84 lines
1.3 KiB
Go
84 lines
1.3 KiB
Go
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package imaging
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import (
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"image"
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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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pix[i+0], pix[j+0] = pix[j+0], pix[i+0]
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pix[i+1], pix[j+1] = pix[j+1], pix[i+1]
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pix[i+2], pix[j+2] = pix[j+2], pix[i+2]
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pix[i+3], pix[j+3] = pix[j+3], pix[i+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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