Niblack---二值化算法

申明，本文非笔者原创，原文转载自：http://blog.csdn.net/cxf7394373/article/details/5787908

Niblack二值化算法是比较简单的局部阈值方法，阈值的计算公式是T = m + k*v，其中m为以该像素点为中心的区域的平均灰度值，v是该区域的标准差，k是一个系数，matlab程序如下：

 I = imread('card3.bmp');
 I = rgb2gray(I);

 w =  2;%
 max = 0;
 min = 0;
 [m,n] = size(I);
 T = zeros(m ,n );

 %
 for i = (w + 1):(m - w)
     for j = (w + 1):(n - w)
         sum = 0;
         for k = -w:w
             for l = -w:w
                 sum = sum + uint32(I(i + k,j + l));
             end
         end
         average = double(sum) /((2*w+1)*(2*w+1));
         s = 0;
         for k = -w:w
             for l = -w:w
                 s = s +   (uint32(I(i + k,j + l)) - average)*(uint32(I(i + k,j + l)) - average);
             end
         end
         s= sqrt(double(s)/((2*w+1)*(2*w+1)));

         T(i,j) = average + 0.2*s;
     end
 end
 for i =  1:m
     for j = 1:n
         if I(i,j) > T(i,j)
             I(i,j) = uint8(255);
         else
             I(i,j) = uint8(0);
         end
     end
 end
 imshow(I);

上述程序中选择的窗口大小是5*5，处理结果不好，产生了大量的噪声...