Update processor grayscale logic

pkg/processor/native/processor.go

@@ -3,7 +3,7 @@ package native
 import (
 	"bytes"
 	"github.com/anthonynsimon/bild/clone"
-	"github.com/anthonynsimon/bild/effect"
+	"github.com/anthonynsimon/bild/parallel"
 	"github.com/anthonynsimon/bild/transform"
 	"image"
 	"image/color"
@@ -98,12 +98,30 @@ func (bp *BildProcessor) GrayScale(input []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-
-	img = effect.Grayscale(img)
+	img = grayScale(img)
 
 	return bp.encode(img, f)
 }
 
+func grayScale(img image.Image) image.Image {
+	src := clone.AsRGBA(img)
+	bounds := src.Bounds()
+	if bounds.Empty() {
+		return &image.RGBA{}
+	}
+	dst := image.NewRGBA(bounds)
+	parallel.Line(bounds.Dy(), func(start, end int) {
+		for y := start; y < end; y++ {
+			for x := 0; x < bounds.Dx(); x++ {
+				srcPix := src.At(x, y).(color.RGBA)
+				g := color.GrayModel.Convert(srcPix).(color.Gray).Y
+				dst.Set(x, y, color.RGBA{R: g, G: g, B: g, A: srcPix.A})
+			}
+		}
+	})
+	return dst
+}
+
 func (bp *BildProcessor) decode(data []byte) (image.Image, string, error) {
 	t := time.Now()
 	img, f, err := image.Decode(bytes.NewReader(data))

pkg/processor/native/processor_test.go

@@ -20,8 +20,8 @@ type BildProcessorSuite struct {
 
 func (s *BildProcessorSuite) SetupSuite() {
 	s.processor = NewBildProcessor()
-	s.srcData, _ = ioutil.ReadFile("test.png")
-	s.watermarkData, _ = ioutil.ReadFile("overlay.png")
+	s.srcData, _ = ioutil.ReadFile("_testdata/test.png")
+	s.watermarkData, _ = ioutil.ReadFile("_testdata/overlay.png")
 	s.badData = []byte("badImage.ext")
 }
 
@@ -52,11 +52,17 @@ func (s *BildProcessorSuite) TestBildProcessor_Crop() {
 }
 
 func (s *BildProcessorSuite) TestBildProcessor_Grayscale() {
-	output, err := s.processor.GrayScale(s.srcData)
+	var actual, expected []byte
+	var err error
+	actual, err = s.processor.GrayScale(s.srcData)
+	assert.NotNil(s.T(), actual)
+	assert.Nil(s.T(), err)
 
-	assert.NotNil(s.T(), output)
+	expected, err = ioutil.ReadFile("_testdata/test_grayscaled.png")
+	assert.NotNil(s.T(), expected)
 	assert.Nil(s.T(), err)
-	assert.NotEqual(s.T(), s.srcData, output)
+
+	assert.EqualValues(s.T(), actual, expected)
 }
 
 func (s *BildProcessorSuite) TestBildProcessor_Watermark() {