Possible to crop the video dynamicly？

[NickWang16]

in this part, it said that I should crop the orignal imageDefining cropping coordinates,how ever if I crop and save the fixed cropping coordinates, some time it will go out of the range, if it is possible to crop it dynamicly? So for example I can crop the img outside of DLC? or maybe how to crop it in DLC-napri, I did not see how to select the crop region and save it, Thank you so much!