Remove small patches from a binary raster

Identifies connected patches of 1-valued cells and removes (sets to 0) any patch whose area is below a size threshold.

Usage

fl_patch_rm(x, min_area, directions = 4L)

Arguments

x

A SpatRaster with binary values (0/1).

min_area

Numeric. Minimum patch area in map units squared (e.g., m²). Patches smaller than this are removed.

directions

Integer. 4 for rook connectivity, 8 for queen. Default 4 (matches VCA 4-connectivity convention).

Value

A SpatRaster with the same grid as x. Small patches are set to 0; all other values are unchanged.

Examples

slope <- terra::rast(system.file("testdata/slope.tif", package = "flooded"))
gentle <- fl_mask(slope, threshold = 9, operator = "<=")

# Remove patches smaller than 5000 m²
cleaned <- fl_patch_rm(gentle, min_area = 5000)
terra::plot(cleaned, col = c("grey90", "darkgreen"), main = "Large gentle-slope patches")