Matlab video manipulation

attempt1

clc;
clear;

% Start with importing the video

vidObj = VideoReader('/Users/DarkSector/Desktop/vid.avi');

% Once loaded lets get the first frame and choose an ROI on it
frame1 = read(vidObj, 1);

%now let's show the image and select the ROI on it

imshow(frame1)
roiRect = imrect;
roiPosition = roiRect.getPosition();
roiMask = createMask(roiRect);
%masked = createMask(roiRect, frame1);

mask_3chan = repmat(roiMask, [1,1,3]);
frame1(~mask_3chan) = 0;

% if we are not using the rest of the pixels, might as well remove
% them and crop the image.
% No reason to store dummy data
frame1 = imcrop(frame1, roiPosition);
%imshow(frame1)

red_channel = frame1;
red_channel(:,:,2) = 0;
red_channel(:,:,3) = 0;