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+;;; images.rkt -- support for image handline
+
+;; Copyright (C) 2012 Jose Antonio Ortega Ruiz
+
+;; This program is free software; you can redistribute it and/or
+;; modify it under the terms of the Modified BSD License. You should
+;; have received a copy of the license along with this program. If
+;; not, see <http://www.xfree86.org/3.3.6/COPYRIGHT2.html#5>.
+
+;; Authors: Michael Wilber, Jose Antonio Ortega Ruiz <jao@gnu.org>
+;; Start date: Sun Sep 2, 2012 18:54
+
+
+#lang racket/base
+
+(require racket/file file/convertible racket/pretty)
+(provide image-cache maybe-print-image maybe-write-image)
+
+(define image-cache
+  (let ([ensure-dir (lambda (dir)
+                      (if (path-string? dir)
+                          (begin (make-directory* dir)
+                                 (if (path? dir) (path->string dir) dir))
+                          (path->string (find-system-path 'temp-dir))))])
+    (make-parameter (ensure-dir #f) ensure-dir)))
+
+(define (save-tmpimage imgbytes)
+  ;; Save imgbytes to a new temporary file and return the filename
+  (define filename (make-temporary-file "geiser-img-~a.png" #f (image-cache)))
+  (with-output-to-file filename #:exists 'truncate
+                       (lambda () (display imgbytes)))
+  (format "#<Image: ~a>" filename))
+
+(define (maybe-save-image value)
+  (and (convertible? value)
+       ;; (The above could be problematic if a future version of racket
+       ;; suddenly decides it can "convert" strings to picts)
+       (save-tmpimage (convert value 'png-bytes))))
+
+(define (maybe-print-image value)
+  (cond [(maybe-save-image value) => (lambda (s) (printf "~a\n" s))]
+        [else (unless (void? value)
+                (pretty-print value))]))
+
+(define (maybe-write-image value)
+  (write (or (maybe-save-image value) value)))