code: func Fill(img image.Image, width, height int, anchor Anchor, filter ResampleFilter) *image.NRGBA {
  	dstW, dstH := width, height
  
  	if dstW <= 0 || dstH <= 0 {
  		return &image.NRGBA{}
  	}
  
  	srcBounds := img.Bounds()
  	srcW := srcBounds.Dx()
  	srcH := srcBounds.Dy()
  
  	if srcW <= 0 || srcH <= 0 {
  		return &image.NRGBA{}
  	}
  
  	if srcW == dstW && srcH == dstH {
  		return Clone(img)
  	}
  
  	if srcW >= 100 && srcH >= 100 {
  		return cropAndResize(img, dstW, dstH, anchor, filter)
  	}
  	return resizeAndCrop(img, dstW, dstH, anchor, filter)
  }
docs: // Fill creates an image with the specified dimensions and fills it with the scaled source image.
  // To achieve the correct aspect ratio without stretching, the source image will be cropped.
  //
  // Example:
  //
  //	dstImage := imaging.Fill(srcImage, 800, 600, imaging.Center, imaging.Lanczos)
  //