geotrellis.raster.resample.ModeResample.scala Maven / Gradle / Ivy

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GeoTrellis is an open source geographic data processing engine for high performance applications.

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package geotrellis.raster.resample

import geotrellis.raster._
import geotrellis.raster.summary._
import geotrellis.raster.histogram._
import geotrellis.vector.Extent

import scala.collection.mutable
import collection._

import spire.syntax.cfor._

/**
  * Takes the most common value in a region and resamples to that.
  *
  * As with other aggregate resampling methods, this is most useful when
  * decreasing resolution or downsampling.
  *
  */
class ModeResample(tile: Tile, extent: Extent, targetCS: CellSize)
    extends AggregateResample(tile, extent, targetCS) {

  private def calculateIntMode(indices: Seq[(Int, Int)]): Int = {
    val values = indices.foldLeft(mutable.Map[Int, Int]()) { (hash, coords) =>
      val v = tile.get(coords._1, coords._2)
      hash(v) = hash.getOrElseUpdate(v, 0) + 1
      hash
    }.toSeq
    if (values.size > 0) values.maxBy { case (key, value) => value }._1
    else NODATA
  }

  private def calculateDoubleMode(indices: Seq[(Int, Int)]): Double = {
    val values = indices.foldLeft(mutable.Map[Double, Int]()) { (hash, coords) =>
      val v = tile.getDouble(coords._1, coords._2)
      hash(v) = hash.getOrElseUpdate(v, 0) + 1
      hash
    }.toSeq
    if (values.size > 0) values.maxBy { case (key, value) => value }._1
    else Double.NaN
  }

  def resampleValid(x: Double, y: Double): Int =
    calculateIntMode(contributions(x, y))

  def resampleDoubleValid(x: Double, y: Double): Double =
    calculateDoubleMode(contributions(x, y))
}