Method process

extensions/usb-camera/GetUSBCamera.cpp:400–457

}

int64_t GetUSBCamera::PNGWriteCallback::process(const std::shared_ptr<io::BaseStream>& stream) {
  std::lock_guard<std::mutex> lock(*png_write_mtx_);
  logger_->log_info("Writing %d bytes of raw capture data to PNG output", frame_->data_bytes);
  png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);

  if (!png) {
    logger_->log_error("Failed to create PNG write struct");
    return 0;
  }

  png_infop info = png_create_info_struct(png);

  if (!info) {
    logger_->log_error("Failed to create PNG info struct");
    return 0;
  }

  if (setjmp(png_jmpbuf(png))) {
    logger_->log_error("Failed to set PNG jmpbuf");
    return 0;
  }

  try {

    png_set_write_fn(png, this, [](png_structp out_png,
                                   png_bytep out_data,
                                   png_size_t num_bytes) {
                       auto this_callback = reinterpret_cast<PNGWriteCallback *>(png_get_io_ptr(out_png));
                       std::copy(out_data, out_data + num_bytes, std::back_inserter(this_callback->png_output_buf_));
                     },
                     [](png_structp flush_png) {});

    png_set_IHDR(png, info, width_, height_, 8,
                 PNG_COLOR_TYPE_RGB,
                 PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_DEFAULT,
                 PNG_FILTER_TYPE_DEFAULT);
    png_write_info(png, info);

    png_bytep row_pointers[height_];

    for (uint32_t y = 0; y < height_; y++) {
      row_pointers[y] = reinterpret_cast<png_byte *>(frame_->data) + width_ * y * 3;
    }

    png_write_image(png, &row_pointers[0]);
    png_write_end(png, nullptr);

    png_destroy_write_struct(&png, &info);
  } catch (...) {
    if (png && info) {
      png_destroy_write_struct(&png, &info);
    }
    throw;
  }

  return stream->write(png_output_buf_.data(), png_output_buf_.size());
}