Reading bitmaps from files
          Bitmaps can be read from files by sending the readBitmapFile:widthReturn:heightReturn:bitmapReturn:xHotReturn:yHotReturn: message to any CgDrawable. Parameters passed to the method include the file name and ReturnParameter objects for the width, height, the actual bitmap, and the x and y hot spot location. The value of any ReturnParameter object can be accessed by sending it the value message. 
          | error wReturn hReturn bReturn xReturn yReturn bitmap |
          error := CgWindow default
              readBitmapFile: 'brick'
              widthReturn: (wReturn := ReturnParameter new)
              heightReturn: (hReturn := ReturnParameter new)
              bitmapReturn: (bReturn := ReturnParameter new)
              xHotReturn: (xReturn := ReturnParameter new)
              yHotReturn: (yReturn := ReturnParameter new).
           
          error = 0
              ifTrue: [
                  Transcript cr; show: 'File read successful. ',
                      'Bitmap width: ', wReturn value printString,
                      ', height: ', hReturn value printString,
                      ', hotspot: ', (xReturn value @ yReturn value) printString.
                  bitmap := bReturn value.
                  bitmap freePixmap]
              ifFalse: [Transcript nextPutAll: 'File read error: ',
                error printString; cr].
         
        
          Last modified date: 01/29/2015