   bitmap.pixels = new Pixel[bitmap.width * bitmap.height];
   cudaMemcpy(bitmap.pixels, devicePixels, sizeof(Pixel) * bitmap.width * bitmap.height, cudaMemcpyDeviceToHost);
 
-  save_png_to_file(&bitmap, "fractal.png");
+  save_png_to_file(&bitmap, filename);
 
   cudaFree(devicePixels);
   cudaFree(devBitmap);

#include <iostream>
#include <cmath>
#include <thrust/complex.h>

using thrust::complex;
using thrust::exp;
using thrust::norm;

  //   result[i] = iteration(c[i]);
  // }

  double lowerX = -2, upperX = 2;
  double lowerY = -2, upperY = 2;

  int x, y;
