dilate.cpp

IplImage* dilate( const IplImage* src, const IplImage* kernel){

    //create a destination image with the same parametrs as the source image
    IplImage* dst = cvCreateImage(cvSize(src->height, src->width), IPL_DEPTH_8U, 1);
    
    vector<uchar> pix_values; //to store all the pixels that are covered
    int i, j;

    //loop over each row
    for( int row = 0; row < src->height; row++ ){

	//intialise pointers to the start of the row of destination image
	uchar* dst_row_ptr = (uchar*)(dst->imageData + row*dst->widthStep);

	//loop over each column in the row
	for( int column = 0; column < src->width; column++ ){

            /* for every pixel in the image at (row, column)
	     * collect the intensities of all the pixels
	     * swept over by the kernel, in the vector pix_values
	     */

	    pix_values.clear();

	    for( int krow = 0; krow < kernel->height; krow++){

		/* i marks the rows of the source image that are swept by the kernel
		 * so initialise a temp pointer to the ith row of the source
		 * and krow row of the kernel
		 */

		i = row + krow - kernel->height/2;
		uchar* src_row_ptr = (uchar*)(src->imageData + i*src->widthStep);
		uchar* kernel_row_ptr = (uchar*)(kernel->imageData + krow*kernel->widthStep);

		for( int kcolumn = 0; kcolumn < kernel->width; kcolumn++){

		    // j marks the columns of the source image that are swept by the kernel
		    j = column + kcolumn - kernel->width/2;


		    /* the value at the (i, j) pixel of the source is to be collected
		     * if (i, j) lie on the image and
		     * the kernel's pixel at the same location is foreground
		     */

		    if(i >= 0 && i < src->height && j >= 0 && j < src->width)
			if( kernel_row_ptr[kcolumn] == 255 )
			    pix_values.push_back(src_row_ptr[j]);
		}
	    }

	    /* max or min value of all the collected pixel goes in the desitnaiton
	     * for dilation or erosion respectively
	     */

	    dst_row_ptr[column] = *max_element(pix_values.begin(), pix_values.end()); //the max goes in the destination
	}
    }

    return dst;
}