func drawPixels(img *image.Alpha, px, py, pw, ph uint, fill bool) {
var x, y uint
for y = 0; y < ph; y++ {
for x = 0; x < pw; x++ {
if fill {
img.Set(int(px*pw+x), int(py*ph+y), image.White)
} else {
img.Set(int(px*pw+x), int(py*ph+y), image.Transparent)
}
}
}
}
