Merge branch 'disintegration-pixel_coordinate'

filters.go

@@ -87,7 +87,7 @@ func createWeights8(dy, filterLength int, blur, scale float64, kernel func(float
 	coeffs := make([]int16, dy*filterLength)
 	start := make([]int, dy)
 	for y := 0; y < dy; y++ {
-		interpX := scale * (float64(y) + 0.5)
+		interpX := scale*(float64(y)+0.5) - 0.5
 		start[y] = int(interpX) - filterLength/2 + 1
 		interpX -= float64(start[y])
 		for i := 0; i < filterLength; i++ {
@@ -107,7 +107,7 @@ func createWeights16(dy, filterLength int, blur, scale float64, kernel func(floa
 	coeffs := make([]int32, dy*filterLength)
 	start := make([]int, dy)
 	for y := 0; y < dy; y++ {
-		interpX := scale * (float64(y) + 0.5)
+		interpX := scale*(float64(y)+0.5) - 0.5
 		start[y] = int(interpX) - filterLength/2 + 1
 		interpX -= float64(start[y])
 		for i := 0; i < filterLength; i++ {
@@ -126,7 +126,7 @@ func createWeightsNearest(dy, filterLength int, blur, scale float64) ([]bool, []
 	coeffs := make([]bool, dy*filterLength)
 	start := make([]int, dy)
 	for y := 0; y < dy; y++ {
-		interpX := scale * (float64(y) + 0.5)
+		interpX := scale*(float64(y)+0.5) - 0.5
 		start[y] = int(interpX) - filterLength/2 + 1
 		interpX -= float64(start[y])
 		for i := 0; i < filterLength; i++ {

resize_test.go

@@ -85,6 +85,26 @@ func Test_SameSizeReturnsOriginal(t *testing.T) {
 	}
 }
 
+func Test_PixelCoordinates(t *testing.T) {
+	checkers := image.NewGray(image.Rect(0, 0, 4, 4))
+	checkers.Pix = []uint8{
+		255, 0, 255, 0,
+		0, 255, 0, 255,
+		255, 0, 255, 0,
+		0, 255, 0, 255,
+	}
+
+	resized := Resize(12, 12, checkers, NearestNeighbor).(*image.Gray)
+
+	if resized.Pix[0] != 255 || resized.Pix[1] != 255 || resized.Pix[2] != 255 {
+		t.Fail()
+	}
+
+	if resized.Pix[3] != 0 || resized.Pix[4] != 0 || resized.Pix[5] != 0 {
+		t.Fail()
+	}
+}
+
 const (
 	// Use a small image size for benchmarks. We don't want memory performance
 	// to affect the benchmark results.