code: func (im *Image) SetBGRA(x, y int, c BGRA) {
  	if !(image.Point{x, y}.In(im.Rect)) {
  		return
  	}
  
  	i := im.PixOffset(x, y)
  	im.Pix[i] = c.B
  	im.Pix[i+1] = c.G
  	im.Pix[i+2] = c.R
  	im.Pix[i+3] = c.A
  }
docs: // SetBGRA is like set, but without the type assertion.