have the pict datatype support conversion to PNG, EPS, or PDF bytes

collects/file/scribblings/convertible.scrbl

@@ -23,6 +23,7 @@ should be considered standard:
  @item{@scheme['gif-bytes] --- a byte string containing a GIF image encoding}
  @item{@scheme['png-bytes] --- a byte string containing a PNG image encoding}
  @item{@scheme['ps-bytes] --- a byte string containing a PostScript document}
+ @item{@scheme['eps-bytes] --- a byte string containing an Encapsulated PostScript document}
  @item{@scheme['pdf-bytes] --- a byte string containing a PDF document}
 ]
 

collects/scribblings/slideshow/picts.scrbl

@@ -65,6 +65,10 @@ picts. The functions @racket[pict-width], @racket[pict-height],
 @racket[pict-descent], and @racket[pict-ascent] extract bounding-box
 information from a pict.
 
+A pict is a convertible datatype through the @racket[file/convertible]
+protocol. Supported conversions include @racket['png-bytes],
+@racket['eps-bytes], and @racket['pdf-bytes].
+
 
 @defstruct[pict ([draw any/c]
                  [width real?]

collects/texpict/private/common-sig.rkt

@@ -123,7 +123,8 @@
   (provide texpict-common-setup^)
   (define-signature texpict-common-setup^
     (connect
-     ~connect))
+     ~connect
+     convert-pict))
 
   (provide texpict-internal^)
   (define-signature texpict-internal^

collects/texpict/private/common-unit.rkt

@@ -2,7 +2,8 @@
 
   (require racket/draw
            racket/class
-           racket/list)
+           racket/list
+           file/convertible)
   
   (require "common-sig.ss")
 
@@ -20,7 +21,9 @@
 			   children   ; list of child records
 			   panbox     ; panorama box, computed on demand
                            last)      ; a descendent for the bottom-right
-        #:mutable)
+        #:mutable
+        #:property prop:convertible (lambda (v mode default)
+                                      (convert-pict v mode default)))
       (define-struct child (pict dx dy sx sy))
       (define-struct bbox (x1 y1 x2 y2 ay dy))
 

collects/texpict/private/mrpict-extra.rkt

@@ -442,3 +442,30 @@
 
       (define (draw-pict p dc dx dy)
 	((make-pict-drawer p) dc dx dy))
+
+
+      (define (convert-pict p format default)
+        (case format
+          [(png-bytes)
+           (let* ([bm (make-bitmap (max 1 (pict-width p)) (max 1 (pict-height p)))]
+                  [dc (make-object bitmap-dc% bm)])
+             (draw-pict p dc 0 0)
+             (send dc set-bitmap #f)
+             (let ([s (open-output-bytes)])
+               (send bm save-file s 'png)
+               (get-output-bytes s)))]
+          [(eps-bytes pdf-bytes)
+           (let ([s (open-output-bytes)])
+             (let ([dc (new (if (eq? format 'eps-bytes) post-script-dc% pdf-dc%)
+                            [interactive #f]
+                            [as-eps #t]
+                            [output s])])
+               (send dc start-doc "pict")
+               (send dc start-page)
+               (draw-pict p dc 0 0)
+               (send dc end-page)
+               (send dc end-doc))
+             (get-output-bytes s))]
+          [else default]))
+
+             

collects/texpict/private/texpict-extra.rkt

@@ -466,3 +466,5 @@
 		  [else (error 'pict->string "bad tag: ~s" tag)])))))
 
       (define pict->commands pict->command-list)
+
+      (define (convert-pict p v d) d)