error when applying getSiameseBatch function

I tried to apply this example

https://www.mathworks.com/help/deeplearning/ug/train-a-siamese-network-to-compare-images.html

for signature verification

but there was an error when i tried to apply getSiameseBatch function

this was the error :Unable to perform assignment because the size of the left side is 813-by-962 and the size of the right

side is 796-by-1279.

can anyone help me to modify the function for running the example?

or can anyone illustrate the error for me?