Convert mask to polygon geometries

Extracts cell boundaries from a label mask and returns them as polygon geometries. If the sf package is available, returns an sf data frame; otherwise returns a tibble of boundary coordinates.

Usage

sg_mask_to_polygons(mask, simplify = TRUE, tolerance = 1)

Arguments

mask

An sg_mask object.

simplify

Logical. Simplify polygon geometries? Default TRUE.

tolerance

Numeric. Simplification tolerance in pixels when simplify = TRUE. Default 1.0.

Value

An sf data frame with one row per cell (columns cell_id and geometry) when sf is available, or a tibble with columns cell_id, row, col listing boundary coordinates.

Examples

labels <- matrix(0L, nrow = 20, ncol = 20)
labels[3:8, 3:8] <- 1L
labels[12:18, 12:18] <- 2L
mask <- new_sg_mask(labels)
polys <- sg_mask_to_polygons(mask, simplify = FALSE)
head(polys)
#> Simple feature collection with 2 features and 1 field
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 3 ymin: 3 xmax: 18 ymax: 18
#> CRS:           NA
#>   cell_id                       geometry
#> 1       1 POLYGON ((8 3, 3 3, 3 8, 8 ...
#> 2       2 POLYGON ((18 12, 12 12, 12 ...