grayscale.go

func greyScale(pixels *[][]color.Color)  {
  ppixels := *pixels
  xLen:=len(ppixels)
  yLen := len(ppixels[0])
  //create new image
  newImage:=make([][]color.Color, xLen)
  for i:=0;i<len(newImage);i++{
     newImage[i] = make([]color.Color,yLen)
  }
  //idea is processing pixels in parallel
  wg := sync.WaitGroup{}
  for x:=0;x<xLen;x++{
     for y:=0;y<yLen; y++{
        wg.Add(1)
        go func(x,y int) {
           pixel :=ppixels[x][y]
           originalColor,ok := color.RGBAModel.Convert(pixel).(color.RGBA)
           if !ok{
              fmt.Println("type conversion went wrong")
           }
           grey := uint8(float64(originalColor.R)*0.21 + float64(originalColor.G)*0.72 + float64(originalColor.B)*0.07)
           col :=color.RGBA{
              grey,
              grey,
              grey,
              originalColor.A,
           }
           newImage[x][y] = col
           wg.Done()
        }(x,y)

     }
  }
  wg.Wait()
  *pixels = newImage
}