anchor.diff:          (strip-offsets (get-ifd-values ifd +strip-offsets-tag+))
           (rows-per-strip (get-ifd-value ifd +rows-per-strip-tag+))
           (strip-byte-counts (get-ifd-values ifd +strip-byte-counts-tag+))
  +        (predictor (get-ifd-value ifd +predictor-tag+))
           image-info
           (jpeg-tables (get-ifd-values ifd +jpeg-tables+)))
       (when jpeg-tables
  
positive.code:                                      image-width
                                       bits-per-sample
                                       compression))
           (make-instance 'tiff-image
                          :length image-length :width image-width
                          :bits-per-sample bits-per-sample
  
negative.code:                                      image-width
                                       bits-per-sample
                                       compression))
  
           (case predictor
             (#.+horizontal-differencing+
              (loop for i below image-length
                 do
                   (loop for j from 1 below image-width
                      do
                        (let ((offset (+ (* i image-width bytes-per-pixel)
                                         (* bytes-per-pixel j))))
                          (ecase *byte-order*
                            (:little-endian
                             (let ((old (+ (aref data (- offset 2))
                                           (ash (aref data (- offset 1)) 8))))
                               (let ((diff (+ (aref data offset)
                                              (ash (aref data (+ offset 1)) 8))))
                                 (let ((new (logand
                                             (+ old diff)
                                             #xffff)))
                                   (setf (aref data offset)
                                         (ldb (byte 8 0) new))
                                   (setf (aref data (1+ offset))
                                         (ldb (byte 8 8) new))))))
                            (:big-endian
                             (let ((old (+ (aref data (- offset 1))
                                           (ash (aref data (- offset 2)) 8))))
                               (let ((diff (+ (aref data (1+ offset))
                                              (ash (aref data offset) 8))))
                                 (let ((new (logand
                                             (+ old diff)
                                             #xffff)))
                                   (setf (aref data offset)
                                         (ldb (byte 8 8) new))
                                   (setf (aref data (1+ offset))
                                         (ldb (byte 8 0) new))))))))))))
  
           (make-instance 'tiff-image
                          :length image-length :width image-width
                          :bits-per-sample bits-per-sample
  