i try to use bwlabel, but there error that i can't fix

>> BW=imread('b.jpg');
>> L=bwlabel(BW);
Error using bwlabel
Expected input number 1, BW, to be two-dimensional.

...

please help

Answer 1

[Walter Roberson]

jpg files are almost always RGB images even if they look like black and white. You need to rgb2gray() the content and perhaps im2bw() the result.

[ElizabethR]

thank you so much :D

Answer 2

[Image Analyst]

You call it BW but it's most likely not a binary image. It's probably gray scale or color. You need to binarize your grayscale image first. For example threshold it

grayImage = imread(filename);
BW = grayImage < 100;

[ElizabethR]

thank you so much .. but, how to calculate the wide of object in binary image ?

[Image Analyst]

See my Image Segmentation Tutorial. It will show you how. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862