168 lines
2.5 KiB
Go
168 lines
2.5 KiB
Go
package imaging
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import (
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"image"
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"math"
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"runtime"
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"sync"
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)
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// parallel processes the data in separate goroutines.
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func parallel(start, stop int, fn func(<-chan int)) {
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count := stop - start
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if count < 1 {
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return
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}
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procs := runtime.GOMAXPROCS(0)
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if procs > count {
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procs = count
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}
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c := make(chan int, count)
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for i := start; i < stop; i++ {
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c <- i
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}
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close(c)
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var wg sync.WaitGroup
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for i := 0; i < procs; i++ {
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wg.Add(1)
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go func() {
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defer wg.Done()
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fn(c)
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}()
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}
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wg.Wait()
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}
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// absint returns the absolute value of i.
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func absint(i int) int {
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if i < 0 {
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return -i
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}
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return i
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}
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// clamp rounds and clamps float64 value to fit into uint8.
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func clamp(x float64) uint8 {
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v := int64(x + 0.5)
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if v > 255 {
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return 255
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}
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if v > 0 {
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return uint8(v)
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}
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return 0
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}
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func reverse(pix []uint8) {
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if len(pix) <= 4 {
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return
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}
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i := 0
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j := len(pix) - 4
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for i < j {
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pi := pix[i : i+4 : i+4]
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pj := pix[j : j+4 : j+4]
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pi[0], pj[0] = pj[0], pi[0]
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pi[1], pj[1] = pj[1], pi[1]
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pi[2], pj[2] = pj[2], pi[2]
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pi[3], pj[3] = pj[3], pi[3]
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i += 4
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j -= 4
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}
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}
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func toNRGBA(img image.Image) *image.NRGBA {
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if img, ok := img.(*image.NRGBA); ok {
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return &image.NRGBA{
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Pix: img.Pix,
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Stride: img.Stride,
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Rect: img.Rect.Sub(img.Rect.Min),
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}
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}
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return Clone(img)
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}
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// rgbToHSL converts a color from RGB to HSL.
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func rgbToHSL(r, g, b uint8) (float64, float64, float64) {
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rr := float64(r) / 255
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gg := float64(g) / 255
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bb := float64(b) / 255
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max := math.Max(rr, math.Max(gg, bb))
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min := math.Min(rr, math.Min(gg, bb))
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l := (max + min) / 2
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if max == min {
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return 0, 0, l
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}
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var h, s float64
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d := max - min
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if l > 0.5 {
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s = d / (2 - max - min)
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} else {
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s = d / (max + min)
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}
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switch max {
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case rr:
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h = (gg - bb) / d
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if g < b {
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h += 6
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}
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case gg:
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h = (bb-rr)/d + 2
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case bb:
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h = (rr-gg)/d + 4
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}
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h /= 6
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return h, s, l
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}
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// hslToRGB converts a color from HSL to RGB.
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func hslToRGB(h, s, l float64) (uint8, uint8, uint8) {
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var r, g, b float64
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if s == 0 {
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v := clamp(l * 255)
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return v, v, v
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}
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var q float64
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if l < 0.5 {
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q = l * (1 + s)
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} else {
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q = l + s - l*s
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}
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p := 2*l - q
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r = hueToRGB(p, q, h+1/3.0)
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g = hueToRGB(p, q, h)
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b = hueToRGB(p, q, h-1/3.0)
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return clamp(r * 255), clamp(g * 255), clamp(b * 255)
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}
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func hueToRGB(p, q, t float64) float64 {
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if t < 0 {
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t++
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}
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if t > 1 {
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t--
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}
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if t < 1/6.0 {
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return p + (q-p)*6*t
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}
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if t < 1/2.0 {
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return q
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}
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if t < 2/3.0 {
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return p + (q-p)*(2/3.0-t)*6
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}
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return p
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}
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