Downsampling in calibrator.py makes detection fail

[martimorta-at-work]

Hi,
I was having issues detecting a checkerboard until I changed the downsampling size (below) from VGA for the actual size of the camera output.

image_pipeline/camera_calibration/src/camera_calibration/calibrator.py

Line 523 in 458ff61

scale = math.sqrt( (width*height) / (640.*480.) )

I think having that as a parameter would allow better calibrations unless I am missing something here.
I am happy to submit a PR with VGA size being a parameter if there aren't other implications.

Cheers!

[JWhitleyWork]

@martimorta-at-work I know it's going on almost a year since you submitted this but we would be happy to accept a PR with this.

[onurtore]

@JWhitleyWork,
Still interested? I can create a PR