title: weird binary image values generated by cvThreshold
body: <p>Hey, guys, i am using opencv to do some vehicle recognition work, and when i use cvThershold to convert the gray image to binary image, the return image is really strange, the binary image supposes to have only two values,0 and 255, however, it contains other values like 2,3,254,253, anyone knows how this happens, and also cvCmps also has this problem.</p>