Method Encode

src/core/codecs/jpeg/JpegCodec.cpp:313–366

#ifdef TGFX_USE_JPEG_ENCODE
std::shared_ptr<Data> JpegCodec::Encode(const Pixmap& pixmap, int quality) {
  auto srcPixels = static_cast<uint8_t*>(const_cast<void*>(pixmap.pixels()));
  int srcRowBytes = static_cast<int>(pixmap.rowBytes());
  jpeg_compress_struct cinfo = {};
  jpeg_error_mgr jerr = {};
  JSAMPROW row_pointer[1];
  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_compress(&cinfo);
  uint8_t* dstBuffer = nullptr;
  unsigned long dstBufferSize = 0;  // NOLINT
  jpeg_mem_dest(&cinfo, &dstBuffer, &dstBufferSize);
  cinfo.image_width = static_cast<JDIMENSION>(pixmap.width());
  cinfo.image_height = static_cast<JDIMENSION>(pixmap.height());
  Buffer buffer = {};
  switch (pixmap.colorType()) {
    case ColorType::RGBA_8888:
      cinfo.in_color_space = JCS_EXT_RGBA;
      cinfo.input_components = 4;
      break;
    case ColorType::BGRA_8888:
      cinfo.in_color_space = JCS_EXT_BGRA;
      cinfo.input_components = 4;
      break;
    case ColorType::Gray_8:
      cinfo.in_color_space = JCS_GRAYSCALE;
      cinfo.input_components = 1;
      break;
    default:
      auto info = ImageInfo::Make(pixmap.width(), pixmap.height(), ColorType::RGBA_8888);
      buffer.alloc(info.byteSize());
      if (buffer.isEmpty()) {
        return nullptr;
      }
      srcPixels = buffer.bytes();
      srcRowBytes = static_cast<int>(info.rowBytes());
      Pixmap(info, srcPixels).writePixels(pixmap.info(), pixmap.pixels());
      cinfo.in_color_space = JCS_EXT_RGBA;
      cinfo.input_components = 4;
      break;
  }
  jpeg_set_defaults(&cinfo);
  cinfo.optimize_coding = TRUE;
  jpeg_set_quality(&cinfo, quality, TRUE);
  jpeg_start_compress(&cinfo, TRUE);
  while (cinfo.next_scanline < cinfo.image_height) {
    row_pointer[0] = &(srcPixels)[cinfo.next_scanline * static_cast<JDIMENSION>(srcRowBytes)];
    (void)jpeg_write_scanlines(&cinfo, row_pointer, 1);
  }

  /* similar to read file, clean up after we're done compressing */
  jpeg_finish_compress(&cinfo);
  jpeg_destroy_compress(&cinfo);
  return Data::MakeAdopted(dstBuffer, dstBufferSize, Data::FreeProc);
}
#endif

}  // namespace tgfx