporated in the PDF.

Adds reference test for PDF used to fix this issue.
---
 src/core/stream.js           | 17 +++++++++--------
 test/pdfs/issue6071.pdf.link |  1 +
 test/test_manifest.json      |  7 +++++++
 3 files changed, 17 insertions(+), 8 deletions(-)
 create mode 100644 test/pdfs/issue6071.pdf.link

diff --git a/src/core/stream.js b/src/core/stream.js
index 9d8f14850..a7da21c1e 100644
--- a/src/core/stream.js
+++ b/src/core/stream.js
@@ -739,15 +739,16 @@ var PredictorStream = (function PredictorStreamClosure() {
     var pos = bufferLength;
     var i;
 
-    if (bits === 1) {
+    if (bits === 1 && colors === 1) {
+      // Optimized version of the loop in the "else"-branch
+      // for 1 bit-per-component and 1 color TIFF images.
       for (i = 0; i < rowBytes; ++i) {
-        var c = rawBytes[i];
-        inbuf = (inbuf << 8) | c;
-        // bitwise addition is exclusive or
-        // first shift inbuf and then add
-        buffer[pos++] = (c ^ (inbuf >> colors)) & 0xFF;
-        // truncate inbuf (assumes colors < 16)
-        inbuf &= 0xFFFF;
+        var c = rawBytes[i] ^ inbuf;
+        c ^= c >> 1;
+        c ^= c >> 2;
+        c ^= c >> 4;
+        inbuf = (c & 1) << 7;
+        buffer[pos++] = c;
       }
     } else if (bits === 8) {
       for (i = 0; i < colors; ++i) {
diff --git a/test/pdfs/issue6071.pdf.link b/test/pdfs/issue6071.pdf.link
new file mode 100644
index 000000000..2e2cd690c
--- /dev/null
+++ b/test/pdfs/issue6071.pdf.link
@@ -0,0 +1 @@
+https://web.archive.org/web/20170107214304/https://www.pdf-archive.com/2017/01/07/issue6071/issue6071.pdf
\ No newline at end of file
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 5d669044e..55c4e0c24 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -1146,6 +1146,13 @@
        "lastPage": 2,
        "type": "eq"
     },
+    {  "id": "issue6071",
+       "file": "pdfs/issue6071.pdf",
+       "md5": "2e08526d8e7c9ba4269fc12ef488d3eb",
+       "rounds": 1,
+       "link": true,
+       "type": "eq"
+    },
     {  "id": "issue1905",
        "file": "pdfs/issue1905.pdf",
        "md5": "b1bbd72ca6522ae1502aa26320f81994",