52 lines
1.1 KiB
Go
52 lines
1.1 KiB
Go
|
package imaging
|
||
|
|
|
||
|
|
import (
|
||
|
|
"image"
|
||
|
|
"sync"
|
||
|
|
)
|
||
|
|
|
||
|
|
// Histogram returns a normalized histogram of an image.
|
||
|
|
//
|
||
|
|
// Resulting histogram is represented as an array of 256 floats, where
|
||
|
|
// histogram[i] is a probability of a pixel being of a particular luminance i.
|
||
|
|
func Histogram(img image.Image) [256]float64 {
|
||
|
|
var mu sync.Mutex
|
||
|
|
var histogram [256]float64
|
||
|
|
var total float64
|
||
|
|
|
||
|
|
src := newScanner(img)
|
||
|
|
if src.w == 0 || src.h == 0 {
|
||
|
|
return histogram
|
||
|
|
}
|
||
|
|
|
||
|
|
parallel(0, src.h, func(ys <-chan int) {
|
||
|
|
var tmpHistogram [256]float64
|
||
|
|
var tmpTotal float64
|
||
|
|
scanLine := make([]uint8, src.w*4)
|
||
|
|
for y := range ys {
|
||
|
|
src.scan(0, y, src.w, y+1, scanLine)
|
||
|
|
i := 0
|
||
|
|
for x := 0; x < src.w; x++ {
|
||
|
|
r := scanLine[i+0]
|
||
|
|
g := scanLine[i+1]
|
||
|
|
b := scanLine[i+2]
|
||
|
|
y := 0.299*float32(r) + 0.587*float32(g) + 0.114*float32(b)
|
||
|
|
tmpHistogram[int(y+0.5)]++
|
||
|
|
tmpTotal++
|
||
|
|
i += 4
|
||
|
|
}
|
||
|
|
}
|
||
|
|
mu.Lock()
|
||
|
|
for i := 0; i < 256; i++ {
|
||
|
|
histogram[i] += tmpHistogram[i]
|
||
|
|
}
|
||
|
|
total += tmpTotal
|
||
|
|
mu.Unlock()
|
||
|
|
})
|
||
|
|
|
||
|
|
for i := 0; i < 256; i++ {
|
||
|
|
histogram[i] = histogram[i] / total
|
||
|
|
}
|
||
|
|
return histogram
|
||
|
|
}
|