Rescale an ROI between pyramid levels

Transform an ROI's coordinates from one pyramid level to another, assuming a power-of-two pyramid. For an exact transform against a real image pyramid (which need not be power-of-two), use at_transform() with the annot_image.

Usage

at_roi_rescale(
  roi,
  from_level = roi$level,
  to_level,
  call = rlang::caller_env()
)

Arguments

roi

An annot_roi.

from_level

Integer source pyramid level. Defaults to the ROI's own level; any other value is an error, because the coordinates are stored at that level.

to_level

Integer target pyramid level.

call

The calling environment, for error reporting.

Value

An annot_roi with coordinates at to_level and its level field set to to_level. Power-of-two scaling is exact in floating point, so the transform is exactly invertible.

See also

at_transform()

Other geometry: at_check_containment(), at_check_geometry(), at_clamp(), at_fix_geometry(), at_flip_y(), at_roi_buffer(), at_roi_contains(), at_roi_distance(), at_roi_overlaps(), at_roi_ring(), at_roi_setops, at_roi_simplify(), at_rois_overlap(), at_snap(), at_transform()

Examples

r <- at_roi_rect(0, 0, 100, 100, label = "a")
r2 <- at_roi_rescale(r, from_level = 0, to_level = 2)
identical(
  sf::st_coordinates(sf::st_geometry(r)),
  sf::st_coordinates(sf::st_geometry(at_roi_rescale(r2, 2, 0)))
)
#> [1] TRUE