code: func (c Config) computeSize(bounds image.Rectangle, ratio image.Point) (p image.Point) {
  	if c.Options&Ratio == Ratio {
  		// Ratio option is on, so we take the biggest size available that fit the given ratio.
  		if float64(ratio.X)/float64(bounds.Dx()) > float64(ratio.Y)/float64(bounds.Dy()) {
  			p = image.Point{bounds.Dx(), (bounds.Dx() / ratio.X) * ratio.Y}
  		} else {
  			p = image.Point{(bounds.Dy() / ratio.Y) * ratio.X, bounds.Dy()}
  		}
  	} else {
  		p = image.Point{ratio.X, ratio.Y}
  	}
  	return
  }
docs: // computeSize retrieve the effective size of the cropped image.
  // It is defined by Height, Width, and Ratio option.