【二值化】sauvola算法实现

实现了sauvola算法，原论文去google一下就有了~

参数是：k, windowSize，自己调调看效果

void sauvola(unsigned char * grayImage,unsigned char * biImage,int w,int h,int k,int windowSize)
{	
	int whalf = windowSize >> 1;
	
	int i,j;
	int IMAGE_WIDTH = w;
	int IMAGE_HEIGHT = h;
	// create the integral image
	unsigned long * integralImg = (unsigned long*)malloc(IMAGE_WIDTH*IMAGE_HEIGHT*sizeof(unsigned long*));
	unsigned long * integralImgSqrt = (unsigned long*)malloc(IMAGE_WIDTH*IMAGE_HEIGHT*sizeof(unsigned long*));
	int sum = 0;
	int sqrtsum = 0;
	int index;
	for (i=0; i 0 && ymin == 0){
				diff = integralImg[ymax * IMAGE_WIDTH + xmax] - integralImg[ymax * IMAGE_WIDTH + xmin - 1];
				sqdiff = integralImgSqrt[ymax * IMAGE_WIDTH + xmax] - integralImgSqrt[ymax * IMAGE_WIDTH + xmin - 1];	
			}else if(xmin == 0 && ymin > 0){
				diff = integralImg[ymax * IMAGE_WIDTH + xmax] - integralImg[(ymin - 1) * IMAGE_WIDTH + xmax];
				sqdiff = integralImgSqrt[ymax * IMAGE_WIDTH + xmax] - integralImgSqrt[(ymin - 1) * IMAGE_WIDTH + xmax];;
			}else{
				diagsum = integralImg[ymax * IMAGE_WIDTH + xmax] + integralImg[(ymin - 1) * IMAGE_WIDTH + xmin - 1];
				idiagsum = integralImg[(ymin - 1) * IMAGE_WIDTH + xmax] + integralImg[ymax * IMAGE_WIDTH + xmin - 1];
				diff = diagsum - idiagsum;

				sqdiagsum = integralImgSqrt[ymax * IMAGE_WIDTH + xmax] + integralImgSqrt[(ymin - 1) * IMAGE_WIDTH + xmin - 1];
				sqidiagsum = integralImgSqrt[(ymin - 1) * IMAGE_WIDTH + xmax] + integralImgSqrt[ymax * IMAGE_WIDTH + xmin - 1];
				sqdiff = sqdiagsum - sqidiagsum;
			}

			mean = diff/area;
			std  = sqrt((sqdiff - diff*diff/area)/(area-1));
			threshold = mean*(1+k*((std/128)-1));
			if(grayImage[j*IMAGE_WIDTH + i] < threshold)
				biImage[j*IMAGE_WIDTH + i] = 0;
			else
				biImage[j*IMAGE_WIDTH + i] = 255;	
		}
	}
	
	free(integralImg);
	free(integralImgSqrt);
}