Load customized dataset

[Jianhao-zheng]

Hi, I tried to run CF-GS on my customized dataset and I found there may be a potential bug in "trainer/trainer.py". It appears between line 276-280:

            if min(width, height) > 1000:
                width = width // 2
                height = height // 2
            
            intr_mat[:2, :] /= 2

I think "intr_mat[:2, :] /= 2" should also go under the if condition. I think the logic is if the images are too big, you resize the resolution by half and modify the intrinsic accordingly. But the current code divide the intrinsic by half even if the image has low resolution.