func p(x, y int) ft.RastPoint {
return ft.RastPoint{
X: ft.Fix32(x * 256),
Y: ft.Fix32(y * 256),
}
}
func main() {
const (
n = 17
r = 256 * 80
)
s := ft.Fix32(r * math.Sqrt(2) / 2)
t := ft.Fix32(r * math.Tan(math.Pi/8))
m := image.NewRGBA(image.Rect(0, 0, 800, 600))
draw.Draw(m, m.Bounds(), image.NewUniform(color.RGBA{63, 63, 63, 255}), image.ZP, draw.Src)
mp := ft.NewRGBADrawer(m)
mp.SetColor(image.Black)
z := ft.NewRast(800, 600)
for i := 0; i < n; i++ {
cx := ft.Fix32(25600 + 51200*(i%4))
cy := ft.Fix32(2560 + 32000*(i/4))
c := ft.RastPoint{X: cx, Y: cy}
theta := math.Pi * (0.5 + 0.5*float64(i)/(n-1))
dx := ft.Fix32(r * math.Cos(theta))
dy := ft.Fix32(r * math.Sin(theta))
d := ft.RastPoint{X: dx, Y: dy}
// Draw a quarter-circle approximated by two quadratic segments,
// with each segment spanning 45 degrees.
z.Start(c)
z.Add1(c.Add(ft.RastPoint{X: r, Y: 0}))
z.Add2(c.Add(ft.RastPoint{X: r, Y: t}), c.Add(ft.RastPoint{X: s, Y: s}))
z.Add2(c.Add(ft.RastPoint{X: t, Y: r}), c.Add(ft.RastPoint{X: 0, Y: r}))
// Add another quadratic segment whose angle ranges between 0 and 90 degrees.
// For an explanation of the magic constants 22, 150, 181 and 256, read the
// comments in the freetype/ft package.
dot := 256 * d.Dot(ft.RastPoint{X: 0, Y: r}) / (r * r)
multiple := ft.Fix32(150 - 22*(dot-181)/(256-181))
z.Add2(c.Add(ft.RastPoint{X: dx, Y: r + dy}.Mul(multiple)), c.Add(d))
// Close the curve.
z.Add1(c)
}
z.Rast(mp)
for i := 0; i < n; i++ {
cx := ft.Fix32(25600 + 51200*(i%4))
cy := ft.Fix32(2560 + 32000*(i/4))
for j := 0; j < n; j++ {
theta := math.Pi * float64(j) / (n - 1)
dx := ft.Fix32(r * math.Cos(theta))
dy := ft.Fix32(r * math.Sin(theta))
m.Set(int((cx+dx)/256), int((cy+dy)/256), color.RGBA{255, 255, 0, 255})
}
}
// Save that RGBA image to disk.
f, err := os.Create("round.png")
if err != nil {
log.Println(err)
os.Exit(1)
}
defer f.Close()
b := bufio.NewWriter(f)
err = png.Encode(b, m)
if err != nil {
log.Println(err)
os.Exit(1)
}
err = b.Flush()
if err != nil {
log.Println(err)
os.Exit(1)
}
fmt.Println("Wrote round.png OK.")
}