init: HW2

part2/common/ppm.cpp

@@ -0,0 +1,38 @@
+#include <algorithm>
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+
+void write_ppm_image(int *data, int width, int height, const char *filename, int max_iterations)
+{
+    FILE *fp = fopen(filename, "wb");
+    if (!fp)
+    {
+        perror("fopen() failed");
+        exit(EXIT_FAILURE);
+    }
+
+    // write ppm header
+    fprintf(fp, "P6\n");
+    fprintf(fp, "%d %d\n", width, height);
+    fprintf(fp, "255\n");
+
+    for (int i = 0; i < width * height; ++i)
+    {
+
+        // Clamp iteration count for this pixel, then scale the value
+        // to 0-1 range.  Raise resulting value to a power (<1) to
+        // increase brightness of low iteration count
+        // pixels. a.k.a. Make things look cooler.
+
+        float mapped = std::pow(
+            std::min(static_cast<float>(max_iterations), static_cast<float>(data[i])) / 256.f, .5f);
+
+        // convert back into 0-255 range, 8-bit channels
+        unsigned char result = static_cast<unsigned char>(255.f * mapped);
+        for (int j = 0; j < 3; ++j)
+            fputc(result, fp);
+    }
+    fclose(fp);
+    printf("Wrote image file %s\n", filename);
+}