Update libwebp to 0.4.0

third_party/libwebp/enc/config.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.
 // -----------------------------------------------------------------------------
 //
 // Coding tools configuration
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include "../webp/encode.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
-extern "C" {
-#endif
-
 //------------------------------------------------------------------------------
 // WebPConfig
 //------------------------------------------------------------------------------
 
 int WebPConfigInitInternal(WebPConfig* config,
                            WebPPreset preset, float quality, int version) {
   if (WEBP_ABI_IS_INCOMPATIBLE(version, WEBP_ENCODER_ABI_VERSION)) {
     return 0;   // caller/system version mismatch!
   }
   if (config == NULL) return 0;
 
   config->quality = quality;
   config->target_size = 0;
   config->target_PSNR = 0.;
   config->method = 4;
   config->sns_strength = 50;
-  config->filter_strength = 60;   // rather high filtering, helps w/ gradients.
+  config->filter_strength = 60;   // mid-filtering
   config->filter_sharpness = 0;
   config->filter_type = 1;        // default: strong (so U/V is filtered too)
   config->partitions = 0;
   config->segments = 4;
   config->pass = 1;
   config->show_compressed = 0;
   config->preprocessing = 0;
   config->autofilter = 0;
   config->partition_limit = 0;
   config->alpha_compression = 1;
   config->alpha_filtering = 1;
   config->alpha_quality = 100;
   config->lossless = 0;
   config->image_hint = WEBP_HINT_DEFAULT;
   config->emulate_jpeg_size = 0;
   config->thread_level = 0;
   config->low_memory = 0;
 
   // TODO(skal): tune.
   switch (preset) {
     case WEBP_PRESET_PICTURE:
       config->sns_strength = 80;
       config->filter_sharpness = 4;
       config->filter_strength = 35;
+      config->preprocessing &= ~2;   // no dithering
       break;
     case WEBP_PRESET_PHOTO:
       config->sns_strength = 80;
       config->filter_sharpness = 3;
       config->filter_strength = 30;
+      config->preprocessing |= 2;
       break;
     case WEBP_PRESET_DRAWING:
       config->sns_strength = 25;
       config->filter_sharpness = 6;
       config->filter_strength = 10;
       break;
     case WEBP_PRESET_ICON:
       config->sns_strength = 0;
       config->filter_strength = 0;   // disable filtering to retain sharpness
+      config->preprocessing &= ~2;   // no dithering
       break;
     case WEBP_PRESET_TEXT:
       config->sns_strength = 0;
       config->filter_strength = 0;   // disable filtering to retain sharpness
+      config->preprocessing &= ~2;   // no dithering
       config->segments = 2;
       break;
     case WEBP_PRESET_DEFAULT:
     default:
       break;
   }
   return WebPValidateConfig(config);
 }
 
 int WebPValidateConfig(const WebPConfig* config) {
@@ skipping 15 matching lines @@
   if (config->filter_sharpness < 0 || config->filter_sharpness > 7)
     return 0;
   if (config->filter_type < 0 || config->filter_type > 1)
     return 0;
   if (config->autofilter < 0 || config->autofilter > 1)
     return 0;
   if (config->pass < 1 || config->pass > 10)
     return 0;
   if (config->show_compressed < 0 || config->show_compressed > 1)
     return 0;
-  if (config->preprocessing < 0 || config->preprocessing > 1)
+  if (config->preprocessing < 0 || config->preprocessing > 3)
     return 0;
   if (config->partitions < 0 || config->partitions > 3)
     return 0;
   if (config->partition_limit < 0 || config->partition_limit > 100)
     return 0;
   if (config->alpha_compression < 0)
     return 0;
   if (config->alpha_filtering < 0)
     return 0;
   if (config->alpha_quality < 0 || config->alpha_quality > 100)
     return 0;
   if (config->lossless < 0 || config->lossless > 1)
     return 0;
   if (config->image_hint >= WEBP_HINT_LAST)
     return 0;
   if (config->emulate_jpeg_size < 0 || config->emulate_jpeg_size > 1)
     return 0;
   if (config->thread_level < 0 || config->thread_level > 1)
     return 0;
   if (config->low_memory < 0 || config->low_memory > 1)
     return 0;
   return 1;
 }
 
 //------------------------------------------------------------------------------
 
-#if defined(__cplusplus) || defined(c_plusplus)
-}    // extern "C"
-#endif