From 5e75642efd6363ba152ccf6a0d3b87840184c324 Mon Sep 17 00:00:00 2001
From: Jyrki Alakuijala <jyrki@google.com>
Date: Thu, 11 Jun 2015 18:49:37 +0000
Subject: [PATCH] lossless: rle mode not to accept lengths smaller than 4.

Gives a compression gain of 0.22 %

Change-Id: I0f3b8dad6b4c1bfb16eab095a467f34466b9e3b7
---
 src/enc/backward_references.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/enc/backward_references.c b/src/enc/backward_references.c
index a6d64d1d..ca9f2675 100644
--- a/src/enc/backward_references.c
+++ b/src/enc/backward_references.c
@@ -368,7 +368,15 @@ static int BackwardReferencesRle(int xsize, int ysize,
     if (argb[i] == argb[i - 1]) {
       ++match_len;
     } else {
-      PushBackCopy(refs, match_len);
+      const int kMinLength = 4;
+      if (match_len >= kMinLength) {
+        PushBackCopy(refs, match_len);
+      } else {
+        int k;
+        for(k = match_len; k >= 1; --k) {
+          AddSingleLiteral(argb[i - k], use_color_cache, &hashers, refs);
+        }
+      }
       match_len = 0;
       AddSingleLiteral(argb[i], use_color_cache, &hashers, refs);
     }