Shrink the valid-data footprint by a pixel margin.

Sets to NaN every pixel within radius pixels of nodata, eroding each nodata boundary (scene footprint edges, cloud-mask holes, the raster border) by that margin. The standard cure for corrupt scene edges: satellite granules commonly carry one or two pixels of bad radiometry just inside their data footprint that QA masks miss, and on a (t, y, x) stack each slice's footprint erodes independently.

Usage

shrink_footprint(x, radius = 1L, bands = NULL)

Arguments

x

A LazyRaster, or a LazyDataset.

radius

Margin to remove, in pixels.

bands

LazyDataset only: bands to apply to (default: all value bands).

Value

The eroded object, same class and grid as x.

Details

Implemented as a focal() kernel (centre plus zero times the window sum, which is NaN wherever any neighbour is NaN), so it plans and fuses like any stencil, and applies per band over a LazyDataset.