gistfile1.lisp

;; retrieve raw image data

(multiple-value-bind (background-bitmap background-data)
    (cocoa-get-image-bytes ns-background)
  (multiple-value-bind (image-bitmap image-data)
      (cocoa-get-image-bytes ns-image)
    (multiple-value-bind (mask-bitmap mask-data)
        (cocoa-get-image-bytes ns-mask)

      (cocoa-blend background-data 
                   image-data 
                   mask-data 
                   offset size)

      (objc:invoke ns-background
                   "removeRepresentation:"
                   (objc:invoke 
                    (objc:invoke ns-background "representations")
                    "objectAtIndex:" 0))
  
      (objc:invoke ns-background 
                   "addRepresentation:" 
                   background-bitmap)