blur.c

#include "bmp.h"

#define kern_size 9
#define max_weight 9993

int gaussian_filter[9][9] = {                                                    
  { 8,  18,  34,  50,  56,  50,  34,  18,  8},                                   
  {18,  44,  82, 119, 135, 119,  82,  44, 18},                                   
  {34,  82, 153, 223, 253, 223, 153,  82, 34},                                   
  {50, 119, 223, 325, 368, 325, 223, 119, 50},                                   
  {56, 135, 253, 368, 417, 368, 253, 135, 56},                                   
  {50, 119, 223, 325, 368, 325, 223, 119, 50},                                   
  {34,  82, 153, 223, 253, 223, 153,  82, 34},                                   
  {18,  44,  82, 119, 135, 119,  82,  44, 18},                                   
  { 8,  18,  34,  50,  56,  50,  34,  18,  8}                                    
};

void blur(BMP *bmp, BMP *blurbmp)
{
	int i, j, k, l, weight;
	int acc[3], idx[3];
	int kern_len = kern_size/2;
	Pixel *pixel;

	for(i = 0; i < bmp->height; i++){
		for(j = 0; j < bmp->width; j++){
			acc[0] = 0; acc[1] = 0; acc[2] = 0;
			weight = max_weight;
      for(k = 0; k < kern_size; k++){                                          
        for(l = 0; l < kern_size; l++){                                        
          idx[1] = j - kern_len + l;                                             
          idx[2] = i - kern_len + k;                                             
					idx[0] = idx[2]*bmp->width + idx[1];
          if((idx[1] >= 0) && (idx[2] >=0) && 
						(idx[1] < bmp->width) && (idx[2] < bmp->height)){
            pixel = (Pixel *) &bmp->data[idx[0]*sizeof(Pixel)];
						acc[0] += gaussian_filter[k][l] * (pixel->R - 0);
						acc[1] += gaussian_filter[k][l] * (pixel->G - 0);
						acc[2] += gaussian_filter[k][l] * (pixel->B - 0);
					}
					else
						weight -= gaussian_filter[k][l];
        }                                                                        
      }		
			pixel = (Pixel *) &blurbmp->data[(i*blurbmp->width + j)*sizeof(Pixel)];
			pixel->R = acc[0]/weight;
			pixel->G = acc[1]/weight;
			pixel->B = acc[2]/weight;
		}
	}
}

int main(int argc, char *argv[]) {
		char input[] = "input.bmp";
		char output[] = "blur.bmp";

		BMP bmp, blurbmp;

    bmpLoad(&bmp, input);
		blurbmp = bmp;
		blur(&bmp, &blurbmp);
    bmpSave(&blurbmp, output);

    return 0;
}