code: func (c Config) computedCropArea(bounds image.Rectangle, size image.Point) (r image.Rectangle) {
  	min := bounds.Min
  	switch c.Mode {
  	case Centered:
  		rMin := c.centeredMin(bounds)
  		r = image.Rect(rMin.X-size.X/2, rMin.Y-size.Y/2, rMin.X-size.X/2+size.X, rMin.Y-size.Y/2+size.Y)
  	default: // TopLeft
  		rMin := image.Point{min.X + c.Anchor.X, min.Y + c.Anchor.Y}
  		r = image.Rect(rMin.X, rMin.Y, rMin.X+size.X, rMin.Y+size.Y)
  	}
  	return
  }
docs: // computedCropArea retrieve the theorical crop area.
  // It is defined by Height, Width, Mode and