Converting an image with specific values to black and white

I have an image that has only three values(i.e; 56, 98, 170). Those values represent different labels. How can I convert such image to only black and white without graylevels?

This may exapnad to having 4-vaues, 5-values, ...etc.

But, I think that if a solution was gained for three values, this could be applied to more than three value.

Thanks.

[Walter Roberson]

Which of the values should be converted to black, and which to white? Or do you want a three-level output?

Answer 1

[Walter Roberson]

bwimage = (YourImage == 170);

This assumes that 56 and 98 are both to convert to black. If the constants such as 170 are really floating point values such as .539 then you will need to modify slightly; see http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F