closes #2415

NAMESPACE

@@ -314,6 +314,7 @@ S3method(st_snap,sfg)
 S3method(st_sym_difference,sf)
 S3method(st_sym_difference,sfc)
 S3method(st_sym_difference,sfg)
+S3method(st_transform,bbox)
 S3method(st_transform,sf)
 S3method(st_transform,sfc)
 S3method(st_transform,sfg)

NEWS.md

@@ -1,5 +1,7 @@
 # version 1.0-17
 
+* add `st_transform()` method for `bbox` objects; this uses OGRCoordinateTransformation::TransformBounds(), densifying first and antemeridian proof; #2415
+
 * `st_filter.sf()` correctly scopes `x` and `y` arguments using !! operator; #2416
 
 * `[.sfc` and `[<-.sfc` use matrix/array type subsetting for `sfc` objects that have a `dim` attribute

R/transform.R

@@ -165,6 +165,14 @@ st_transform.sfg = function(x, crs = st_crs(x), ...) {
 	structure(st_transform(x, crs, ...)[[1]], crs = crs)
 }
 
+#' @name st_transform
+#' @export
+#' @param densify integer, number of points for discretizing lines between bounding box corner points; see Details
+#' @details the method for `bbox` objects densifies lines for geographic coordinates along Cartesian lines, not great circle arcs
+st_transform.bbox = function(x, crs, ..., densify = 21) {
+	st_bbox(CPL_transform_bounds(x, st_crs(crs), densify), crs = crs)
+}
+
 #' @name st_transform
 #' @export
 st_wrap_dateline = function(x, options, quiet) UseMethod("st_wrap_dateline")

src/gdal.cpp

@@ -698,6 +698,12 @@ Rcpp::NumericVector CPL_transform_bounds(Rcpp::NumericVector bb, Rcpp::List crs_
 	ret[1] = ymin;
 	ret[2] = xmax;
 	ret[3] = ymax;
+	Rcpp::CharacterVector names(4);
+	names(0) = "xmin";
+	names(1) = "ymin";
+	names(2) = "xmax";
+	names(3) = "ymax";
+	ret.attr("names") = names;
 	ct->DestroyCT(ct);
 	dst->Release();
 	src->Release();