MATLAB: Help Stitching Photos Together

Computer Vision Toolboximage processingpanoramastitching

I am trying to stitch 2 photos together using the reference code found here almost verbatim http://www.mathworks.com/help/vision/examples/feature-based-panoramic-image-stitching.html
Some differences:
My photos are already greyscale, so I skip line:
grayImage = rgb2gray(I);
and just have:
grayImage = I;
I have only 2 photos of identical size (in pixels), so I am retaining the transformation of the second image relative to the first image, i.e. totally skipping the code in the example that "invert[s] the transform for the center image and apply[s] that transform to all the others." This means that tforms(1) remains an identity matrix as created by the initializing statement:
     tforms(buildingScene.Count) = projective2d(eye(3));
I don't get any errors until almost the last line:
Error using AlphaBlender/step
The Image 1 and Image 2 inputs must have the same number of dimensions.
Error in stitchCntl (line xxx)
panorama = step(blender, panorama, warpedImage, warpedImage(:,:,1));
I have goggled the error message with no hits, and am at a loss as to how to proceed. Any help is greatly appreciated.
Thank you to all!

Best Answer

OK, I have something...
I changed....
% Initialize the "empty" panorama.
panorama = zeros([height width 3], 'like', I)
To...
panorama = zeros([height width], 'like', I)
I now get two stitched-together photos. I think this was because I have grayscale photos, not color photos as in the example.
Unfortunatley, matchFeatures() did a horrible job finding common features and so the splice is terrible, but I guess that is a different story entirely.
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