Package 'grout'

Create a tiling scheme from a raster

Description

The input may be an actual raster or a matrix. There is an assumed block size of 256x256, and the scheme will record the number of tiles in each dimension and the amount of "overlapping dangle" when the dimensions of the data don't fit neatly within the tiles.

Usage

grout(dimension, extent = NULL, blocksize = NULL, projection = NA_character_)

Arguments

dimension	number of columns and rows of the raster grid
extent	extent of the raster grid xmin,xmax,ymin,ymax
blocksize	tile dimensions in columns (X) and rows (Y)
projection	the projection (crs) of the grid

Details

If extent is not provided the default 'xmin=0,xmax=ncol,ymin=0,ymax=nrow' is used.

The tile scheme object has print and plot methods for basic information.

See example in the README with 'wk::rct' to generate plot-able and efficient spatial objects from the scheme.

Value

A "tile scheme" object with information about the tile spacing and extent.

Examples

## one block tile (too big)
grout(c(87, 61), blocksize = c(256L, 256L))
## more size appropriate
grout(c(87, 61), blocksize = c(8, 8))
grout(c(10, 20), c(0, 1, 0, 2), blocksize = c(256, 256))

---

plot tiles

Description

plot tiles

Usage

## S3 method for class 'grout_tiles'
plot(x, ..., add = FALSE, border = "grey", lwd = 2)

Arguments

x	a grout [tiles()] object
...	arguments passed to methods
add	add to current plot or start a new one (default is 'FALSE', a new plot)
border	the colour of the tile border (default grey)
lwd	the width of the tile border (default = 2)

---

print tiles

Description

print tiles

Usage

## S3 method for class 'grout_tiles'
print(x, ...)

Arguments

x	a grout [tiles()] object
...	ignored

---

Tile index

Description

Generate a table of tile indexes from a tiling object.

Usage

tile_index(x)

Arguments

x	tiling object, created by [tiles()]

Details

A data frame with

* **tile** - index, same as raster cell number * **offset_x** - column offset of tile (index column 0-based) * **offset_y** - row offset of tile (index row 0-based, relative to top row) * **ncol** number of columns in tile (the right and bottom margins may have a dangle based on block size) * **nrow** number of rows in th tile * xmin, xmax, ymin, ymax - the exent

Note that ncol,nrow is the block size *unless* the tile is part of a dangling column or row (right or bottom) where the raster doesn't fill complete tiles.

Value

data frame, see details

Examples

tile_index(grout(c(87, 61), extent = c(0, 1, 0, 1), blocksize = c(32, 16)))
## only one tile in this weird scheme!
tile_index(grout(c(61, 87), blocksize = c(61, 87)))

---

Create tile specification

Description

Take an input grid (dimension and extent) and create a specification of the tiling for that grid within a profile.

Usage

tile_spec(
  dimension,
  extent,
  zoom = 0,
  blocksize = c(256L, 256L),
  profile = c("mercator", "geodetic", "raster"),
  crs = NA,
  xyz = FALSE
)

tile_zoom(
  dimension,
  extent,
  blocksize = c(256L, 256L),
  profile = c("mercator", "geodetic", "raster")
)

Arguments

dimension	size in pixels ncol,nrow
extent	xmin,xmax,ymin,ymax
zoom	the zoom level, starts at 0 and can be up to 24
blocksize	size of each tile, defaults to 256x256
profile	profile domain to use, see Details
crs	crs, for raster profile
xyz	default is 'FALSE', if 'TRUE' use xyz-mode (zero is at the top)

Details

Profiles are 'mercator' or "geodetic" for global systems, or can use "raster" which will use the input grid specification as the entire domain.

'tile_row' in output is in TMS orientation (zero is at the bottom), use 'xyz' arg to switch.

Function 'tile_zoom()' will return the "natural" maximum zoom level, i.e. the zoom at which the tile resolution is just below the input resolution. Note that no reprojection is done, the input extent must match the profile chosen (use 'raster' for native profile).

Value

data frame with tile specification, tile index, tile_col, tile_row, ncol, nrow, xmin, xmax, ymin, ymax, crs

Examples

tile_spec(c(8194, 8194), c(140, 155, -45, -30), profile = "geodetic")

tile_spec(c(2048, 248), c(140, 155, -45, -30), zoom = 5, profile = "geodetic", 
   blocksize = c(512, 512))

---