geotrellis.raster.TileExtents.scala Maven / Gradle / Ivy

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/*
 * Copyright (c) 2014 Azavea.
 *
 * Licensed 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.
 */

package geotrellis.raster

import geotrellis._
import geotrellis.vector.Extent


/**
  * The [[TileExtents]] type.
  */
case class TileExtents(extent: Extent, tileLayout: TileLayout) {
  val cellSize = tileLayout.cellSize(extent)

  /**
    * Take a column and a row and produce an [[Extent]].
    */
  def apply(tileCol: Int, tileRow: Int): Extent = {
    Extent(
      xCoord(tileCol),
      yCoord(tileRow + 1),
      xCoord(tileCol + 1),
      yCoord(tileRow)
    )
  }

  /**
    * Take a tile index, relative to the [[TileLayout]] that was used
    * to create the present [[TileExtents]] object, and use that to
    * produce an [[Extent]].
    */
  def apply(tileIndex: Int): Extent = {
    val row = tileIndex / tileLayout.layoutCols
    val col = tileIndex - (row * tileLayout.layoutCols)
    apply(col, row)
  }

  /**
    * Given an extent and resolution (RasterExtent), return the
    * geographic X-coordinates for each tile boundary in this raster
    * data. For example, if we have a 2x2 ArrayTile, with a raster
    * extent whose X coordinates span 13.0 - 83.0 (i.e. cellwidth is
    * 35.0), we would return the following for the corresponding
    * input:
    *
    *  Input     Output
    * -------   --------
    *    0        13.0
    *    1        48.0
    *    2        83.0
    *
    */
  private def xCoord(col: Int): Double =
    extent.xmin + (col * cellSize.width * tileLayout.tileCols)

  /**
    * This method is identical to getXCoord except that it functions
    * on the Y-axis instead.
    *
    * Note that the origin tile (0, 0) is in the upper left of the
    * extent, so the upper left corner of the origin tile is (xmin,
    * ymax).
    */
  private def yCoord(row: Int): Double =
    extent.ymax - (row * cellSize.height * tileLayout.tileRows)
}