Added RotateFlag type

Rotate function accepts an integer rotate code. This opens a potential
security hole as a user can submit any integer which will cause the code
to hang.

By introducing RotateFlag as per cv::RotateFlags enum which is passed to
cv::rotate we eliminate this possibility and in turn gain cleaner code,
happy users and sucessful builds.

core.go

@@ -871,11 +871,27 @@ func Vconcat(src1, src2 Mat, dst *Mat) {
 	C.Mat_Vconcat(src1.p, src2.p, dst.p)
 }
 
+// RotateFlag for image rotation
+//
+
+// For further details please see:
+// https://docs.opencv.org/master/d2/de8/group__core__array.html#ga6f45d55c0b1cc9d97f5353a7c8a7aac2
+type RotateFlag int
+
+const (
+	// Rotate90Clockwise allows to rotate image 90 degrees clockwise
+	Rotate90Clockwise RotateFlag = 0
+	// Rotate180Clockwise allows to rotate image 180 degrees clockwise
+	Rotate180Clockwise = 1
+	// Rotate90CounterClockwise allows to rotate 270 degrees clockwise
+	Rotate90CounterClockwise = 2
+)
+
 // Rotate rotates a 2D array in multiples of 90 degrees
 //
 // For further details, please see:
 // https://docs.opencv.org/master/d2/de8/group__core__array.html#ga4ad01c0978b0ce64baa246811deeac24
-func Rotate(src Mat, dst *Mat, code int) {
+func Rotate(src Mat, dst *Mat, code RotateFlag) {
 	C.Rotate(src.p, dst.p, C.int(code))
 }
 

core_test.go

@@ -938,10 +938,18 @@ func TestRotate(t *testing.T) {
 	dst := NewMat()
 	defer dst.Close()
 
-	Rotate(src, &dst, 0)
+	Rotate(src, &dst, Rotate90Clockwise)
 	if dst.Rows() != 2 {
 		t.Errorf("expected rows: %d got %d", src.Cols(), dst.Rows())
 	}
+
+	dst2src := NewMat()
+	defer dst2src.Close()
+
+	Rotate(dst, &dst2src, Rotate90CounterClockwise)
+	if dst2src.Rows() != 1 {
+		t.Errorf("expected rows: %d got %d", src.Rows(), dst2src.Rows())
+	}
 }
 
 func TestMatIdct(t *testing.T) {