How do I change the color channel's value using variables?

I am working on a project which aims to recolor a certain part of an image. I created a matlab function that accepts numerical values for the RGB channels. However, this code will only run once smoothly, then on the succeeding executions, a mismatch error will appear. What seems to be the problem with my code? Thanks :)

        % Extract the individual red, green, and blue color channels.
        redChannel = maskedImage(:, :, 1);
        greenChannel = maskedImage(:, :, 2);
        blueChannel = maskedImage(:, :, 3);
        % Make the red channel that color

        redChannel(edge2) = red;
        greenChannel(edge2) = grn;
        blueChannel(edge2) = blu;        
        maskedImage = cat(3, redChannel, greenChannel, blueChannel);

[Adam]

You haven't given us the definitions of red, grn, blu, edge2 or the full code showing how exactly you perform 'succeeding executions' nor what the exact error message is and to which line it refers. Without this information it is hard to say much.

[Image Analyst]

Are you sure red, grn, and blu are uint8 values in the range 0-255, not floating point in the range 0-1? And are you sure edge2 is a 2-D binary image of type logical?

[Maria Jeseca Baculo]

edge2 is the part of the image I wanted to change the color (sorry for the inappropriate naming) and red grn and blu were the parameters accepted by the matlab function. i.e.:

function newImage = ChangeColor(red, grn,blu)

the error appears in the lines:

        redChannel(edge2) = red;
        greenChannel(edge2) = grn;
        blueChannel(edge2) = blu;

which says: In an assignment A(:) = B, the number of elements in A and B must be the same. I'm sorry if the question is vague. Thanks in advance!

[Maria Jeseca Baculo]

also, the parameters are sent by a python web app via matlab engine. Thanks again :)

[Maria Jeseca Baculo]

yes, I made sure that the values are uint8 values, the thing is, the code works fine with constant values. But when these variables are used, it only runs once without the error.

Answer 1

[Image Analyst]

Either edge2 is not the same size as redChannel, or red is not a single number but an array.

[Maria Jeseca Baculo]

I tried converting the arguments to int in python prior passing them in matlab and now it works! Thank you :)