Golang : Add text to image and get OpenCV's X, Y co-ordinates example
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).
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://godoc.org/github.com/lazywei/go-opencv/opencv#Point
https://www.socketloop.com/tutorials/golang-get-current-time
See also : Golang : Detect number of faces or vehicles in a photo
By Adam Ng
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