box formats (XYXY, XYWH, CXCYWH)

Also written: XYXY, XYWH, CXCYWH

Three ways to write a box: XYXY is (x1, y1, x2, y2) for the top-left and bottom-right corners (torchvision's standard), XYWH is (x, y, width, height), and CXCYWH is the center plus width and height. Mixing them up draws boxes in the wrong place.