Edge Enhancement

InitGraph();
rows=31;cols=47;
ScaleWindow(0, 0,cols+1, rows+1);
Colour(Black);
BoxFill(0,0,cols+1,rows+1);

pic1=new Array(cols);pic2=new Array(cols);
for(var i = 0;i<=cols;i++){
   pic1[i]=new Array(rows);pic2[i]=new Array(rows);
}
 
filt=new Array(3);
filt[0]=new Array( 1,-2, 1);   //A difference filter
filt[1]=new Array(-2, 4,-2);
filt[2]=new Array( 1,-2, 1);

//Set up picture with a diamond on shaded ground
Colour(Dull);
m=(rows+cols)/2;
for (i = 0;i<= cols;i++){ 
   for (j = 0; j<=rows;j++) {
      k = Math.abs(i - cols/2) + Math.abs(j - rows/2);
      if (k<rows/3) {k = 30;}else{k=0;};
      k = 100 + k + 2 * i;
      pic1 [i][j] = k;
      pic2 [i][j] = k; 
      c =  k;
      ColourRGB(c, c, c);
      BoxFill(i, j, 1, 1);
   }
}

filter();