Add grayscale image step

config/example.json

@@ -15,10 +15,14 @@
         },
         {
             "name": "rotate image",
-            "type": 0,
+            "type": 1,
             "options": {
                 "angle": 90.0
             }
+        },
+        {
+            "name": "grayscale",
+            "type": 2
         }
     ],
     "output": {

pipelines/executable_step.go

@@ -38,3 +38,14 @@ func (s RotateImageStep) Execute(src image.Image) (image.Image, error) {
 	src = imaging.Rotate(src, s.Options.Angle, image.Black)
 	return src, nil
 }
+
+// Grayscale image
+
+type GrayscaleImageStep struct {
+	Step
+}
+
+func (s GrayscaleImageStep) Execute(src image.Image) (image.Image, error) {
+	src = imaging.Grayscale(src)
+	return src, nil
+}

pipelines/pipeline_test.go

@@ -189,6 +189,50 @@ func TestExecuteSteps(t *testing.T) {
 		os.Remove(storageProvider.GetPath(Bucket, "source.jpg"))
 		os.Remove(storageProvider.GetPath(Bucket, dest))
 	})
+
+	t.Run("Image grayscale step is successful", func(t *testing.T) {
+		const Bucket string = "pipeline_test_05"
+		const Payload string = `{
+			"name": "example pipeline",
+			"type": 1,
+			"removeMetadata": false,
+			"steps": [
+				{
+					"name": "grayscale",
+					"type": 2
+				}
+			]
+		}`
+
+		wd, _ := os.Getwd()
+		pipe := DeserializePipelines([][]byte{[]byte(Payload)})[0]
+
+		storageProvider := storage.GetFileSystemStorageProvider("test", "..")
+
+		// copy test file to storage bucket
+		_, err := storageProvider.StoreExisting(Bucket, "source.jpg", filepath.Join(wd, "../tests/files/900x900.jpg"))
+		assert.Nil(t, err, "Test file should be readable")
+		assert.FileExists(t, storageProvider.GetPath(Bucket, "source.jpg"))
+
+		// run pipeline steps
+		dest, err := pipe.Run("source.jpg", Bucket, storageProvider)
+		assert.Nil(t, err)
+		assert.FileExists(t, storageProvider.GetPath(Bucket, dest))
+
+		// read image config
+		file, err := storageProvider.OpenFile(Bucket, dest)
+		assert.Nil(t, err)
+
+		imgConf, _, err := image.DecodeConfig(file)
+		assert.Nil(t, err)
+
+		assert.Equal(t, 900, imgConf.Width)
+		assert.Equal(t, 900, imgConf.Height)
+
+		// clean up
+		os.Remove(storageProvider.GetPath(Bucket, "source.jpg"))
+		os.Remove(storageProvider.GetPath(Bucket, dest))
+	})
 }
 
 // output options

pipelines/step.go

@@ -10,6 +10,7 @@ type StepType int
 const (
 	TypeResizeImageStep StepType = iota
 	TypeRotateImageStep
+	TypeGrayscaleImageStep
 )
 
 type Step struct {
@@ -34,6 +35,9 @@ func (s Step) GetExecutable() (IExecutableStep, error) {
 			return nil, err
 		}
 		return step, nil
+
+	case TypeGrayscaleImageStep:
+		return GrayscaleImageStep{}, nil
 	}
 
 	return nil, errors.New("invalid type")