gistfile1.go

func checkImageDiff(img image.Image) bool {
  r, g, b, a := img.At(0, 0).RGBA()
  baseColor := [4]uint32{r, g, b, a}
  bounds := img.Bounds()
  results := make(chan bool)
  quit := make(chan bool)

  isSameColor := func(r, g, b, a uint32) bool {
    return baseColor[0] == r && baseColor[1] == g && baseColor[2] == b && baseColor[3] == a
  }

  for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
    go func() {
      matching := true

      for x := bounds.Min.X; x < bounds.Max.X; x++ {
        // Have to be renamed so that it can acquire
        // new memory address for each goroutine
        // and not all use the memory address shared
        // by the r, g, b, a closure
        nr, ng, nb, na := img.At(x, y).RGBA()

        if !isSameColor(nr, ng, nb, na) {
          matching = false
          break
        }

        select {
        case <-quit:
          return
        default:
          continue
        }
      }

      results <- matching
    }()
  }

  for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
    result := <-results
    if !result {
      quit <- true
      return false
    }
  }

  return true
}