1 files changed, 27 insertions, 19 deletions

diff --git a/vendor/github.com/disintegration/imaging/histogram.go b/vendor/github.com/disintegration/imaging/histogram.go
index 967ee6a25..5bcb001ca 100644
--- a/vendor/github.com/disintegration/imaging/histogram.go
+++ b/vendor/github.com/disintegration/imaging/histogram.go
@@ -2,6 +2,7 @@ package imaging
 
 import (
 	"image"
+	"sync"
 )
 
 // Histogram returns a normalized histogram of an image.
@@ -9,35 +10,42 @@ import (
 // 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 {
-	src := toNRGBA(img)
-	width := src.Bounds().Max.X
-	height := src.Bounds().Max.Y
-
+	var mu sync.Mutex
 	var histogram [256]float64
 	var total float64
 
-	if width == 0 || height == 0 {
+	src := newScanner(img)
+	if src.w == 0 || src.h == 0 {
 		return histogram
 	}
 
-	for y := 0; y < height; y++ {
-		for x := 0; x < width; x++ {
-			i := y*src.Stride + x*4
-
-			r := src.Pix[i+0]
-			g := src.Pix[i+1]
-			b := src.Pix[i+2]
-
-			y := 0.299*float32(r) + 0.587*float32(g) + 0.114*float32(b)
-
-			histogram[int(y+0.5)]++
-			total++
+	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
 }