[performance] use single-threaded image transforms (#3252)

* use single-threaded image resizing in native code so we have more control over goroutines

* implement parallel-free versions of image transform functions also

* remove debug code

1 files changed, 0 insertions, 52 deletions

diff --git a/vendor/github.com/disintegration/imaging/histogram.go b/vendor/github.com/disintegration/imaging/histogram.go
deleted file mode 100644
index c547fe822..000000000
--- a/vendor/github.com/disintegration/imaging/histogram.go
+++ /dev/null
@@ -1,52 +0,0 @@
-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++ {
-				s := scanLine[i : i+3 : i+3]
-				r := s[0]
-				g := s[1]
-				b := s[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
-}