convert this code to efficient way.

I have code that convert from org.bytedeco.javacv.Frame to matlab image.

In inefficient way. Can you help me convert it to efficient way?

    javaaddpath('javacv.jar')
    import org.bytedeco.javacv.*;
    import org.bytedeco.javacpp.*;
    grabber = FrameGrabber.createDefault(0)
    grabber.start()
    img = grabber.grab()
    buff = img.image(1);
    % //from here is inefficient code
    charBuff = buff.asCharBuffer;
    n = charBuff.length;
    data = repmat(uint16(0),n,1);
    for i=0:n-1
        data(i+1) = charBuff.get(i);
    end
    I = typecast(data, 'uint8');
    I = cat(3,                              ...
            reshape(I(3:3:end),[w h])', ...
            reshape(I(2:3:end),[w h])', ...
            reshape(I(1:3:end),[w h])'  ...
       );
    imshow(I);

[dpb]

Don't know what the form of buff is but why wouldn't

I=typecast(buff.asCharBuffer,'uint8');

be the same as what your end result is? Although I'd think there's likely a direct transformation if one knew the input format and what one's trying to get to in description rather than code...but I'm not an image processing guy at all, either, so what do I know??? :)