Method writePng

source/core/StarImage.cpp:474–524

}

void Image::writePng(IODevicePtr device) const {
  auto writePngData = [](png_structp pngPtr, png_bytep data, png_size_t length) {
    IODevice* device = (IODevice*)png_get_io_ptr(pngPtr);
    device->writeFull((char*)data, length);
  };

  auto flushPngData = [](png_structp) {};

  png_structp png_ptr = nullptr;
  png_infop info_ptr = nullptr;

  png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
  if (!png_ptr)
    throw ImageException("Internal libPNG error");

  info_ptr = png_create_info_struct(png_ptr);
  if (!info_ptr) {
    png_destroy_write_struct(&png_ptr, nullptr);
    throw ImageException("Internal libPNG error");
  }

  if (setjmp(png_jmpbuf(png_ptr))) {
    png_destroy_write_struct(&png_ptr, &info_ptr);
    throw ImageException("Internal error reading png.");
  }

  unsigned channels = m_pixelFormat == PixelFormat::RGB24 ? 3 : 4;

  png_set_IHDR(png_ptr,
      info_ptr,
      m_width,
      m_height,
      8,
      channels == 3 ? PNG_COLOR_TYPE_RGB : PNG_COLOR_TYPE_RGBA,
      PNG_INTERLACE_NONE,
      PNG_COMPRESSION_TYPE_DEFAULT,
      PNG_FILTER_TYPE_DEFAULT);

  unique_ptr<png_bytep[]> row_ptrs(new png_bytep[m_height]);
  size_t stride = m_width * 8 * channels / 8;
  for (size_t i = 0; i < m_height; ++i) {
    size_t q = (m_height - i - 1) * stride;
    row_ptrs[i] = (png_bytep)m_data + q;
  }

  png_set_write_fn(png_ptr, device.get(), writePngData, flushPngData);
  png_set_rows(png_ptr, info_ptr, row_ptrs.get());
  png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, nullptr);

  png_destroy_write_struct(&png_ptr, &info_ptr);
}

ImageView::ImageView(Image const& image) {
  size = image.size();