code: func CropAnchor(img image.Image, width, height int, anchor Anchor) *image.NRGBA {
  	srcBounds := img.Bounds()
  	pt := anchorPt(srcBounds, width, height, anchor)
  	r := image.Rect(0, 0, width, height).Add(pt)
  	b := srcBounds.Intersect(r)
  	return Crop(img, b)
  }
docs: // CropAnchor cuts out a rectangular region with the specified size
  // from the image using the specified anchor point and returns the cropped image.