The crop box's width and height times UserUnit and Scale, each rounded up to whole pixels (at least 1),
swapped when the total rotation is 90 or 270 degrees; with a Region, the size of the pixels the region covers.
Remarks
ISO 32000-2 §14.11.2 and §7.7.3.3 Table 31. Rounding up keeps every pixel the crop box touches (the spirit of §10.7.4, which
paints every pixel a shape intersects).