Code for simple edge detection using C

• remember to give file name with .bmp extension
• it will only work with 8 bit images

Code for simple edge  detection using C

#include<stdlib.h>
#include<stdio.h>
#include<math.h>
void main()
{
     FILE *imag1, *imag2;
    int i=0,byte,q;
   char namein[30];
    char nameout[30];
    printf("enter name of input image with extension \n");
    gets(namein);
    printf("enter name of output image with extension \n");
    gets(nameout);
  //..................clone image..................
   imag1=fopen(namein,"rb+");
   if(imag1==NULL)
    printf("cannot open file");
   imag2=fopen(nameout,"wb");
   while(!feof(imag1))
   {
       fputc(fgetc(imag1),imag2);
   }
//...............................end clone image...................
    int pic[400][600];
    FILE *fp;
    fp=fopen(nameout,"rb+");
    //for(i=0;i<54;i++) byte = getc(fp);
 fseek( fp,55,SEEK_SET );
   for(q=1;q<300;q++)
        for(i=1;i<600;i++)
        {
       //  printf("Pixel ->%d \n",getc(fp));
         pic[q][i]=getc(fp);
        }
fclose(fp);

//................pix alter.................

int temp1;
    FILE *fp2;
    fp2=fopen(nameout,"rb+");
 //   for(i=0;i<54;i++) byte = getc(fp);
 fseek( fp2,55,SEEK_SET );
 // printf("%d",q);
 //printf("pic array mid value %d \n",pic[60][500]);
   for(q=0;q<250;q++)
        for(i=2;i<400;i++)
        {
            temp1=(-1*pic[i-1][q])+(1*pic[i+1][q]);
            temp1=temp1*temp1;
            temp1=sqrt(temp1);
            printf("mod pixel sqrt res %d \n",temp1);
            printf("pic array value %d \n",temp1);
     //  putc(0,fp2);
       putc(temp1,fp2);
      //   printf("mod pix %d \n",getc(fp2));
    }


fclose(fp2);

}

************************* output**********************************

Here is a 8 bit image for you to try

A little for you to understand...........

Description  for Edge Detection

Take input from the user:

1)      We take  the name of the original file in which we want to implement Edge detection.

2)      Than we give the name of the new image we will show the detected edges

//……………………………………implementation…………………………………………………………………………

   char namein[30];

    char nameout[30];

printf("enter name of input image with extension \n");

    gets(namein);                               // name for input image (original image)

    printf("enter name of output image with extension \n");

    gets(nameout);            // name for output image (will be created at run time)

//……………………………………implementation…………………………………………………………………………

Than we clone our orignal image (create a copy of our image)

//..................clone image..................

   imag1=fopen(namein,"rb+");        //original image

   if(imag1==NULL)

    printf("cannot open file");

   imag2=fopen(nameout,"wb");  // clone image

   while(!feof(imag1))

   {

       fputc(fgetc(imag1),imag2);                   //copy image

   }

//...............................end clone image...................

Read the clone image and store the value of pixels in a 2D array named as pic[][]

    int pic[400][600];

    FILE *fp;

    fp=fopen(nameout,"rb+");

 fseek( fp,55,SEEK_SET );              //filtering out image header

   for(q=1;q<300;q++)

        for(i=1;i<600;i++)

        {

       //  printf("Pixel ->%d \n",getc(fp));  //to pint value of pixels

         pic[q][i]=getc(fp);                                   //storing pixel values in matrix

        }

fclose(fp);

Find gradient using the matrix pic[][] and store its value in a integer type variable named as  temp1 and write its value in the clone image

                Gradient will be calculated by convolving a 3 by 1 kernal in image [-1,0,1]

//..............................................pix alter...........................................................

int temp1;

    FILE *fp2;

    fp2=fopen(nameout,"rb+");

 //   for(i=0;i<54;i++) byte = getc(fp);

 fseek( fp2,55,SEEK_SET );                            // filtering out image header

 // printf("%d",q);

 //printf("pic array mid value %d \n",pic[60][500]);

   for(q=0;q<250;q++)     // implementing [-1,0,1] kernel to find out the integer value of gradient

        for(i=2;i<400;i++)

        {

            temp1=(-1*pic[i-1][q])+(1*pic[i+1][q]);      

            temp1=temp1*temp1;

            temp1=sqrt(temp1);

            printf("mod pixel sqrt res %d \n",temp1);

            printf("pic array value %d \n",temp1);

       putc(temp1,fp2);      // wrinting the value of gradient in clone image

      //   printf("mod pix %d \n",getc(fp2));

    }

fclose(fp2);

//..............................................pix alter...........................................................