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• 0.9.2
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• ZonalHistograms.scala

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geotrellis.raster.op.zonal.ZonalHistograms.scala Maven / Gradle / Ivy

package geotrellis.raster.op.zonal

import geotrellis._
import geotrellis.process._
import geotrellis.statistics._

import spire.syntax.cfor._

import scala.collection.mutable

/**
 * Given a raster, return a histogram summary of the cells within each zone.
 *
 * @note    ZonalHistogram does not currently support Double raster data.
 *          If you use a Raster with a Double RasterType (TypeFloat,TypeDouble)
 *          the data values will be rounded to integers.
 */
case class ZonalHistogram(data: Op[Raster], zones: Op[Raster]) 
     extends Op2(data, zones) ({
  (raster, zones) => {
    val histMap = mutable.Map[Int,FastMapHistogram]()

    val rows  = raster.rasterExtent.rows
    val cols  = raster.rasterExtent.cols

    cfor(0)(_ < rows, _ + 1) { row =>
      cfor(0)(_ < cols, _ + 1) { col =>
        val v = raster.get(col,row)
        val z = zones.get(col,row)
        if(!histMap.contains(z)) { histMap(z) = FastMapHistogram() }
        histMap(z).countItem(v)
      }
    }

    Result(histMap.toMap)
  }
})