makeBoundaryDistance

Generate distance-to-class-boundary grids from mask chips

Usage

makeBoundaryDistance(chipsDir, noDataValue = 0)

Arguments

chipsDir

Full or relative path to the chips directory that contains a "masks" subfolder. This is the same directory that was used as the outDir argument to makeChips. Do not include a trailing slash.

noDataValue

Numeric scalar. The value written to every pixel of a distance grid when the corresponding mask chip contains no class boundaries (i.e. the chip belongs to a single class throughout). Default is 0.

Value

Distance-to-boundary raster files written to disk in TIFF format inside a "dist" subfolder (flat layout) or "dist/positive/" and "dist/background/" subfolders (divided layout). No R object is returned.

Details

This function reads raster mask chips from the "masks" subfolder of a chips directory created by makeChips and generates a corresponding distance surface for each mask. Each output raster encodes, for every pixel, the distance to the nearest class boundary. A class boundary is any pixel that is adjacent (in an 8-connected neighborhood) to at least one pixel belonging to a different class. Boundary pixels themselves receive a value of 0; all other pixels receive the Euclidean distance (in pixel units, unless the raster has a projected coordinate system, in which case map units are used) to the nearest boundary pixel. Output grids are written to a "dist" subfolder created inside the provided chips directory. Output files are named identically to their corresponding masks and are saved in TIFF format.

The function automatically detects whether the chips directory uses a flat layout (masks/) produced by makeChips with mode = "All" or mode = "Positive", or a divided layout (masks/positive/ and masks/background/) produced with mode = "Divided". For the divided layout, distance grids are written to dist/positive/ and dist/background/ respectively.

Examples

if (FALSE) { # \dontrun{
makeBoundaryDistance(chipsDir = "C:/data/chips")

# Fill single-class chips with a large sentinel instead of 0
makeBoundaryDistance(chipsDir = "C:/data/chips", noDataValue = 999)
} # }