C++ function for generating a series of Mandelbrot zoom PNG files.

mandel_zoomframe.cpp

static int GenerateZoomFrames(const char *outdir, int numframes, double xcenter, double ycenter, double zoom)
{
    try
    {
        // Create a video frame buffer with 720p resolution (1280x720).
        const int width  = 1280;
        const int height =  720;
        VideoFrame frame(width, height);

        const int limit = 16000;
        double multiplier = pow(zoom, 1.0 / (numframes - 1.0));
        double denom = 1.0;

        for (int f = 0; f < numframes; ++f)
        {
            // Calculate the real and imaginary range of values for each frame.
            // The zoom is exponential.
            // On the first frame, the scale is such that the smaller dimension (height) spans 4 units
            // from the bottom of the frame to the top.
            // On the last frame, the scale is that number of units divided by 'zoom'.
            double ver_span = 4.0 / denom;
            double hor_span = ver_span * (width - 1.0) / (height - 1.0);
            double ci_top = ycenter + ver_span/2.0;
            double ci_delta = ver_span / (height - 1.0);
            double cr_left = xcenter - hor_span/2.0;
            double cr_delta = hor_span / (width - 1.0);

            for (int x=0; x < width; ++x)
            {
                double cr = cr_left + x*cr_delta;
                for (int y=0; y < height; ++y)
                {
                    double ci = ci_top - y*ci_delta;
                    int count = Mandelbrot(cr, ci, limit);
                    PixelColor color = Palette(count, limit);
                    frame.SetPixel(x, y, color);
                }
            }

            // Create the output PNG filename in the format "outdir/frame_12345.png".
            char number[20];
            snprintf(number, sizeof(number), "%05d", f);
            std::string filename = std::string(outdir) + "/frame_" + number + ".png";

            // Save the video frame as a PNG file.
            int error = frame.SavePng(filename.c_str());
            if (error)
                return error;

            printf("Wrote %s\n", filename.c_str());

            // Increase the zoom magnification for the next frame.
            denom *= multiplier;
        }
        return 0;
    }
    catch (const char *message)
    {
        fprintf(stderr, "EXCEPTION: %s\n", message);
        return 1;
    }
}