Output images as png.

.gitignore

@@ -1,3 +1,4 @@
 *.o
 wtracer
 *.ppm
+*.png

Makefile

@@ -2,16 +2,16 @@ CXX = g++
 
 CXXFLAGS  = -std=c++14 -Wall -Wextra -Wno-unused-parameter -march=native -Ofast -fopenmp -flto
 
-DEPS = util.h vec3.h color.h ray.h camera.h hittable.h hittable_list.h sphere.h material.h
-OBJ = wtracer.o material.o vec3.o
+DEPS = util.h vec3.h color.h ray.h camera.h hittable.h hittable_list.h sphere.h material.h lodepng.h
+OBJ = wtracer.o material.o vec3.o lodepng.o
 
 TARGET = wtracer
 
 all: $(TARGET) run
 
 run: $(TARGET)
-	time -f '%E elapsed' ./wtracer > image.ppm
-	eog image.ppm
+	time -f '%E elapsed' ./wtracer
+	eog image.png
 
 %.o: %.cpp $(DEPS)
 	$(CXX) $(CXXFLAGS) -c -o $@ $<

color.h

@@ -1,8 +1,10 @@
 #ifndef COLOR_H
 #define COLOR_H
 
+#include <vector>
 #include <iostream>
 #include <cmath>
+#include <cstddef>
 
 #include "vec3.h"
 #include "util.h"
@@ -22,4 +24,19 @@ void write_color(std::ostream &out, Color pixel_color, int sample_per_pixel) {
         << static_cast<int>(256 * clamp(b, 0.0, 0.999)) << "\n";
 }
 
+void write_color_vec(std::vector<unsigned char>& vec, std::size_t i, Color pixel_color, int sample_per_pixel) {
+    auto r = pixel_color.x();
+    auto g = pixel_color.y();
+    auto b = pixel_color.z();
+
+    auto scale = 1.0 / sample_per_pixel;
+    r = std::sqrt(scale * r);
+    g = std::sqrt(scale * g);
+    b = std::sqrt(scale * b);
+
+    vec[i+0] = static_cast<unsigned char>(256 * clamp(r, 0.0, 0.999));
+    vec[i+1] = static_cast<unsigned char>(256 * clamp(g, 0.0, 0.999));
+    vec[i+2] = static_cast<unsigned char>(256 * clamp(b, 0.0, 0.999));
+}
+
 #endif // COLOR_H

wtracer.cpp

@@ -1,11 +1,14 @@
 #include <iostream>
+#include <iomanip>
 #include <memory>
 
+#define LODEPNG_NO_COMPILE_DECODER
+#include "lodepng.h"
+
 #include "color.h"
 #include "vec3.h"
 #include "ray.h"
 #include "util.h"
-
 #include "hittable_list.h"
 #include "sphere.h"
 #include "camera.h"
@@ -95,29 +98,37 @@ int main() {
 
     Camera cam(lookfrom, lookat, vup, 20, aspect_ratio, aperture, dist_to_focus);
 
-    auto image = std::make_unique<Color[]>(image_height*image_width);
+    std::vector<Color> image(image_width * image_height);
 
-    for (int j = image_height - 1; j >= 0; --j) {
-        std::cerr << "\rScanlines remaining: " << j << " " << std::flush;
+    for (int i = image_height-1; i>=0; --i) {
+        std::cerr << "\rScanline remaining: " << std::setw(4) << i << std::flush;
         #pragma omp parallel for
-        for (int i = 0; i < image_width; ++i) {
+        for (int j = 0; j<image_width; ++j) {
             Color pixel_color(0, 0, 0);
             for (int s = 0; s<samples_per_pixel; ++s) {
-                auto u = double(i + random_double(-0.5, 0.5)) / (image_width - 1);
-                auto v = double(j + random_double(-0.5, 0.5)) / (image_height - 1);
+                auto u = double(j + random_double(-0.5, 0.5)) / (image_width - 1);
+                auto v = double(i + random_double(-0.5, 0.5)) / (image_height - 1);
                 Ray r = cam.get_ray(u, v);
                 pixel_color += ray_color(r, world, max_depth);
             }
-            image[i*image_height+j] = pixel_color;
+            image.at(i*image_width+j) = pixel_color;
         }
     }
-    std::cerr << "\nWriting file.\n";
 
-    std::cout << "P3\n" << image_width << " " << image_height << "\n255\n";
-    for (int j = image_height - 1; j >= 0; --j) {
-        for (int i = 0; i < image_width; ++i) {
-            write_color(std::cout, image[i*image_height+j], samples_per_pixel);
+    std::cerr << "\nAssembling image.\n";
+
+    std::vector<unsigned char> img_lode(image_width * image_height * 3);
+    for (int i = 0; i<image_height; ++i) {
+        for (int j = 0; j<image_width; ++j) {
+            write_color_vec(img_lode, i*image_width*3+j*3, image.at((image_height-1-i)*image_width+j), samples_per_pixel);
         }
     }
+    std::cerr << "Writing file \"image.png\".\n";
+
+    unsigned error = lodepng::encode("image.png", img_lode, image_width, image_height, LCT_RGB);
+
+    if (error)
+        std::cerr << "lodepng encoder error " << error << ": "<< lodepng_error_text(error) << std::endl;
+
     std::cerr << "Done.\n";
 }