libwebp: update to v0.5.1

third_party/libwebp/enc/alpha.c

 // Copyright 2011 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS. All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 // -----------------------------------------------------------------------------
 //
 // Alpha-plane compression.
@@ skipping 61 matching lines @@
   // internal encoding-related image containing necessary exact information in
   // RGB channels.
   config.exact = 1;
   config.method = effort_level;  // impact is very small
   // Set a low default quality for encoding alpha. Ensure that Alpha quality at
   // lower methods (3 and below) is less than the threshold for triggering
   // costly 'BackwardReferencesTraceBackwards'.
   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) {
     VP8LBitWriterWipeOut(bw);
     return 0;
   }
   return 1;
 }
 
 // -----------------------------------------------------------------------------
@@ skipping 18 matching lines @@
   const size_t data_size = width * height;
   const uint8_t* output = NULL;
   size_t output_size = 0;
   VP8LBitWriter tmp_bw;
 
   assert((uint64_t)data_size == (uint64_t)width * height);  // as per spec
   assert(filter >= 0 && filter < WEBP_FILTER_LAST);
   assert(method >= ALPHA_NO_COMPRESSION);
   assert(method <= ALPHA_LOSSLESS_COMPRESSION);
   assert(sizeof(header) == ALPHA_HEADER_LEN);
-  // TODO(skal): have a common function and #define's to validate alpha params.
 
   filter_func = WebPFilters[filter];
   if (filter_func != NULL) {
     filter_func(data, width, height, width, tmp_alpha);
     alpha_src = tmp_alpha;
   }  else {
     alpha_src = data;
   }
 
   if (method != ALPHA_NO_COMPRESSION) {
@@ skipping 289 matching lines @@
     ok = WebPGetWorkerInterface()->Sync(worker);
     // still need to end the worker, even if !ok
     WebPGetWorkerInterface()->End(worker);
   }
   WebPSafeFree(enc->alpha_data_);
   enc->alpha_data_ = NULL;
   enc->alpha_data_size_ = 0;
   enc->has_alpha_ = 0;
   return ok;
 }