james-willis commented on code in PR #1065: URL: https://github.com/apache/sedona-db/pull/1065#discussion_r3668641798
########## docs/reference/sql/rs_tile.qmd: ########## @@ -0,0 +1,130 @@ +--- +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you under the Apache License, Version 2.0 (the +# "License"); you may not use this file except in compliance +# with the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, +# software distributed under the License is distributed on an +# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +# KIND, either express or implied. See the License for the +# specific language governing permissions and limitations +# under the License. + +title: RS_Tile +description: > + Returns an array of rasters resulting from the split of the input raster into + a grid of fixed-size tiles, one list item per tile with its grid position. +kernels: + - returns: list + args: + - raster + - name: width + type: integer + description: Tile width in pixels. Must be >= 1. + - name: height + type: integer + description: Tile height in pixels. Must be >= 1. + - name: pad_with_no_data + type: boolean + description: > + Optional (default false). When true, pad the last partial row/column of + tiles to the full tile size with a nodata fill; when false the smaller + edge tile is emitted as-is. + - name: no_data_val + type: double + description: > + Optional. The value written to padded pixels (only valid with + `pad_with_no_data = true`); defaults to the band's own nodata value, or + the band data type's minimum if it has none. It is an error if it does + not fit the band's data type. + - returns: list + args: + - raster + - name: band_indices + type: array + description: > + `Array[Int]` of 1-based band indices to include in each tile, in the + given order. + - name: width + type: integer + description: Tile width in pixels. Must be >= 1. + - name: height + type: integer + description: Tile height in pixels. Must be >= 1. + - name: pad_with_no_data + type: boolean + description: Optional (default false). See the no-band overload. + - name: no_data_val + type: double + description: Optional. See the no-band overload. +--- + +::: callout-warning +**Experimental.** This function is experimental; its behavior may change without notice. +::: + +## Description + +`RS_Tile` cuts a raster into a grid of `width` x `height` tiles, returning a +list with one item per tile that you `UNNEST` to get one row per tile. + +It has two overloads (`padWithNoData` and `noDataVal` are trailing +optionals): + +- `RS_Tile(raster, width, height, padWithNoData = false, noDataVal = null)` +- `RS_Tile(raster, bandIndices, width, height, padWithNoData = false, noDataVal = null)` + +When no band argument is given, every band is included. `bandIndices` selects +an ordered subset of bands. Band indices are 1-based. + +Each returned list item is a struct with: + +- `x`: the tile's grid column (0-based), counting from the left +- `y`: the tile's grid row (0-based), counting from the top +- `tile`: the tile raster, with a geotransform shifted to the tile's own origin + +The grid is `ceil(width / tile_width)` columns by `ceil(height / tile_height)` +rows. When the raster does not divide evenly, the last column and row of tiles +are partial: with `padWithNoData = false` the smaller edge tile is emitted +as-is, and with `padWithNoData = true` those tiles are padded to the full tile +size with a nodata fill. When the band(s) have no nodata value, `noDataVal` +supplies one. + +::: callout-note +`RS_Tile` **copies the raster**: every tile carries its own pixels, so the +returned list materializes a full copy of the raster spread across the tiles and +held in memory as one list value. A small tile size produces many tiles (a +`1 x 1` tile size yields one tile per pixel). +::: Review Comment: yeah. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
