function created for transform grayscale to binary doesn't work

Hi,

I've created this function m file to convert grayscale images to binary images (as gray2bin matlab function):

function conv_to_BW(im)

[m,n]=size(im);

BW=zeros(m,n);

for i=1:m
    for j=1:n
        if im(i,j)<10
            BW(i,j)=0;
        else BW(i,j)=1;
        end
    end
end

But, when I apply this function to a file in grayscale as:

conv_to_BW(grayscalefile);

it doesn't generate BW variable-image-matrix and doesn't generate m,n variables.

Answer 1

[Matt Fig]

You didn't specify a return value for your function. If you want your function to return something, you have to tell it to do so.

function BW = conv_to_BW(im)

[cyberdyne]

Ok...I've forgotten it. Thanks

[cyberdyne]

...and to put returned ans-variable in a variable BW ? (it currently displays BW as "ans")

[Matt Fig]

You should read the help for FUNCTION.

help function

[Sean de Wolski]

Welcome back Matt!

[Matt Fig]

Thanks, Sean de. (MathWorker!)

Answer 2

[John Petersen]

If you're interested, this should be faster code if your image is very large or you're doing many of them.

function BW = conv_to_BW(im)

[m,n]=size(im);
BW = ones(m,n);
BW(im<10)) = 0;