/*

 * Copyright 2016 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.

 */

#include "guetzli/jpeg_data_decoder.h"

#include "guetzli/output_image.h"

namespace guetzli {

// Mimic libjpeg's heuristics to guess jpeg color space.

// Requires that the jpg has 3 components.

bool HasYCbCrColorSpace(const JPEGData& jpg) {

  bool has_Adobe_marker = false;

  uint8_t Adobe_transform = 0;

  for (const std::string& app : jpg.app_data) {

    if (static_cast<uint8_t>(app[0]) == 0xe0) {

      return true;

    } else if (static_cast<uint8_t>(app[0]) == 0xee && app.size() >= 15) {

      has_Adobe_marker = true;

      Adobe_transform = app[14];

    }

  }

  if (has_Adobe_marker) {

    return (Adobe_transform != 0);

  }

  const int cid0 = jpg.components[0].id;

  const int cid1 = jpg.components[1].id;

  const int cid2 = jpg.components[2].id;

  return (cid0 != 'R' || cid1 != 'G' || cid2 != 'B');

}

std::vector<uint8_t> DecodeJpegToRGB(const JPEGData& jpg) {

  if (jpg.components.size() == 1 ||

      (jpg.components.size() == 3 &&

       HasYCbCrColorSpace(jpg) && (jpg.Is420() || jpg.Is444()))) {

    OutputImage img(jpg.width, jpg.height);

    img.CopyFromJpegData(jpg);

    return img.ToSRGB();

  }

  return std::vector<uint8_t>();

}

}  // namespace guetzli