Merge branch 'charlievieth-master'

converter.go

@@ -20,24 +20,27 @@ import "image"
 
 // Keep value in [0,255] range.
 func clampUint8(in int32) uint8 {
-	if in < 0 {
+	// casting a negative int to an uint will result in an overflown large int.
-		return 0
+	// this behavior will be exploited here and in other functions to archive
+	// a higher performance.
+	if uint32(in) < 256 {
+		return uint8(in)
 	}
 	if in > 255 {
 		return 255
 	}
-	return uint8(in)
+	return 0
 }
 
 // Keep value in [0,65535] range.
 func clampUint16(in int64) uint16 {
-	if in < 0 {
+	if uint64(in) < 65536 {
-		return 0
+		return uint16(in)
 	}
 	if in > 65535 {
 		return 65535
 	}
-	return uint16(in)
+	return 0
 }
 
 func resizeGeneric(in image.Image, out *image.RGBA64, scale float64, coeffs []int32, offset []int, filterLength int) {
@@ -102,12 +105,12 @@ func resizeRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []int16,
 				if coeff != 0 {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 4
 					case xi >= maxX:
 						xi = 4 * maxX
 					default:
-						xi *= 4
+						xi = 0
 					}
 					rgba[0] += int32(coeff) * int32(row[xi+0])
 					rgba[1] += int32(coeff) * int32(row[xi+1])
@@ -142,12 +145,12 @@ func resizeRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []i
 				if coeff != 0 {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 8
 					case xi >= maxX:
 						xi = 8 * maxX
 					default:
-						xi *= 8
+						xi = 0
 					}
 					rgba[0] += int64(coeff) * int64(uint16(row[xi+0])<<8|uint16(row[xi+1]))
 					rgba[1] += int64(coeff) * int64(uint16(row[xi+2])<<8|uint16(row[xi+3]))
@@ -222,12 +225,12 @@ func resizeGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []i
 				if coeff != 0 {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 2
 					case xi >= maxX:
 						xi = 2 * maxX
 					default:
-						xi *= 2
+						xi = 0
 					}
 					gray += int64(coeff) * int64(uint16(row[xi+0])<<8|uint16(row[xi+1]))
 					sum += int64(coeff)
@@ -258,12 +261,12 @@ func resizeYCbCr(in *ycc, out *ycc, scale float64, coeffs []int16, offset []int,
 				if coeff != 0 {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 3
 					case xi >= maxX:
 						xi = 3 * maxX
 					default:
-						xi *= 3
+						xi = 0
 					}
 					p[0] += int32(coeff) * int32(row[xi+0])
 					p[1] += int32(coeff) * int32(row[xi+1])
@@ -295,12 +298,12 @@ func nearestYCbCr(in *ycc, out *ycc, scale float64, coeffs []bool, offset []int,
 				if coeffs[ci+i] {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 3
 					case xi >= maxX:
 						xi = 3 * maxX
 					default:
-						xi *= 3
+						xi = 0
 					}
 					p[0] += float32(row[xi+0])
 					p[1] += float32(row[xi+1])

nearest.go

@@ -94,12 +94,12 @@ func nearestRGBA(in *image.RGBA, out *image.RGBA, scale float64, coeffs []bool,
 				if coeffs[ci+i] {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 4
 					case xi >= maxX:
 						xi = 4 * maxX
 					default:
-						xi *= 4
+						xi = 0
 					}
 					rgba[0] += float32(row[xi+0])
 					rgba[1] += float32(row[xi+1])
@@ -133,12 +133,12 @@ func nearestRGBA64(in *image.RGBA64, out *image.RGBA64, scale float64, coeffs []
 				if coeffs[ci+i] {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 8
 					case xi >= maxX:
 						xi = 8 * maxX
 					default:
-						xi *= 8
+						xi = 0
 					}
 					rgba[0] += float32(uint16(row[xi+0])<<8 | uint16(row[xi+1]))
 					rgba[1] += float32(uint16(row[xi+2])<<8 | uint16(row[xi+3]))
@@ -211,12 +211,12 @@ func nearestGray16(in *image.Gray16, out *image.Gray16, scale float64, coeffs []
 				if coeffs[ci+i] {
 					xi := start + i
 					switch {
-					case xi < 0:
+					case uint(xi) < uint(maxX):
-						xi = 0
+						xi *= 2
 					case xi >= maxX:
 						xi = 2 * maxX
 					default:
-						xi *= 2
+						xi = 0
 					}
 					gray += float32(uint16(row[xi+0])<<8 | uint16(row[xi+1]))
 					sum++

resize.go

@@ -97,7 +97,7 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
 	}
 
 	taps, kernel := interp.kernel()
-	cpus := runtime.NumCPU()
+	cpus := runtime.GOMAXPROCS(0)
 	wg := sync.WaitGroup{}
 
