src/pagespeed/kernel/image/jpeg_utils.h

/*
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Author: Satyanarayana Manyam

#ifndef PAGESPEED_KERNEL_IMAGE_JPEG_UTILS_H_
#define PAGESPEED_KERNEL_IMAGE_JPEG_UTILS_H_

#include <cstddef>
#include "pagespeed/kernel/base/basictypes.h"

namespace net_instaweb {
class MessageHandler;
}

namespace pagespeed {

namespace image_compression {

using net_instaweb::MessageHandler;

// Utility class that reads jpeg parameter from jpeg images.
class JpegUtils {
 public:
  // Get image quality with which the input jpeg image is compressed. This
  // method will return -1 if it is not able to either jpeg image is invalid or
  // image quality can't be determined.
  //
  // See comments in implementation for additional details on how quality is
  // computed.
  static int GetImageQualityFromImage(const void* image_data,
                                      size_t image_length,
                                      MessageHandler* handler);

 private:
  JpegUtils();
  DISALLOW_COPY_AND_ASSIGN(JpegUtils);
};

}  // namespace image_compression

}  // namespace pagespeed

#endif  // PAGESPEED_KERNEL_IMAGE_JPEG_UTILS_H_