Changing --imSize seems to break eval.py functionality

[S4WRXTTCS]

With the default value of 256 for --imSize, the eval.py produces 768x256 images that comprises of the validation img image, the validation gt image, and the output from the uNet Model. The images look as expected. It's a really nice output as one can compare results.

But, when I change that value to 512 the image that it outputs is incorrect. It has the correct 1536x512 image size, but the validation img part is 256x512, and the validation gt part is also 256x512.