pixel plotting template

gistfile1.c

#include <gtk/gtk.h>
#include <stdlib.h>
#include <stdio.h>

void put_pixel(GdkPixbuf *pixbuf, int x, int y, guchar red, guchar green, guchar blue, guchar alpha);

struct widgets
{
  GtkWidget *window, *image;
  GdkPixbuf *pixbuf;
};

int main (int argc, char *argv[])
{
  struct widgets w;

  gtk_init(&argc, &argv);

  w.window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  
  w.pixbuf = gdk_pixbuf_new(GDK_COLORSPACE_RGB, 0, 8, 640, 480);

  w.image = gtk_image_new_from_pixbuf(w.pixbuf);
  
  gtk_container_add(GTK_CONTAINER(w.window), GTK_WIDGET(w.image));

  gtk_widget_show_all(w.window);

  g_signal_connect_swapped(G_OBJECT(w.window), "destroy", G_CALLBACK(gtk_main_quit), NULL);

  /*Put pixel array (w.pixbuf) manipulation code here*/

  /*EXAMPLE*/
  int x,y;

  for (x = 0; x < 640; x++)
    {
      for (y = 0; y < 480; y++)
	{
	  put_pixel(w.pixbuf, (int)x, (int)y, (guchar)x, (guchar)y, (guchar)x+y, 255);
	}
    }
  /*END OF EXAMPLE*/

  gtk_image_set_from_pixbuf((GtkImage *)w.image, w.pixbuf);

  gtk_main();

  return 0;
}

void put_pixel(GdkPixbuf *pixbuf, int x, int y, guchar red, guchar green, guchar blue, guchar alpha)
{
  guchar *pixels, *p;
  int rowstride, numchannels;
  
  numchannels = gdk_pixbuf_get_n_channels(pixbuf);
  rowstride = gdk_pixbuf_get_rowstride(pixbuf);
  pixels = gdk_pixbuf_get_pixels(pixbuf);

  p = pixels + y * rowstride + x * numchannels;

  p[0] = red;
  p[1] = green;
  p[2] = blue;
  p[3] = alpha;
}