Camera backside problem solved and visualizing resolution control added

[Lee-Jun-Hyuk-37]

Dear maintainer,

Thank you so much for creating a very useful project.
I have solved one problem and added one feature.

1. While utilizing your project, I found one problem: when the vertex of the soccer field goes to backside of the camera, the line is drawn on the opposite side of the field from where it was intended. It is fine when both end vertices of the line go to the backside, but the problem occurs when only one of them goes to the backside. I have implemented all the exception handling for this.

When the vertex of the field went to the backside of the camera, it would look like this.

However, after I fixed the problem, it looks like below, just like we expected.

2. I also added one more feature. Previously, when visualizing the results, we could only display the output images in 256*455 resolution that the model receives as input, but I have added an option to change the resolution of the displayed image. The "ratio_width" and "ratio_height" parameters from draw_reprojection function are the options, and if you use the default settings, you'll get the same results as before.

Followings are the examples for the options.

Let's say shape of the raw input image is (1080, 1920), and we resample the image as shape (256, 455) for input to the model.
raw_shape = (1080, 1920)
resampled_shape = (256, 455)

we can use the options as below

fig, ax = viz.init_figure(raw_shape[1], raw_shape[0])
ax = viz.draw_image(ax, raw_image)
ax = viz.draw_reprojection(ax, object3dcpu, cam, ratio_width=raw_shape[1]/resampled_shape[1], 
                           ratio_height=raw_shape[1]/resampled_shape[1])

I appreciate your work, and I hope my pull request helps for you.

Sincerely,
Lee Jun Hyuk

[jtheiner]

Dear Lee Jun,

thanks for your contributions, in particular the visualization bug.
Before accepting the merge request, please revert the changes in the README.md.

[Lee-Jun-Hyuk-37]

I've reverted the changes in the README.md and opened a new pull request. Please review the new pull request.