From c8f9c84d5e12b69b8c3c96bbf86af3bb1cf2f998 Mon Sep 17 00:00:00 2001
From: Urvang Joshi <urvang@google.com>
Date: Sun, 16 Jun 2013 02:00:44 -0700
Subject: [PATCH] Regression fix for alpha unfiltering:

For vertical filter, correctly initialize 'preds' when not starting at
row 0.

Change-Id: I69697d73dde8a2f701f376ff3986d09fa6f7fee3
---
 src/utils/filters.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/utils/filters.c b/src/utils/filters.c
index 40254145..511457ec 100644
--- a/src/utils/filters.c
+++ b/src/utils/filters.c
@@ -112,6 +112,9 @@ static WEBP_INLINE void DoVerticalFilter(const uint8_t* in,
     row = 1;
     in += stride;
     out += stride;
+  } else {
+    // We are starting from in-between. Make sure 'preds' points to prev row.
+    preds -= stride;
   }
 
   // Filter line-by-line.