Create a crop mask for map shapes

This function generates a mask polygon that can be overlaid on a map to crop it to various shapes (circle, ellipse, etc.). The mask is a polygon with a hole in the desired shape.

Usage

create_crop_mask(bbox, crop_shape, bg_color)

Arguments

bbox

Bounding box as a numeric vector c(xmin, ymin, xmax, ymax)

crop_shape

Shape to crop to. Options: "circle", "ellipse"

bg_color

Background color for the mask (should match plot background)

Value

A list with 'mask' (sf polygon object) and 'adjusted_bbox' (bbox, unchanged)

Examples

bbox <- c(-0.1, 51.5, 0.1, 51.6)
result <- create_crop_mask(bbox, "circle", "#0a0e27")