add overlap images for saveImage

[jnwnlee]

As I thought generating full FLAME result is one of the strong points of DECA, I added some code to show the full FLAME image as a result. @YadiraF

<new jpg output files for --saveImage option in demo_reconstruct.py> original input overlap with shape image full shape image

[yfeng95]

Hi Junwon,

Thanks a lot for this, yes I agree that this function is quite useful.
However, I found your implementation only works for full shape images and it is a bit difficult to extend this for more rendering options. So I just implemented my version that you can render the results (shape, shap details, etc.) in original images size by setting --render_orig True.

Thanks, Yao

[jnwnlee]

There seems to be an issue regarding pytorch3d rasterizer (not the standard one) at the rendering part. Please check issue #78