 	// Generic access to image.Image is slow in tight loops.
@@ -283,7 +283,7 @@ func Resize(width, height uint, img image.Image, interp InterpolationFunction) i
 
 func resizeNearest(width, height uint, scaleX, scaleY float64, img image.Image, interp InterpolationFunction) image.Image {
 	taps, _ := interp.kernel()
-	cpus := runtime.NumCPU()
+	cpus := runtime.GOMAXPROCS(0)
 	wg := sync.WaitGroup{}
 
 	switch input := img.(type) {

resize_test.go

@@ -85,56 +85,105 @@ func Test_SameSizeReturnsOriginal(t *testing.T) {
 	}
 }
 
-func Benchmark_BigResizeLanczos3(b *testing.B) {
+const (
-	var m image.Image
+	// Use a small image size for benchmarks. We don't want memory performance
+	// to affect the benchmark results.
+	benchMaxX = 250
+	benchMaxY = 250
+
+	// Resize values near the original size require increase the amount of time
+	// resize spends converting the image.
+	benchWidth  = 200
+	benchHeight = 200
+)
+
+func benchRGBA(b *testing.B, interp InterpolationFunction) {
+	m := image.NewRGBA(image.Rect(0, 0, benchMaxX, benchMaxY))
+	// Initialize m's pixels to create a non-uniform image.
+	for y := m.Rect.Min.Y; y < m.Rect.Max.Y; y++ {
+		for x := m.Rect.Min.X; x < m.Rect.Max.X; x++ {
+			i := m.PixOffset(x, y)
+			m.Pix[i+0] = uint8(y + 4*x)
+			m.Pix[i+1] = uint8(y + 4*x)
+			m.Pix[i+2] = uint8(y + 4*x)
+			m.Pix[i+3] = uint8(4*y + x)
+		}
+	}
+
+	var out image.Image
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		m = Resize(1000, 1000, img, Lanczos3)
+		out = Resize(benchWidth, benchHeight, m, interp)
 	}
-	m.At(0, 0)
+	out.At(0, 0)
 }
 
-func Benchmark_Reduction(b *testing.B) {
+// The names of some interpolation functions are truncated so that the columns
-	largeImg := image.NewRGBA(image.Rect(0, 0, 1000, 1000))
+// of 'go test -bench' line up.
+func Benchmark_Nearest_RGBA(b *testing.B) {
+	benchRGBA(b, NearestNeighbor)
+}
 
-	var m image.Image
+func Benchmark_Bilinear_RGBA(b *testing.B) {
+	benchRGBA(b, Bilinear)
+}
+
+func Benchmark_Bicubic_RGBA(b *testing.B) {
+	benchRGBA(b, Bicubic)
+}
+
+func Benchmark_Mitchell_RGBA(b *testing.B) {
+	benchRGBA(b, MitchellNetravali)
+}
+
+func Benchmark_Lanczos2_RGBA(b *testing.B) {
+	benchRGBA(b, Lanczos2)
+}
+
+func Benchmark_Lanczos3_RGBA(b *testing.B) {
+	benchRGBA(b, Lanczos3)
+}
+
+func benchYCbCr(b *testing.B, interp InterpolationFunction) {
+	m := image.NewYCbCr(image.Rect(0, 0, benchMaxX, benchMaxY), image.YCbCrSubsampleRatio422)
+	// Initialize m's pixels to create a non-uniform image.
+	for y := m.Rect.Min.Y; y < m.Rect.Max.Y; y++ {
+		for x := m.Rect.Min.X; x < m.Rect.Max.X; x++ {
+			yi := m.YOffset(x, y)
+			ci := m.COffset(x, y)
+			m.Y[yi] = uint8(16*y + x)
+			m.Cb[ci] = uint8(y + 16*x)
+			m.Cr[ci] = uint8(y + 16*x)
+		}
+	}
+	var out image.Image
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		m = Resize(300, 300, largeImg, Bicubic)
+		out = Resize(benchWidth, benchHeight, m, interp)
 	}
-	m.At(0, 0)
+	out.At(0, 0)
 }
 
-// Benchmark resize of 16 MPix jpeg image to 800px width.
+func Benchmark_Nearest_YCC(b *testing.B) {
-func jpegThumb(b *testing.B, interp InterpolationFunction) {
+	benchYCbCr(b, NearestNeighbor)
-	input := image.NewYCbCr(image.Rect(0, 0, 4896, 3264), image.YCbCrSubsampleRatio422)
-
-	var output image.Image
-	for i := 0; i < b.N; i++ {
-		output = Resize(800, 0, input, interp)
 }
 
-	output.At(0, 0)
+func Benchmark_Bilinear_YCC(b *testing.B) {
+	benchYCbCr(b, Bilinear)
 }
 
-func Benchmark_LargeJpegThumbNearestNeighbor(b *testing.B) {
+func Benchmark_Bicubic_YCC(b *testing.B) {
-	jpegThumb(b, NearestNeighbor)
+	benchYCbCr(b, Bicubic)
 }
 
-func Benchmark_LargeJpegThumbBilinear(b *testing.B) {
+func Benchmark_Mitchell_YCC(b *testing.B) {
-	jpegThumb(b, Bilinear)
+	benchYCbCr(b, MitchellNetravali)
 }
 
-func Benchmark_LargeJpegThumbBicubic(b *testing.B) {
+func Benchmark_Lanczos2_YCC(b *testing.B) {
-	jpegThumb(b, Bicubic)
+	benchYCbCr(b, Lanczos2)
 }
 
-func Benchmark_LargeJpegThumbMitchellNetravali(b *testing.B) {
+func Benchmark_Lanczos3_YCC(b *testing.B) {
-	jpegThumb(b, MitchellNetravali)
+	benchYCbCr(b, Lanczos3)
-}
-
-func Benchmark_LargeJpegThumbLanczos2(b *testing.B) {
-	jpegThumb(b, Lanczos2)
-}
-
-func Benchmark_LargeJpegThumbLanczos3(b *testing.B) {
-	jpegThumb(b, Lanczos3)
 }