Saving a Bilevel - or Binary Image

Hello,

     I am creating a black and white movie in my code.  I create a 4 dimensional matrix of zeros.  Each number in the matrix is a uint8.  This is the problem.
B = zeros(X, Y, 1, NumberOfFrames);
B = uint8(B);  

All I want to save is a 1 and a 0.  By doing a unit8 I add 7 extra bits to each pixel.  This is over a 25 minute mov file!! How can I save the information using less memory?  Is there for example an: 

   B = binary(B); 
Command?

Thanks!

Answer 1

[Sean de Wolski]

 B = false(X, Y, 1, NumberOfFrames); %casts as logical (1bit)

or

 B = logical(B); %for something already in black and white but not 1bit

Answer 2

[Siddharth Shankar]

B = zeros(X, Y, 1, NumberOfFrames);
B = logical(B);

is what you are looking for. More info here: Logical Types

[Sean de Wolski]

This wastes all sorts of memory on the preallocation of B in class double (64bit) which is then immediately truncated to binary (1bit). Don't do this!

[Matthew Moynihan]

Yes, I know, I used the Repmat function to duplicate the logical value.

[Siddharth Shankar]

Sean, the code provided above is by no means meant to be "best practice" or the "best way" to do something. I was simply working off the code that "justthebasics" provided. The key was to make him aware of the LOGICAL function.