// moustache draws a moustache of the specified size and droop
// onto the image m and returns the result. It may overwrite the
// original.
func moustache(m image.Image, x, y, size, droopFactor int) image.Image {
mrgba := rgba(m)
p := raster.NewRGBAPainter(mrgba)
p.SetColor(color.RGBA{0, 0, 0, 255})
w, h := m.Bounds().Dx(), m.Bounds().Dy()
r := raster.NewRasterizer(w, h)
var (
mag = raster.Fix32((10 + size) << 8)
width = pt(20, 0).Mul(mag)
mid = pt(x, y)
droop = pt(0, droopFactor).Mul(mag)
left = mid.Sub(width).Add(droop)
right = mid.Add(width).Add(droop)
bow = pt(0, 5).Mul(mag).Sub(droop)
curlx = pt(10, 0).Mul(mag)
curly = pt(0, 2).Mul(mag)
risex = pt(2, 0).Mul(mag)
risey = pt(0, 5).Mul(mag)
)
r.Start(left)
r.Add3(
mid.Sub(curlx).Add(curly),
mid.Sub(risex).Sub(risey),
mid,
)
r.Add3(
mid.Add(risex).Sub(risey),
mid.Add(curlx).Add(curly),
right,
)
r.Add2(
mid.Add(bow),
left,
)
r.Rasterize(p)
return mrgba
}
// pt returns the raster.Point corresponding to the pixel position (x, y).
func pt(x, y int) raster.Point {
return raster.Point{raster.Fix32(x << 8), raster.Fix32(y << 8)}
}