Mandelbrot - Multi instead of Single color - c

Question

I have the following code from a class:
#include <stdio.h>
#include <math.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <gdk/gdk.h>
#include <gtk/gtk.h>
void destroy(void) {
gtk_main_quit();
}
static void
put_pixel (GdkPixbuf *pixbuf, int x, int y, guchar red, guchar green, guchar blue, guchar alpha);
typedef
struct complex{
double re;
double im;
} Complex;
int main(int argc, char** argv ){
gtk_init (&argc, &argv);
gint width = 256;
gint height = 256;
GdkColorspace cs = GDK_COLORSPACE_RGB;
GdkPixbuf* pixbuf = gdk_pixbuf_new( cs, 1, 8, width, height);
if (pixbuf == NULL ) {
fprintf( stderr, "Not able to create gdkimage object\n");
return -1;
}
/*
* Lower left and upper right corners of complex plane
*/
const Complex ll = {-2.5, -1.0};
const Complex ur = { 1.0, 1.0};
/*
* Resolution: Nx by Ny pixels in complex plane
*/
const int Nx = 256;
const int Ny = 256;
const double dx = (ur.re - ll.re)/(double)(Nx-1);
const double dy = (ur.im - ll.im)/(double)(Ny-1);
Complex z[Nx][Ny];
Complex c[Nx][Ny];
unsigned int pixel[Nx][Ny];
/*
* Number of iterations
*/
const int number_of_iterations = 1024;
/*
* Once the real or imaginary parts go beyond the max
* values, they have "escaped"
*/
const double Max = 4.0;
/*
* Initialize z and c
*/
printf("Initializing ... \n");
int i=0;
for (i=0; i<Nx; i++) {
int j=0;
for (j=0; j<Ny; j++) {
z[i][j].re = z[i][j].im = 0.;
c[i][j].re = ll.re + i * dx;
c[i][j].im = ll.im + j * dy;
pixel[i][j] = 1; // close to black
}
}
/*
* Iterate for number of iterations
*/
printf("Starting iterations ... \n");
int k=0;
unsigned int color;
for(k=0; k<number_of_iterations; k++){
/*
* Figure out the color for this iteration
*/
color = (unsigned int) ((k * 255 * 256 * 256 ) / number_of_iterations);
for (i=0; i<Nx; i++) {
int j=0;
for (j=0; j<Ny; j++) {
/*
* if pixel value is 0, no need to compute anything.
*/
Complex t = z[i][j];
/*
* check magnitude
*/
if (t.re * t.re + t.im*t.im < Max) {
/*
* Compute z_n+1 = z_n * z_n + c
*/
Complex znp1;
znp1.re = t.re * t.re - t.im * t.im + c[i][j].re;
znp1.im = 2.0 * t.re * t.im + c[i][j].im;
z[i][j] = znp1;
pixel[i][j] = color;
} else {
pixel[i][j] = 0; // black
}
//put draw part here
guchar red = pixel[i][j] & 0xff;
guchar green = pixel[i][j] & 0xff00;
guchar blue = pixel[i][j] & 0xff0000;
guchar alpha = 255; //opacity
put_pixel( pixbuf, i, j, red, green, blue, alpha);
}
}
}
printf("Done with iterations \n");
GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
GtkWidget* image = gtk_image_new();
gtk_image_set_from_pixbuf((GtkImage*) image, pixbuf);
/*
* The next 7 lines of code are NOW used to end the program if x button
*/
GdkScreen* screen = gtk_widget_get_screen (GTK_WIDGET (window));
GdkVisual* visual = gdk_screen_get_rgba_visual (screen);
if (visual == NULL)
visual = gdk_screen_get_system_visual (screen);
g_signal_connect(G_OBJECT (window), "destroy",
G_CALLBACK (destroy), NULL);
gtk_container_add(GTK_CONTAINER (window), image);
gtk_widget_show_all(window);
gtk_widget_queue_draw(image);
gtk_main();
return 0;
}//end of main
/*
* put_pixel - from: https://developer.gnome.org/gdk-pixbuf/stable/gdk-pixbuf-The-GdkPixbuf-Structure.html
*/
static void
put_pixel (GdkPixbuf *pixbuf,
int x, int y,
guchar red, guchar green,
guchar blue, guchar alpha) {
int n_channels = gdk_pixbuf_get_n_channels (pixbuf);
g_assert (gdk_pixbuf_get_colorspace (pixbuf) == GDK_COLORSPACE_RGB);
g_assert (gdk_pixbuf_get_bits_per_sample (pixbuf) == 8);
g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
g_assert (n_channels == 4);
int width = gdk_pixbuf_get_width (pixbuf);
int height = gdk_pixbuf_get_height (pixbuf);
g_assert (x >= 0 && x < width);
g_assert (y >= 0 && y < height);
int rowstride = gdk_pixbuf_get_rowstride (pixbuf);
guchar* pixels = gdk_pixbuf_get_pixels (pixbuf);
guchar* p = pixels + y * rowstride + x * n_channels;
p[0] = red;
p[1] = green;
p[2] = blue;
p[3] = alpha;
}
I am trying to have the color of the shape multi-colored. Currently it only outputs with 1 color.
I think it may be something to do with the iterations. And the color not changing from iteration to iteration.
Any help would be great.