Implementation of the draw function and color constant

colors.go

@@ -0,0 +1,29 @@
+package cvutils
+
+var (
+	Black = Color{
+		Red:   0,
+		Green: 0,
+		Blue:  0,
+	}
+	White = Color{
+		Red:   255,
+		Green: 255,
+		Blue:  255,
+	}
+	Red = Color{
+		Red:   255,
+		Green: 0,
+		Blue:  0,
+	}
+	Green = Color{
+		Red:   0,
+		Green: 255,
+		Blue:  0,
+	}
+	Blue = Color{
+		Red:   0,
+		Green: 0,
+		Blue:  255,
+	}
+)

draw.go

@@ -0,0 +1,74 @@
+package cvutils
+
+import (
+	"errors"
+	"fmt"
+	"log"
+
+	"gocv.io/x/gocv"
+)
+
+type ImageOptions struct {
+	Name       string
+	Flags      gocv.IMReadFlag
+	WindowName string
+	Draw       DrawOptions
+}
+
+type DrawOptions struct {
+	DrawFunc      DrawFunc
+	Color         Color
+	StartingPoint Point
+	EndPoint      Point
+}
+
+type Point struct {
+	X int
+	Y int
+}
+
+type DrawFunc func(image Image, color Color, point Point)
+
+func ensureImageCanBeDraw(dimensions []int, points []Point) error {
+	for _, point := range points {
+		if point.X > dimensions[0] || point.Y > dimensions[1] {
+			return errors.New(fmt.Sprintf("The point: %v is greater "+
+				"than the upper limit of the image: x = %v y = %v", point, dimensions[0], dimensions[1]))
+		}
+	}
+
+	return nil
+}
+
+func ShowIMG(opts ImageOptions) {
+	img := Image{
+		Mat: gocv.IMRead(opts.Name, opts.Flags),
+	}
+
+	if img.Mat.Empty() {
+		log.Fatal(fmt.Sprintf("Error reading image from: %v\n", opts.Name))
+	}
+
+	defer img.Mat.Close()
+
+	if err := ensureImageCanBeDraw(img.Mat.Size(), []Point{
+		opts.Draw.StartingPoint,
+		opts.Draw.EndPoint,
+	}); err != nil {
+		log.Fatal(err.Error())
+	}
+
+	window := gocv.NewWindow(opts.WindowName)
+
+	for i := opts.Draw.StartingPoint.X; i < opts.Draw.EndPoint.X; i++ {
+		for j := opts.Draw.StartingPoint.Y; j < opts.Draw.EndPoint.Y; j++ {
+			opts.Draw.DrawFunc(img, opts.Draw.Color, Point{
+				X: i,
+				Y: j,
+			})
+		}
+	}
+
+	window.IMShow(img.Mat)
+	window.WaitKey(0)
+}