From 11f3a6e7a2ca69fbf317bc69173bbf59f1dfb8f8 Mon Sep 17 00:00:00 2001
From: Gunnsteinn Hall <gunnsteinn.hall@gmail.com>
Date: Thu, 16 Apr 2020 23:05:50 +0000
Subject: [PATCH] Fix for crash in CCITT decoder.  Resolves
 https://github.com/unidoc/unipdf/issues/314 (#315)

---
 internal/ccittfax/encoder.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/internal/ccittfax/encoder.go b/internal/ccittfax/encoder.go
index a8ac5e5e..97cf2daf 100644
--- a/internal/ccittfax/encoder.go
+++ b/internal/ccittfax/encoder.go
@@ -412,6 +412,11 @@ func seekChangingElem(row []byte, currElem int) int {
 	if currElem >= len(row) {
 		return currElem
 	}
+	if currElem < -1 {
+		// A current element of -1 means white color starting prior to first element (0).
+		// Should not be able to go any further left than that.
+		currElem = -1
+	}
 
 	var color byte
 	if currElem > -1 {