#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include "render.h"
#define IDX(n) ((n) % 3)

void applySeparableGaussianBlur(float[][MAT_SIZE], float[][MAT_SIZE], float[3], float[3]);
int main() {
	float inputImage[MAT_SIZE][MAT_SIZE];
	Render(inputImage);

	float kx[3] = {1.0f/4, 1.0f/2, 1.0f/4};
	float ky[3] = {1.0f/4, 1.0f/2, 1.0f/4};
	float outputImage[MAT_SIZE][MAT_SIZE] = {0};
	clock_t start = clock();
	applySeparableGaussianBlur(inputImage, outputImage, kx, ky);
	clock_t end   = clock();
	printf("Time: %lf s\n", (double)(end-start) / CLOCKS_PER_SEC);
	Print(outputImage);
}

void applySeparableGaussianBlur(float src[][MAT_SIZE], float dst[][MAT_SIZE], float kx[3], float ky[3]) {
	float buf[3][MAT_SIZE+3];
	int i, j;
	// 计算前两行的行内卷积
	for(i=0; i<2; i++)
	for(j=1; j<MAT_SIZE-1; j++) {
		buf[i][j] = src[i][j-1]*kx[0]+src[i][j]*kx[1]+src[i][j+1]*kx[2];
	}
	// 利用buf进行累计
	for(i=1; i<MAT_SIZE-1; i++) {
		for(j=1; j<MAT_SIZE-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(j=1; j<MAT_SIZE-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];
	}
}