anchor.diff:    (write-byte (plus 8 (mul 3 cn)) out-stream)
     (write-byte 8 out-stream) ;sample precision
     (write-byte (ash maxY -8) out-stream) ;max height
  -  (write-byte (logand maxY #xff) out-stream) 
  +  (write-byte (logand maxY #xff) out-stream)
     (write-byte (ash maxX -8) out-stream) ;max width
     (write-byte (logand maxX #xff) out-stream)
     (write-byte cn out-stream) ;number of components
  
positive.code:     (write-marker +M_EOI+ out-stream)))
  
  (defun encode-image (filename image ncomp h w &rest args)
    (with-open-file (out-stream filename 
                                :direction :output
                                :element-type 'unsigned-byte
                                :if-exists :supersede)
  
negative.code:                  (if (= k 63)
                       (return zz)
                     (incf k))))))
  
  ;;; Decodes DC value
  (defun decode-dc (maxcode mincode valptr huffval nextbit s)
    "Decodes DC value"
  