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