Grey Scaling.

Making all the three pixels take up the value of their average values gives a gray scale effect. This however is very rudimentary, method of grey scaling. The image looks very ugly so I'm not putting it up. ;-)!

	average=(pixel.red+pixel.green+pixel.blue)/3;
        pixel.red   =average;			
        pixel.green =average;		
        pixel.blue  =average;

#include<gtk/gtk.h>

void colorgrey_picture(GdkPixbuf *pb)
{ 
  int ht,wt;
  int i=0,j=0;
  int rowstride=0;  
  int bpp=0;
  double avg=0;
  gchar *pixel;


  if(gdk_pixbuf_get_bits_per_sample(pb)!=8)   //we handle only 24 bit images.
  	return;                               //look at 3 bytes per pixel.

  bpp=3;	         	  //getting attributes of height,
  ht=gdk_pixbuf_get_height(pb);   //width, and bpp.Also get pointer
  wt=gdk_pixbuf_get_width(pb);	  //to pixels.
  pixel=gdk_pixbuf_get_pixels(pb);
  rowstride=wt*bpp;

  for(i=0;i<ht;i++)		//iterate over the height of image.
    for(j=0;j<rowstride;j+=bpp)   //read every pixel in the row.skip
				//bpp bytes 
      {	
      
	//find avg of the pixel to grey it.

	avg+=pixel[i*rowstride + j+0]+pixel[i*rowstride + j+1]+pixel[i*rowstride + j+2];
	avg/=3.00;
	avg=((int)(avg))%256;

	pixel[i*rowstride + j+0]=(int)avg;
	pixel[i*rowstride + j+1]=(int)avg;
	pixel[i*rowstride + j+2]=(int)avg;
      }  
  return;
}

% <!-- provide link here-->
% complete working example with glue code in example_colorgrey.c