[OpenCV] Chapter02-08 Computing image histogram

Computing image histogram

Source Code

package main

import (
 "fmt"
 "gocv.io/x/gocv"
 "gonum.org/v1/plot"
 "gonum.org/v1/plot/plotter"
 "gonum.org/v1/plot/vg"
 "log"
)

func main() {
 imageFilePath := "../../data/Lena.png"
 originalMat := gocv.IMRead(imageFilePath, gocv.IMReadGrayScale)
 if originalMat.Empty() {
  log.Panic("Can not read image: " + imageFilePath)
  return
 }

 windowForGrey := gocv.NewWindow("Original grey")
 defer windowForGrey.Close()
 windowForGrey.IMShow(originalMat)

 originalImage := originalMat.ToBytes()

 v := make(plotter.Values, len(originalImage))
 for i := 0; i < len(v); i++ {
  v[i] = float64(originalImage[i])
 }

 plot, err := plot.New()
 if err != nil {
  log.Println("Can not create plot", err)
  return
 }

 plot.Title.Text = fmt.Sprintf("Histogram of a %s", "Grey Image")

 histogram, err := plotter.NewHist(v, len(v))
 if err != nil {
  log.Panic("Can not create histogram", err)
  return
 }

 histogram.Normalize(1)

 plot.Add(histogram)

 if err := plot.Save(4*vg.Inch, 4*vg.Inch, "histogram_for_image.png"); err != nil {
  log.Panic(err)
  return
 }

 // wait
 for {
  key := gocv.WaitKey(3)
  if key == 27 {
   log.Println("Pressed ESC")
   break
  }
 }
}

Execute Result