Cogl.Bitmap.prototype.get_buffer

function get_buffer(): Cogl.PixelBuffer {
    // Gjs wrapper for cogl_bitmap_get_buffer()
}

Since 1.10

Returns: the Cogl.PixelBuffer that this buffer uses for storage. Note that if the bitmap was created with Cogl.Bitmap.new_from_file then it will not actually be using a pixel buffer and this function will return null.