From f81ebbfbf79f929e98d54e5e861f43a813e9d20b Mon Sep 17 00:00:00 2001
From: John Clements <clements@racket-lang.org>
Date: Wed, 28 Apr 2010 11:48:07 -0700
Subject: [PATCH] Exported save-image per Matthias' request, wrote conservative
 documentation

---
 collects/2htdp/image.rkt                      |  2 ++
 .../teachpack/2htdp/scribblings/image-gen.rkt |  3 +--
 .../teachpack/2htdp/scribblings/image.scrbl   | 21 ++++++++++++++++++-
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/collects/2htdp/image.rkt b/collects/2htdp/image.rkt
index d2f5adc208..f52e490070 100644
--- a/collects/2htdp/image.rkt
+++ b/collects/2htdp/image.rkt
@@ -115,6 +115,8 @@ and they all have good sample contracts. (It is amazing what we can do with kids
          
          make-color
          make-pen
+         
+         save-image
          )
 
 (provide bitmap)
diff --git a/collects/teachpack/2htdp/scribblings/image-gen.rkt b/collects/teachpack/2htdp/scribblings/image-gen.rkt
index 2421d6c221..36b5fd00bb 100644
--- a/collects/teachpack/2htdp/scribblings/image-gen.rkt
+++ b/collects/teachpack/2htdp/scribblings/image-gen.rkt
@@ -5,8 +5,7 @@
 
 (require 2htdp/image
          lang/posn
-         scheme/runtime-path
-         (only-in 2htdp/private/image-more save-image))
+         scheme/runtime-path)
 
 (define-runtime-path image.scrbl "image.scrbl")
 (define-runtime-path img "img")
diff --git a/collects/teachpack/2htdp/scribblings/image.scrbl b/collects/teachpack/2htdp/scribblings/image.scrbl
index 1ff710b855..830879cb24 100644
--- a/collects/teachpack/2htdp/scribblings/image.scrbl
+++ b/collects/teachpack/2htdp/scribblings/image.scrbl
@@ -4,7 +4,8 @@
                      2htdp/image
                      (except-in lang/htdp-beginner make-posn posn? posn-x posn-y image?)
                      lang/posn
-                     scheme/gui/base)
+                     scheme/gui/base
+                     (only-in scheme/base path-string?))
           lang/posn
           "shared.ss"
           "image-util.ss"
@@ -1044,3 +1045,21 @@ pixel wide pen draws the pixels above and below the line, but each with
 a color that is half of the intensity of the given color. Using a
 @scheme[pen] with with two, colors the pixels above and below the line
 with the full intensity. 
+
+
+@;-----------------------------------------------------------------------------
+@section{Exporting Images to Disk}
+
+In order to use an image as an input to another program (Photoshop, e.g., or 
+a web browser), it is necessary to represent it in a format that these programs
+can understand. The @scheme[save-image] function provides this functionality, 
+writing an image to disk using the @tt{PNG} format. Since this
+format represents an image using a set of pixel values, an image written to disk
+generally contains less information than the image that was written, and cannot be scaled
+or manipulated as cleanly (by any image program).
+
+@defproc[(save-image [image image?] [filename path-string?]) boolean?]{
+ writes an image to the path specified by @scheme[filename], using the
+ @tt{PNG} format.}
+
+