func PixelZoom(xfactor float32, yfactor float32) {
	syscall.Syscall(gpPixelZoom, 2, uintptr(math.Float32bits(xfactor)), uintptr(math.Float32bits(yfactor)), 0)
}
func PixelZoom(xfactor float32, yfactor float32) {
	syscall.Syscall(gpPixelZoom, 2, uintptr(math.Float32bits(xfactor)), uintptr(math.Float32bits(yfactor)), 0)
}
// specify the pixel zoom factors