Golang : Add text to image and get OpenCV's X, Y co-ordinates example



Tags : golang GUI openCV putText color time

Building on from the previous OpenCV-GTK-GUI application tutorial. For this tutorial, I need to know where to position my text on the camera feed. To be precise, I need to know the X and Y coordinates returned by Go-OpenCV's Point struct for top-left, top-right, bottom-left and bottom-right locations. Also, I need to be able to control the text position with two sliders(scrollbars or trackbars).

put text and init font opencv golang example

The code example that follows will write a simple "Hello World" string and the current time on screen (camera feed) and allow us to control the text's position.

Here you go!


 package main

 import (
 "fmt"
 "strconv"
 "time"

 "github.com/lazywei/go-opencv/opencv"
 "github.com/mattn/go-gtk/glib"
 "github.com/mattn/go-gtk/gtk"
 )

 var (
 win = new(opencv.Window)
 webCamera = new(opencv.Capture)
 statusbar = new(gtk.Statusbar)
 snapshotFileName string
 width, height int
 sliderPosX, sliderPosY int
 horizontalScale = float32(1.0)
 verticalScale = float32(1.0)
 shear = float32(1.0)
 thickness = 3
 lineType = 8
 textFont = opencv.InitFont(opencv.CV_FONT_HERSHEY_SIMPLEX, horizontalScale, verticalScale, shear, thickness, lineType)
 )

 func processFrameAndUpdate() {

 for {

 if webCamera.GrabFrame() {
 IplImgFrame := webCamera.RetrieveFrame(1)
 if IplImgFrame != nil {

 //IplImgFrame = opencv.Resize(IplImgFrame, 0, height-200, opencv.CV_INTER_LINEAR)

 // https://godoc.org/github.com/lazywei/go-opencv/opencv#NewScalar
 redColor := opencv.NewScalar(0, 0, 255, 0) // red - (blue, green, red, alpha)
 cyanColor := opencv.NewScalar(255, 255, 0, 0) // cyan - (blue, green, red, alpha)

 position := opencv.Point{sliderPosX, sliderPosY}

 // see https://www.socketloop.com/tutorials/golang-get-current-time
 currentTime := time.Now().Local().Format("2006-01-02 15:04:05 +0800")

 textFont.PutText(IplImgFrame, "Hello World! ", position, redColor)
 textFont.PutText(IplImgFrame, currentTime, opencv.Point{sliderPosX, sliderPosY + int(verticalScale*30.0)}, cyanColor)

 win.ShowImage(IplImgFrame)

 }
 }

 }

 }

 func main() {

 // a new OpenCV window
 win = opencv.NewWindow("Go-OpenCV camera feed for Gtk-GUI")
 defer win.Destroy()

 // activate webCamera
 webCamera = opencv.NewCameraCapture(opencv.CV_CAP_ANY) // autodetect

 if webCamera == nil {
 panic("Unable to open camera")
 }

 defer webCamera.Release()

 // get some data from camera
 width = int(webCamera.GetProperty(opencv.CV_CAP_PROP_FRAME_WIDTH))
 height = int(webCamera.GetProperty(opencv.CV_CAP_PROP_FRAME_HEIGHT))

 fmt.Println("Camera width : ", width)
 fmt.Println("Camera height : ", height)

 // open up a new "pure" OpenCV window first
 go processFrameAndUpdate() // goroutine to update feed from camera

 // then our "floating" GTK toolbar
 gtk.Init(nil)
 window := gtk.NewWindow(gtk.WINDOW_TOPLEVEL)

 window.SetPosition(gtk.WIN_POS_CENTER)
 window.SetTitle("Golang-GTK-OpenCV-AppleBooth-Example!")
 window.SetIconName("gtk-dialog-info")
 window.Connect("destroy", func(ctx *glib.CallbackContext) {
 println("got destroy!", ctx.Data().(string))
 gtk.MainQuit()
 }, "Happy coding!")

 vbox := gtk.NewVBox(false, 1)

 //--------------------------------------------------------
 // GtkVPaned
 //--------------------------------------------------------
 vpaned := gtk.NewVPaned()
 vbox.Add(vpaned)

 //--------------------------------------------------------
 // GtkFrame
 //--------------------------------------------------------

 frame1 := gtk.NewFrame("Adjust X & Y co-ordinates to find top-left, top-right, bottom-left & bottom-right :")
 framebox1 := gtk.NewVBox(false, 1)
 frame1.Add(framebox1)


 //--------------------------------------------------------
 // GtkScale
 //--------------------------------------------------------
 scaleXHBox := gtk.NewHBox(false, 1)

 scaleX := gtk.NewHScaleWithRange(0, float64(width), 1)
 scaleX.Connect("value-changed", func() {
 //println("scale:", int(scale.GetValue()))
 sliderPosX = int(scaleX.GetValue())
 statusbar.Push(statusbar.GetContextId("go-gtk"), "X : "+strconv.Itoa(sliderPosX)+" Y : "+strconv.Itoa(sliderPosY))
 })
 scaleXHBox.Add(scaleX)
 framebox1.PackStart(scaleXHBox, false, false, 0)

 scaleYHBox := gtk.NewHBox(false, 1)

 scaleY := gtk.NewHScaleWithRange(0, float64(height), 1)
 scaleY.Connect("value-changed", func() {
 //println("scale:", int(scale.GetValue()))
 sliderPosY = int(scaleY.GetValue())
 statusbar.Push(statusbar.GetContextId("go-gtk"), "X : "+strconv.Itoa(sliderPosX)+" Y : "+strconv.Itoa(sliderPosY))
 })
 scaleYHBox.Add(scaleY)
 framebox1.PackStart(scaleYHBox, false, false, 0)

 vpaned.Pack1(frame1, false, false)

 //--------------------------------------------------------
 // GtkHBox
 //--------------------------------------------------------
 buttons := gtk.NewHBox(false, 1)

 //--------------------------------------------------------
 // GtkButton
 //--------------------------------------------------------

 quitButton := gtk.NewButtonWithLabel("Quit")
 quitButton.Clicked(func() {
 gtk.MainQuit()
 })

 buttons.Add(quitButton)
 framebox1.PackStart(buttons, false, false, 0)


 //--------------------------------------------------------
 // GtkVSeparator
 //--------------------------------------------------------
 vsep := gtk.NewVSeparator()
 framebox1.PackStart(vsep, false, false, 0)

 statusbar = gtk.NewStatusbar()
 //context_id := statusbar.GetContextId("go-gtk")

 //--------------------------------------------------------
 // GtkStatusbar
 //--------------------------------------------------------
 framebox1.PackStart(statusbar, false, false, 0)

 //--------------------------------------------------------
 // Event
 //--------------------------------------------------------
 window.Add(vbox)
 window.SetSizeRequest(600, 130)
 window.ShowAll()

 gtk.Main()

 }

References:

https://www.socketloop.com/tutorials/golang-another-camera-capture-gui-application-with-gtk-and-opencv

https://github.com/lazywei/go-opencv/blob/8d3d2da557334be2bd648ab77202ee107fe942b0/opencv/cxcore_test.go

https://godoc.org/github.com/lazywei/go-opencv/opencv#Point

https://www.socketloop.com/tutorials/golang-get-current-time

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  See also : Golang : Detect number of faces or vehicles in a photo



Tags : golang GUI openCV putText color time

By Adam Ng

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