How to remove the Alpha channel?

I have created an image via PowerPoint using only black and white colors and saved it as a ".tif" file. I want to convert it to an actual binary image in MATLAB but have a problem (the histogram of the intensity is not only 0 and 255 and has some pixels with intensity close to either 0 or 255).

When I open this image in MATLAB (using imread), the image size is m*m*4. I have previously opened such files (not created via PowerPoint though) but the size was m*m*3. How can I convert the m*m*4 image to a m*m*3 one? I think the added number is due to "alpha channel" but do not know how to remove it.

tnx in advance

Answer 1

[Image Analyst]

binaryImage = m(:,:,2) < 128;

[ramin bba]

So efficient! Would you mind elaborating a bit on the method (why did you choose 2)?

tnx