// average convert the sums to averages and returns the result.
func average(sum []uint64, w, h int, n uint64) tipimage.Image {
ret := tipimage.NewRGBA(tipimage.Rect(0, 0, w, h))
for y := 0; y < h; y++ {
for x := 0; x < w; x++ {
index := 4 * (y*w + x)
ret.SetRGBA(x, y, color.RGBA{
uint8(sum[index+0] / n),
uint8(sum[index+1] / n),
uint8(sum[index+2] / n),
uint8(sum[index+3] / n),
})
}
}
return ret
}
// Resample returns a resampled copy of the tipimage slice r of m.
// The returned tipimage has width w and height h.
func Resample(m tipimage.Image, r tipimage.Rectangle, w, h int) tipimage.Image {
if w < 0 || h < 0 {
return nil
}
if w == 0 || h == 0 || r.Dx() <= 0 || r.Dy() <= 0 {
return tipimage.NewRGBA64(tipimage.Rect(0, 0, w, h))
}
curw, curh := r.Dx(), r.Dy()
img := tipimage.NewRGBA(tipimage.Rect(0, 0, w, h))
for y := 0; y < h; y++ {
for x := 0; x < w; x++ {
// Get a source pixel.
subx := x * curw / w
suby := y * curh / h
r32, g32, b32, a32 := m.At(subx, suby).RGBA()
r := uint8(r32 >> 8)
g := uint8(g32 >> 8)
b := uint8(b32 >> 8)
a := uint8(a32 >> 8)
img.SetRGBA(x, y, color.RGBA{r, g, b, a})
}
}
return img
}