void Write(const std::string& filename) {
        FILE* fp = fopen(filename.c_str(), "wb");
        if (!fp) {
            throw std::runtime_error("Can't open file " + filename);
        }

        png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
        if (!png) {
            throw std::runtime_error("Can't create png write struct");
        }

        png_infop info = png_create_info_struct(png);
        if (!info) {
            throw std::runtime_error("Can't create png info struct");
        }

        if (setjmp(png_jmpbuf(png))) {
            abort();
        }

        png_init_io(png, fp);

        // Output is 8bit depth, RGBA format.
        png_set_IHDR(png, info, width_, height_, 8, PNG_COLOR_TYPE_RGBA, PNG_INTERLACE_NONE,
                     PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
        png_write_info(png, info);

        // To remove the alpha channel for PNG_COLOR_TYPE_RGB format,
        // Use png_set_filler().
        // png_set_filler(png, 0, PNG_FILLER_AFTER);

        png_write_image(png, bytes_);
        png_write_end(png, nullptr);

        fclose(fp);
        png_destroy_write_struct(&png, &info);
    }