Question

Matlab图像处理中运用区域二值，输出图像全黑的问题..

[a,b] = size(input);
for i = 1:a/32
for j = 1:b/32
operatingRegion = input (32*(i-1)+1:32*i,32*(j-1)+1:32*j);
thresh = graythresh(operatingRegion);
operatingRegion = im2bw (operatingRegion, thresh);
input (32*(i-1)+1:32*i,32*(j-1)+1:32*j) = operatingRegion;
end
end
imshow(input);

刚刚接触matlab，想做个提取图片中特定信息的程序。input为一张灰度图，想法基本上是把图像分成若干32×32的区块，各自使用Ostu阈值分割确定阈值，二值化之后把该区块填回原图。然而结果是一片黑...简单测试以后发现貌似是这里开始出问题input (32*(i-1)+1:32*i,32*(j-1)+1:32*j) = operatingRegion;。请问是什么原因？怎么解决这个问题呢？

Answer 1

原因是：operatingRegion = im2bw (operatingRegion, thresh);得的数据是0和1，所以，input (32*(i-1)+1:32*i,32*(j-1)+1:32*j)也是0和1，而imshow(input)显示的范围是[0,255],1/255近似于0，所以，全显示为黑色。我给你改下：

[a,b] = size(input);
for i = 1:a/32
for j = 1:b/32
operatingRegion = input (32*(i-1)+1:32*i,32*(j-1)+1:32*j);
thresh = graythresh(operatingRegion);
operatingRegion = im2bw (operatingRegion, thresh);
input (32*(i-1)+1:32*i,32*(j-1)+1:32*j) = operatingRegion*255;
end
end
imshow(input);
按上面语句试试