Add writer_png module

src/SConscript

@@ -9,6 +9,7 @@ files = Split("""
     camera.c
     charles.c
     scene.c
+    writer_png.c
 """)
 
 prog = env.Program('charles', files)

src/writer_png.c

@@ -0,0 +1,80 @@
+/* writer_png.c
+ *
+ * Definition of the PNG writer.
+ *
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+
+#include <setjmp.h>
+
+#include <png.h>
+
+#include "writer_png.h"
+
+
+static void png_user_error(png_structp png, png_const_charp msg);
+static void png_user_warning(png_structp png, png_const_charp msg);
+
+
+/*
+ * write_scene_png --
+ *
+ * Write the given scene to file in PNG format.
+ */
+int
+write_scene_png(Scene *scene, FILE *file)
+{
+    if (!file) {
+        return -1;
+    }
+
+    // Set up the PNG data structures. libpng requires two: a PNG object and an info object.
+    png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, png_user_error, png_user_warning);
+    if (!png) {
+        return -2;
+    }
+
+    png_infop png_info = png_create_info_struct(png);
+    if (!png_info) {
+        return -3;
+    }
+
+    // Set up libpng error handling. If an error occurs, libpng will longjmp back here... (Wat.)
+    if (setjmp(png_jmpbuf(png))) {
+        png_destroy_write_struct(&png, &png_info);
+        return -4;
+    }
+
+    // Set up output.
+    png_init_io(png, file);
+
+    // TODO: Return number of bytes written.
+    return 0;
+}
+
+
+/*
+ * png_user_error --
+ *
+ * Called by libpng when it encounters an error.
+ */
+/* static */ void
+png_user_error(png_structp png,
+               png_const_charp msg)
+{
+
+}
+
+
+/*
+ * png_user_warning --
+ *
+ * Called by libpng when it encounters an warning.
+ */
+/* static */ void
+png_user_warning(png_structp png,
+                 png_const_charp msg)
+{
+
+}

src/writer_png.h

@@ -0,0 +1,19 @@
+/* writer_png.h
+ *
+ * Declaration of the PNG writer.
+ *
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+
+#ifndef __WRITER_PNG_H
+#define __WRITER_PNG_H
+
+#include <stdio.h>
+#include "scene.h"
+
+
+int write_scene_png(Scene *scene, FILE *file);
+
+
+#endif