From 97934e2447499face1e3dedb33e44d69a2fd04a1 Mon Sep 17 00:00:00 2001
From: Pascal Massimino <pascal.massimino@gmail.com>
Date: Fri, 18 Mar 2016 11:01:54 +0100
Subject: [PATCH] Revert "Re-enable encoding of alpha plane with color cache
 for next release."

This avoids generating file that would trigger a decoding bug
found in 0.4.0 -> 0.4.3 libwebp versions.

This reverts commit 6ecd72f845d0c3604f2cccd2b31dc650627d3b2f.

Change-Id: I4667cc8f7b851ba44479e3fe2b9d844b2c56fcf4
---
 src/enc/alpha.c |  6 +++++-
 src/enc/vp8l.c  | 13 +++++++------
 src/enc/vp8li.h |  3 ++-
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/enc/alpha.c b/src/enc/alpha.c
index 3c970b00..2ad3298b 100644
--- a/src/enc/alpha.c
+++ b/src/enc/alpha.c
@@ -79,7 +79,11 @@ static int EncodeLossless(const uint8_t* const data, int width, int height,
   config.quality = 8.f * effort_level;
   assert(config.quality >= 0 && config.quality <= 100.f);
 
-  ok = (VP8LEncodeStream(&config, &picture, bw) == VP8_ENC_OK);
+  // TODO(urvang): Temporary fix to avoid generating images that trigger
+  // a decoder bug related to alpha with color cache.
+  // See: https://code.google.com/p/webp/issues/detail?id=239
+  // Need to re-enable this later.
+  ok = (VP8LEncodeStream(&config, &picture, bw, 0 /*use_cache*/) == VP8_ENC_OK);
   WebPPictureFree(&picture);
   ok = ok && !bw->error_;
   if (!ok) {
diff --git a/src/enc/vp8l.c b/src/enc/vp8l.c
index e77581c6..2c308577 100644
--- a/src/enc/vp8l.c
+++ b/src/enc/vp8l.c
@@ -824,7 +824,8 @@ static WebPEncodingError EncodeImageInternal(VP8LBitWriter* const bw,
                                              VP8LHashChain* const hash_chain,
                                              VP8LBackwardRefs refs_array[2],
                                              int width, int height, int quality,
-                                             int low_effort, int* cache_bits,
+                                             int low_effort,
+                                             int use_cache, int* cache_bits,
                                              int histogram_bits,
                                              size_t init_byte_position,
                                              int* const hdr_size,
@@ -856,7 +857,7 @@ static WebPEncodingError EncodeImageInternal(VP8LBitWriter* const bw,
     goto Error;
   }
 
-  *cache_bits = MAX_COLOR_CACHE_BITS;
+  *cache_bits = use_cache ? MAX_COLOR_CACHE_BITS : 0;
   // 'best_refs' is the reference to the best backward refs and points to one
   // of refs_array[0] or refs_array[1].
   // Calculate backward references from ARGB image.
@@ -1384,7 +1385,7 @@ static void VP8LEncoderDelete(VP8LEncoder* enc) {
 
 WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
                                    const WebPPicture* const picture,
-                                   VP8LBitWriter* const bw) {
+                                   VP8LBitWriter* const bw, int use_cache) {
   WebPEncodingError err = VP8_ENC_OK;
   const int quality = (int)config->quality;
   const int low_effort = (config->method == 0);
@@ -1480,8 +1481,8 @@ WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
   // Encode and write the transformed image.
   err = EncodeImageInternal(bw, enc->argb_, &enc->hash_chain_, enc->refs_,
                             enc->current_width_, height, quality, low_effort,
-                            &enc->cache_bits_, enc->histo_bits_, byte_position,
-                            &hdr_size, &data_size);
+                            use_cache, &enc->cache_bits_, enc->histo_bits_,
+                            byte_position, &hdr_size, &data_size);
   if (err != VP8_ENC_OK) goto Error;
 
   if (picture->stats != NULL) {
@@ -1566,7 +1567,7 @@ int VP8LEncodeImage(const WebPConfig* const config,
   if (!WebPReportProgress(picture, 5, &percent)) goto UserAbort;
 
   // Encode main image stream.
-  err = VP8LEncodeStream(config, picture, &bw);
+  err = VP8LEncodeStream(config, picture, &bw, 1 /*use_cache*/);
   if (err != VP8_ENC_OK) goto Error;
 
   // TODO(skal): have a fine-grained progress report in VP8LEncodeStream().
diff --git a/src/enc/vp8li.h b/src/enc/vp8li.h
index 6e2721d2..371e276e 100644
--- a/src/enc/vp8li.h
+++ b/src/enc/vp8li.h
@@ -67,9 +67,10 @@ int VP8LEncodeImage(const WebPConfig* const config,
                     const WebPPicture* const picture);
 
 // Encodes the main image stream using the supplied bit writer.
+// If 'use_cache' is false, disables the use of color cache.
 WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
                                    const WebPPicture* const picture,
-                                   VP8LBitWriter* const bw);
+                                   VP8LBitWriter* const bw, int use_cache);
 
 //------------------------------------------------------------------------------