[ntp4] Use highest quality jpeg compression for thumbnail images.

chrome/browser/history/thumbnail_database.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/history/thumbnail_database.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 24 matching lines @@
       static_cast<history::IconType>(statement.ColumnInt(2));
   icon_mapping->page_url = page_url;
 }
 
 namespace history {
 
 // Version number of the database.
 static const int kCurrentVersionNumber = 5;
 static const int kCompatibleVersionNumber = 5;
 
+// Use 90 quality (out of 100) which is pretty high, because we're very
+// sensitive to artifacts for these small sized, highly detailed images.
+static const int kImageQuality = 90;
+
 ThumbnailDatabase::ThumbnailDatabase()
     : history_publisher_(NULL),
       use_top_sites_(false) {
 }
 
 sql::InitStatus ThumbnailDatabase::CantUpgradeToVersion(int cur_version) {
   LOG(WARNING) << "Unable to update to thumbnail database to version 4" <<
                cur_version << ".";
   db_.Close();
   return sql::INIT_FAILURE;
@@ skipping 200 matching lines @@
 
     if (add_thumbnail) {
       sql::Statement statement(db_.GetCachedStatement(SQL_FROM_HERE,
           "INSERT OR REPLACE INTO thumbnails "
           "(url_id, boring_score, good_clipping, at_top, last_updated, data) "
           "VALUES (?,?,?,?,?,?)"));
       if (!statement)
         return;
 
       std::vector<unsigned char> jpeg_data;
-      bool encoded = gfx::JPEGEncodedDataFromImage(*thumbnail, &jpeg_data);
+      bool encoded = gfx::JPEGEncodedDataFromImage(*thumbnail, kImageQuality,
+                                                   &jpeg_data);
       if (encoded) {
         statement.BindInt64(0, id);
         statement.BindDouble(1, score.boring_score);
         statement.BindBool(2, score.good_clipping);
         statement.BindBool(3, score.at_top);
         statement.BindInt64(4, score.time_at_snapshot.ToTimeT());
         statement.BindBlob(5, &jpeg_data[0],
                            static_cast<int>(jpeg_data.size()));
         if (!statement.Run())
           NOTREACHED() << db_.GetErrorMessage();
@@ skipping 503 matching lines @@
   if (!db_.Execute("ALTER TABLE favicons ADD sizes LONGVARCHAR")) {
     NOTREACHED();
     return false;
   }
   meta_table_.SetVersionNumber(5);
   meta_table_.SetCompatibleVersionNumber(std::min(5, kCompatibleVersionNumber));
   return true;
 }
 
 }  // namespace history