From 0c8dc41d9f8da0dae8a171880efd9de3010328a1 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 16 Dec 2016 15:49:58 -0500
Subject: image: Add IMG_SavePNG binding.

---
 sdl2/bindings/image.scm | 3 +++
 sdl2/image.scm          | 9 ++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/sdl2/bindings/image.scm b/sdl2/bindings/image.scm
index cfdb31d..598c024 100644
--- a/sdl2/bindings/image.scm
+++ b/sdl2/bindings/image.scm
@@ -54,3 +54,6 @@ RETURN-TYPE and accept arguments of ARG-TYPES."
 
 (define-foreign img-load
   '* "IMG_Load" '(*))
+
+(define-foreign img-save-png
+  int "IMG_SavePNG" '(* *))
diff --git a/sdl2/image.scm b/sdl2/image.scm
index e741a04..ba0119b 100644
--- a/sdl2/image.scm
+++ b/sdl2/image.scm
@@ -29,7 +29,8 @@
   #:use-module ((sdl2 bindings image) #:prefix ffi:)
   #:export (image-init
             image-quit
-            load-image))
+            load-image
+            save-png))
 
 (define (image-init)
   "Initialize dynamically loaded image libraries."
@@ -49,3 +50,9 @@
     (if (null-pointer? ptr)
         (sdl-error "load-image" "failed to load image: ~a" file)
         ((@@ (sdl2 surface) wrap-surface) ptr))))
+
+(define (save-png surface file)
+  "Save SURFACE to FILE as a PNG formatted image."
+  (unless (zero? (ffi:img-save-png ((@@ (sdl2 surface) unwrap-surface) surface)
+                                   (string->pointer file)))
+    (sdl-error "save-png" "failed to save surface as PNG: ~a" file)))
-- 
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