#include <stdio.h>
#include <time.h>

#define IDX(n)((n)%3)

float inputImage[5][5] = {
	{1,2,3,4,5},
	{6,7,8,9,10},
	{11,12,13,14,15},
	{16,17,18,19,20},
	{21,22,23,24,25}
};

float kx[3] = { 1.0f / 4,2.0f / 4,1.0f / 4 };
float ky[3] = { 1.0f / 4,2.0f / 4,1.0f / 4 };
float buf[3][3] = { 0 };

void applySeparableGaussianBlur(float src[][5], float dst[][5], int h, int w, float kx[], float ky[3]) {
	for (int i = 0; i < 2; ++i) {
		for (int j = 1; j < w - 1; ++j) {
			buf[i][j] = src[i][j - 1] * kx[0] + src[i][j] * kx[1] + src[i][j + 1] * kx[2];
		}
	}

	for (int i = 1; i < h - 1; ++i) {
		for (int j = 1; j < w - 1; ++j) {
			buf[IDX(i + 1)][j] = src[i + 1][j - 1] * kx[0] + src[i + 1][j] * kx[1] + src[i + 1][j + 1] * kx[2];
		}

		for (int j = 1; j < w - 1; ++j) {
			dst[i][j] = buf[IDX(i - 1)][j] * ky[0] + buf[IDX(i)][j] * ky[1] + buf[IDX(i + 1)][j] * ky[2];
		}
	}
}

int main() {
	float outputImage[5][5] = { 0 };
	clock_t start, end;
	start = clock();
	applySeparableGaussianBlur(inputImage, outputImage, 5, 5, kx, ky);
	end = clock();
	double timeSpent = (double)(end - start) / CLOCKS_PER_SEC;
	for (int i = 0; i < 5; i++) {
		for (int j = 0; j < 5; j++) {
			printf("%-4.1f ", outputImage[i][j]);
		}
		printf("\n");
	}
	printf("The timeSpent is %1.32f second\n", timeSpent);
}