include/cros-camera/jpeg_compressor.h

/*
 * Copyright 2017 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef INCLUDE_CROS_CAMERA_JPEG_COMPRESSOR_H_
#define INCLUDE_CROS_CAMERA_JPEG_COMPRESSOR_H_

// We must include cstdio before jpeglib.h. It is a requirement of libjpeg.
#include <cstdio>
#include <string>
#include <vector>

extern "C" {
#include <jerror.h>
#include <jpeglib.h>
}

#include "cros-camera/export.h"

namespace cros {

// Encapsulates a converter from YU12 to JPEG format. This class is not
// thread-safe.
class CROS_CAMERA_EXPORT JpegCompressor {
 public:
  JpegCompressor();
  ~JpegCompressor();

  // Compresses YU12 image to JPEG format. |quality| is the resulted jpeg
  // image quality. It ranges from 1 (poorest quality) to 100 (highest quality).
  // |app1_buffer| is the buffer of APP1 segment (exif) which will be added to
  // the compressed image. Caller should pass the size of output buffer to
  // |out_buffer_size|. Encoded result will be written into |output_buffer|.
  // The actually encoded size will be written into |out_data_size| if image
  // encoded successfully. Returns false if errors occur during compression.
  bool CompressImage(const void* image,
                     int width,
                     int height,
                     int quality,
                     const void* app1_buffer,
                     uint32_t app1_size,
                     uint32_t out_buffer_size,
                     void* out_buffer,
                     uint32_t* out_data_size);

  // Compresses YU12 image to JPEG format. |quality| is the resulted jpeg
  // image quality. It ranges from 1 (poorest quality) to 100 (highest quality).
  // Caller should pass the size of output buffer to |out_buffer_size|. Encoded
  // result will be written into |output_buffer|. The actually encoded size will
  // be written into |out_data_size| if image encoded successfully. Returns
  // false if errors occur during compression.
  bool GenerateThumbnail(const void* image,
                         int image_width,
                         int image_height,
                         int thumbnail_width,
                         int thumbnail_height,
                         int quality,
                         uint32_t out_buffer_size,
                         void* out_buffer,
                         uint32_t* out_data_size);

 private:
  // InitDestination(), EmptyOutputBuffer() and TerminateDestination() are
  // callback functions to be passed into jpeg library.
  static void InitDestination(j_compress_ptr cinfo);
  static boolean EmptyOutputBuffer(j_compress_ptr cinfo);
  static void TerminateDestination(j_compress_ptr cinfo);
  static void OutputErrorMessage(j_common_ptr cinfo);

  // Returns false if errors occur.
  bool Encode(const void* inYuv,
              int width,
              int height,
              int jpegQuality,
              const void* app1_buffer,
              unsigned int app1_size,
              uint32_t out_buffer_size,
              void* out_buffer,
              uint32_t* out_data_size);
  void SetJpegDestination(jpeg_compress_struct* cinfo);
  void SetJpegCompressStruct(int width,
                             int height,
                             int quality,
                             jpeg_compress_struct* cinfo);
  // Returns false if errors occur.
  bool Compress(jpeg_compress_struct* cinfo, const uint8_t* yuv);

  // Process 16 lines of Y and 16 lines of U/V each time.
  // We must pass at least 16 scanlines according to libjpeg documentation.
  static const int kCompressBatchSize = 16;

  // Point to output buffer. JpegCompressor doesn't own this buffer.
  JOCTET* out_buffer_ptr_;

  // Output buffer size.
  uint32_t out_buffer_size_;

  // Final JPEG encoded size.
  uint32_t out_data_size_;

  // Since output buffer is passed from caller, use a variable to indicate
  // buffer is enough to encode or not.
  bool is_encode_success_;
};

}  // namespace cros

#endif  // INCLUDE_CROS_CAMERA_JPEG_COMPRESSOR_H_