Golang : Select region of interest with mouse click and crop from image
Just a short Golang OpenCV program that allows the user to select a region of interest on an image with mouse click. The selected rectangular region of interest will be cropped and displayed on another window.
An example screen shot:
Here you go!
package main
import (
"fmt"
"github.com/lazywei/go-opencv/opencv"
"math"
"os"
)
var (
win = new(opencv.Window)
cropWindow = new(opencv.Window)
corner1 = new(opencv.Point)
corner2 = new(opencv.Point)
pt = new(opencv.Point)
leftDown = false
leftUp = false
image = new(opencv.IplImage)
redColor = opencv.NewScalar(0, 0, 255, 255) // (blue, green, red, alpha)
)
func mouseCallBack(event, x, y, flags int, param ...interface{}) {
// if mouse left button is pressed, record the positions and save to corner1
if event == opencv.CV_EVENT_LBUTTONDOWN {
leftDown = true
corner1.X = x
corner1.Y = y
fmt.Printf("Corner 1 : X=%d Y=%d\n", corner1.X, corner1.Y)
}
if event == opencv.CV_EVENT_LBUTTONUP {
leftUp = true
corner2.X = x
corner2.Y = y
fmt.Printf("Corner 2 : X=%d Y=%d\n", corner2.X, corner2.Y)
}
// draw a red rectangle box when left mouse button is pressed and drag
if (leftDown == true) && (leftUp == false) {
pt.X = x
pt.Y = y
roiImage := image.Clone()
opencv.Rectangle(roiImage, *corner1, *pt, redColor, 1, 4, 0)
win.ShowImage(roiImage)
}
// crop image when both corners are populated
if (leftDown == true) && (leftUp == true) {
cropBoxWidth := math.Abs(float64(corner1.X) - float64(corner2.X))
cropBoxHeight := math.Abs(float64(corner1.Y) - float64(corner2.Y))
cropBoxX := math.Min(float64(corner1.X), float64(corner2.X))
cropBoxY := math.Min(float64(corner1.Y), float64(corner2.Y))
fmt.Println("X : ", cropBoxX)
fmt.Println("Y : ", cropBoxY)
fmt.Println("Width : ", cropBoxWidth)
fmt.Println("Height : ", cropBoxHeight)
// sanity check on input parameters
// ignore if user just click on the image
// i.e width and height equal zero
if (cropBoxWidth != 0) && (cropBoxHeight != 0) {
cropImage := opencv.Crop(image, int(cropBoxX), int(cropBoxY), int(cropBoxWidth), int(cropBoxHeight))
cropWindow.Resize(int(cropBoxWidth), int(cropBoxHeight))
cropWindow.ShowImage(cropImage)
cropImage.Release()
}
leftDown = false
leftUp = false
}
}
func main() {
if len(os.Args) != 2 {
fmt.Printf("Usage : %s <image filename>\n", os.Args[0])
os.Exit(0)
}
imageFileName := os.Args[1]
fmt.Println("Loading image from ", imageFileName)
fmt.Println("Press ESC key to quit")
image = opencv.LoadImage(imageFileName)
if image == nil {
panic("LoadImage failed")
}
defer image.Release()
win = opencv.NewWindow("Select and crop region of interest")
win.Move(100, 100) // so that this window does not hide the crop window
defer win.Destroy()
cropWindow = opencv.NewWindow("Crop region of interest")
defer cropWindow.Destroy()
win.SetMouseCallback(mouseCallBack)
win.ShowImage(image)
for {
key := opencv.WaitKey(20)
if key == 27 {
os.Exit(0)
}
}
os.Exit(0)
}
References:
https://socketloop.com/tutorials/golang-put-utf8-text-on-opencv-video-capture-image-frame
https://github.com/lazywei/go-opencv/blob/master/samples/crop.go
See also : Golang : Put UTF8 text on OpenCV video capture image frame
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+8.8k PHP : Get coordinates latitude/longitude from string
+5.3k Golang : Map within a map example
+6.4k Golang : Get YouTube playlist
+28.1k Golang : Get time.Duration in year, month, week or day
+7.8k Golang : Capture text return from exec function example
+10.4k Golang : Surveillance with web camera and OpenCV
+7.7k Golang : Accept any number of function arguments with three dots(...)
+2.8k Java : Random alphabets, alpha-numeric or numbers only string generator
+23.1k Golang : Time slice or date sort and reverse sort example
+11k Golang : Send data to /dev/null a.k.a blackhole with ioutil.Discard
+6.6k SSL : How to check if current certificate is sha1 or sha2 from command line