/*

* 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 "jpeg_data_decoder.h"

#include "output_image.h"

namespace knusperli {

// 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 knusperli