anchor.diff:  ;;; returns NIL
   ;;;
   ;;; Additionaly, you may use more user-friendly version of encode-image: encode-wrapper.
  -;;; (encode-wrapper filename image ncomp h w &key quality)
  +;;; (encoding-wrapper filename image ncomp h w &key quality)
   ;;; All parameters have the same meaning as in encode-image, except quality.
   ;;; It is an integer value ranging 1 to 5 which specifies
   ;;; subjective quality of a resulting image.
  
positive.code: 
  (defun write-bits (bi ni s)
    (declare #.*optimize*
             (special *prev-length* *prev-byte*)
             (type fixnum bi ni *prev-length* *prev-byte*)
             (type stream s))
    (loop with lim fixnum = (if (> ni 8) 1 0)
          for i fixnum from lim downto 0 do
  
negative.code:     #(99 99 99 99 99 99 99 99)
      #(99 99 99 99 99 99 99 99)))
  
  (defconstant +q-luminance-hi+
    #(#(10 7 6 10 15 25 32 38)
      #(8 8 9 12 16 36 38 34)
      #(9 8 10 15 25 36 43 35)
  