median filter

median3x3.cc

template<typename type>
inline void swap_sort(type& a, type& b) {
	if (a > b) {
		type temp = a;
		a = b;
		b = temp;
	}
}
#include<array>
// source: http://ndevilla.free.fr/median/median.pdf
template<typename dtype>
inline dtype median9(std::array<dtype, 9> arr) {
	swap_sort(arr[1], arr[2]);
	swap_sort(arr[4], arr[5]);
	swap_sort(arr[7], arr[8]);
	swap_sort(arr[0], arr[1]);
	swap_sort(arr[3], arr[4]);
	swap_sort(arr[6], arr[7]);
	swap_sort(arr[1], arr[2]);
	swap_sort(arr[4], arr[5]);
	swap_sort(arr[7], arr[8]);
	swap_sort(arr[0], arr[3]);
	swap_sort(arr[5], arr[8]);
	swap_sort(arr[4], arr[7]);
	swap_sort(arr[3], arr[6]);
	swap_sort(arr[1], arr[4]);
	swap_sort(arr[2], arr[5]);
	swap_sort(arr[4], arr[7]);
	swap_sort(arr[4], arr[2]);
	swap_sort(arr[6], arr[4]);
	swap_sort(arr[4], arr[2]);
	return arr[4];
}
template<typename dtype, typename itype>
void median_filter(dtype* dst, const dtype* src, itype height, itype width) {
	for (itype h=0; h<height; h++)
	for (itype w=0; w<width; w++) {
		if (h == 0 or h == height-1 or w == 0 or w == width-1)
			dst[h*width+w] = src[h*width+w];
		else {
			std::array<dtype, 9> arr = {
				src[h*width+w],
				src[h*width+w+1],
				src[h*width+w-1],
				src[(h+1)*width+w],
				src[(h-1)*width+w],
				src[(h+1)*width+w+1],
				src[(h+1)*width+w-1],
				src[(h-1)*width+w+1],
				src[(h-1)*width+w-1],
			};
			dst[h*width+w] = median9<dtype>(arr);
		}
	}
}
#include<cstdio>
#include<ctime>
#include<cstdint>
#include<cstdlib>
const int width = 800;
const int height = 600;
int main() {
    std::srand(123141);
    double* src = (double*)std::malloc(height * width * sizeof(double));
    double* dst = (double*)std::malloc(height * width * sizeof(double));
    for (int i = 0; i < (height * width); i++) {
        src[i] = ((double)(std::rand() % 1000)) / 1000;
    }
    auto t1 = std::clock();
    // for (int i=0; i<100; i++)
        median_filter(dst, src, height, width);
    auto t2 = std::clock();
    std::printf("time: %f\n", double(t2-t1) / CLOCKS_PER_SEC);
}