/**********************************************************************/



/*       OUTLINE OF A PROGRAM FOR EDGE DETECTION ON GREY LEVEL IMAGES */



/*       EXAMPLE FOR  READING AND WRITING A PICTURE FILE              */



/*                                                                    */



/*     compiling:  cc edge2.c rasio.c -o edge2

-lm                            */

/*     running:    edge2 threshold inpic_file outpic_file           */

/*     Murali Subbarao, ESE 558 Digital Image Processing              */



/**********************************************************************/



#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include <string.h>

#include "rasio.h"



float  thresh;  /* global variable used for parameter passing */



void main(int argc, char *argv[])



{



 Raster_file *raster_file_in;               /* input file */

 Raster_header *raster_header_in;           /* header of input file */



 unsigned char **inpic, **outpic;

 int width, height;

 int i=0, j=0;

 char infilename[100], outfilename[100];

        void  process_image(unsigned char ** , unsigned char ** , int ,

int );





 if(argc != 4){

  fprintf(stderr, "Usage : edge2 threshold infilename outfilename\n");

  exit(1);

 }

 strcpy(infilename, argv[2]);

 strcpy(outfilename, argv[3]);

 thresh = (float)atof(argv[1]); /* read threshold */



 if(thresh>255.0) {

  fprintf(stderr,"threshold should be <= 255\n");

  exit(1);

 }

if(thresh<0.0) {

  fprintf(stderr,"threshold should be >= 0.0\n");

  exit(1);

 }




    /* read in input file */

    raster_file_in = read_raster_file( infilename);

    raster_header_in = raster_file_in->header;

    height = raster_header_in->height;

    width  = raster_header_in->width;





/* allocate 2-d image array  */

 inpic = raster_file_in->image;

 outpic = pic_alloc(height, width);



        process_image(inpic, outpic, height, width);





 /* change the value of height and width here if needed */





    /* write out image to a file */

    write_raster_file( outfilename, outpic, height, width);

    free_pic(inpic,height);
	free_pic(outpic,height);

} /* end main */







void process_image( unsigned char **inpic , unsigned char **outpic, int

height, int width)

{

   int i,j;

   float gradmag;

   extern float thresh;

/* Manipulate the contents of inpic[i][j] and compute outpic[i][j] */



/* Print the top left corner of input picture for

   examination on the terminal. This assumes that the
   image is larger than 16x16. 
   Comment out this part after initial testing. */

 for(i=0; ((i< 16) && (i<height));i++) {

  for(j=0; ((j< 16) && (j<width));j++)

   fprintf(stderr,"%5d",inpic[i][j]);

  fprintf(stderr,"\n");

 }



 /* compute outpic[i][j] */

 for(i=0;i<height-1;i++) {

  for(j=0;j<width-1;j++) {

   gradmag = (float) sqrt((double)

    ((inpic[i+1][j]-inpic[i][j])*

    (inpic[i+1][j]-inpic[i][j])+

    (inpic[i][j+1]-inpic[i][j])*

    (inpic[i][j+1]-inpic[i][j]))

    );

   if(gradmag>thresh) outpic[i][j]=200;

   else outpic[i][j]=5;

  }

 }



 for(i=0;i<height;i++) {  // deal with last column

  outpic[i][width-1] =5;

 }

 for(i=0;i<width;i++) {       // deal with last row.

  outpic[height-1][i] =5;

 }

}