deal with images in the RGBA format

[yanyan-li]

the RGBA image in DTU

For example, in DTU, the RGBA image looks like this :

In camera_utils.py

we have to make it as a general RGB image.
if cam_info.image.mode == 'RGBA':
img = transparence2white(cam_info.image)
resized_image_rgb = PILtoTorch(img, resolution)