Canvas implementation and add build of LodePNG

tests/canvas_test.cpp

@@ -0,0 +1,53 @@
+/*
+ *  DoRayMe - a quick and dirty Raytracer
+ *  Canvas unit tests
+ *
+ *  Created by Manoël Trapier
+ *  Copyright (c) 2020 986-Studio.
+ *
+ */
+#include <colour.h>
+#include <canvas.h>
+#include <math.h>
+#include <gtest/gtest.h>
+
+TEST(CanvasTest, Creating_a_canvas)
+{
+    Canvas c = Canvas(10, 20);
+    int x, y;
+    ASSERT_EQ(c.width, 10);
+    ASSERT_EQ(c.height, 20);
+    for(y = 0; y < 20; y++)
+    {
+        for(x = 0; x < 10; x++)
+        {
+            ASSERT_EQ(c.get_pixel(x, y), Colour(0, 0, 0));
+        }
+    }
+}
+
+TEST(CanvasTest, Test_Writing_pixels_to_a_canvas_Test)
+{
+    Canvas c = Canvas(10, 20);
+    Colour red = Colour(1, 0, 0);
+
+    c.put_pixel(2, 3, red);
+
+    ASSERT_EQ(c.get_pixel(2, 3), red);
+
+}
+
+TEST(CanvasTest, Save_a_PNG_file)
+{
+    Canvas c = Canvas(5, 3);
+    Colour c1 = Colour(1.5, 0, 0);
+    Colour c2 = Colour(0, 0.5, 0);
+    Colour c3 = Colour(-0.5, 0, 1);
+
+    c.put_pixel(0, 0, c1);
+    c.put_pixel(2, 1, c2);
+    c.put_pixel(4, 2, c3);
+
+    ASSERT_TRUE(c.SaveAsPNG("Save_a_PNG_file.png"));
+
+}