Convert writer_png to C++; add Writer class; add PNGWriter class

src/SConscript

@@ -9,6 +9,7 @@ files = Split("""
     object.cc
     object_sphere.cc
     scene.cc
+    writer_png.cc
 """)
 
 lib = env.Library('charles', files)

src/writer.h

@@ -0,0 +1,21 @@
+/* writer.h
+ *
+ * Writers handle the interface between (mostly) C libraries to write various image formats and the rest of Charles.
+ *
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+#ifndef __WRITER_H__
+#define __WRITER_H__
+
+#include <string>
+#include "scene.h"
+
+
+class Writer
+{
+public:
+    virtual int write_scene(const Scene &scene, const std::string &filename) = 0;
+};
+
+#endif

src/writer_png.cc

@@ -5,33 +5,37 @@
  * Eryn Wells <eryn@erynwells.me>
  */
 
+#include <csetjmp>
+#include <cstdlib>
+#include <string>
 
-#include <setjmp.h>
-#include <stdlib.h>
-
-#include <png.h>
-
+#include "scene.h"
 #include "writer_png.h"
 
+extern "C" {
+#include <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 --
+ * PNGWriter::write_scene --
  *
- * Write the given scene to file in PNG format.
+ * Write the given scene to a file in PNG format.
  */
 int
-write_scene_png(Scene *scene, FILE *file)
+PNGWriter::write_scene(const Scene &scene, const std::string &filename)
 {
-    if (!scene->is_rendered) {
+    if (!scene.is_rendered()) {
         return -1;
     }
 
+    FILE *file = fopen(filename.c_str(), "wb");
     if (!file) {
-        return -2;
+        return -1;
     }
 
     // Set up the PNG data structures. libpng requires two: a PNG object and an info object.
@@ -39,7 +43,6 @@ write_scene_png(Scene *scene, FILE *file)
     if (!png) {
         return -3;
     }
-
     png_infop png_info = png_create_info_struct(png);
     if (!png_info) {
         return -4;
@@ -59,7 +62,7 @@ write_scene_png(Scene *scene, FILE *file)
      *   - No compression
      */
     png_set_IHDR(png, png_info,
-                 scene->width, scene->height,
+                 scene.get_width(), scene.get_height(),
                  8, PNG_COLOR_TYPE_RGB,
                  PNG_INTERLACE_NONE,
                  PNG_COMPRESSION_TYPE_DEFAULT,
@@ -72,21 +75,24 @@ write_scene_png(Scene *scene, FILE *file)
     png_write_info(png, png_info);
 
     // Write it!
+    const Color *pixels = scene.get_pixels();
+    png_byte *row = NULL;
     int nbytes = 0;
-    for (int y = 0; y < scene->height; y++) {
-        png_byte *row = malloc(png_sizeof(png_byte) * scene->width * 3);
+    for (int y = 0; y < scene.get_height(); y++) {
+        row = new png_byte[scene.get_width() * 3];
         if (row == NULL) {
             // TODO: DANGER! WILL ROBINSON!
         }
-        for (int x = 0; x < scene->width; x++) {
-            row[x*3+0] = scene->pixels[y * scene->width + x].red;
-            row[x*3+1] = scene->pixels[y * scene->width + x].green;
-            row[x*3+2] = scene->pixels[y * scene->width + x].blue;
+        for (int x = 0; x < scene.get_width(); x++) {
+            Color c = pixels[y * scene.get_width() + x];
+            row[x*3+0] = 0xff * c.red;
+            row[x*3+1] = 0xff * c.green;
+            row[x*3+2] = 0xff * c.blue;
             nbytes += 3;
 
         }
         png_write_row(png, row);
-        free(row);
+        delete[] row;
     }
 
     // Clean up!
@@ -103,6 +109,7 @@ write_scene_png(Scene *scene, FILE *file)
  *
  * Called by libpng when it encounters an error.
  */
+
 /* static */ void
 png_user_error(png_structp png,
                png_const_charp msg)
@@ -116,6 +123,7 @@ png_user_error(png_structp png,
  *
  * Called by libpng when it encounters an warning.
  */
+
 /* static */ void
 png_user_warning(png_structp png,
                  png_const_charp msg)

src/writer_png.h

@@ -5,15 +5,17 @@
  * Eryn Wells <eryn@erynwells.me>
  */
 
+#ifndef __WRITER_PNG_H__
+#define __WRITER_PNG_H__
 
-#ifndef __WRITER_PNG_H
-#define __WRITER_PNG_H
-
-#include <stdio.h>
-#include "scene.h"
+#include "writer.h"
 
 
-int write_scene_png(Scene *scene, FILE *file);
-
+class PNGWriter
+    : public Writer
+{
+public:
+    int write_scene(const Scene &scene, const std::string &filename);
+};
 
 #endif