Remove Restriction to StreamingHistogram

The various histogram equalization functionality had previously been
tied to StreamingHistogram, now it works with Histogram[T].

raster/src/main/scala/geotrellis/raster/equalization/HistogramEqualization.scala

@@ -1,6 +1,7 @@
 package geotrellis.raster.equalization
 
 import geotrellis.raster._
+import geotrellis.raster.histogram.Histogram
 import geotrellis.raster.histogram.StreamingHistogram
 
 
@@ -74,14 +75,14 @@ object HistogramEqualization {
   }
 
   /**
-    * Given a [[Tile]] and a [[StreamingHistogram]], return a Tile
-    * with an equalized histogram.
+    * Given a [[Tile]] and a [[Histogram]], return a Tile with an
+    * equalized histogram.
     *
     * @param  tile       A singleband tile
     * @param  histogram  The histogram of the tile
     * @return            A singleband tile with improved contrast
     */
-  def apply(tile: Tile, histogram: StreamingHistogram): Tile = {
+  def apply[T <: AnyVal](tile: Tile, histogram: Histogram[T]): Tile = {
     val T = _T(tile.cellType, histogram.cdf)_
     tile.mapDouble(T)
   }
@@ -99,15 +100,15 @@ object HistogramEqualization {
   }
 
   /**
-    * Given a [[MultibandTile]] and a [[StreamingHistogram]] for each
-    * of its bands, return a MultibandTile whose bands all have
-    * equalized histograms.
+    * Given a [[MultibandTile]] and a [[Histogram]] for each of its
+    * bands, return a MultibandTile whose bands all have equalized
+    * histograms.
     *
     * @param  tile        A multiband tile
     * @param  histograms  A sequence of histograms, one for each band
     * @return             A multiband tile with improved contrast
     */
-  def apply(tile: MultibandTile, histograms: Seq[StreamingHistogram]): MultibandTile = {
+  def apply[T <: AnyVal](tile: MultibandTile, histograms: Seq[Histogram[T]]): MultibandTile = {
     MultibandTile(
       tile.bands
         .zip(histograms)

raster/src/main/scala/geotrellis/raster/histogram/FastMapHistogram.scala

@@ -310,6 +310,18 @@ class FastMapHistogram(_size: Int, _buckets: Array[Int], _counts: Array[Long], _
       None
   }
 
+  /**
+    * CDF of the distribution.
+    */
+  def cdf(): Array[(Double, Double)] = {
+    val pdf = counts.map({ n => (n / total.toDouble) })
+
+    buckets
+      .map({ label => label.toDouble })
+      .zip(pdf.scanLeft(0.0)(_ + _).drop(1))
+      .toArray
+  }
+
   /**
     * Return the smallest and largest values seen by the histogram, if
     * it has seen any values.

raster/src/main/scala/geotrellis/raster/histogram/Histogram.scala

@@ -44,6 +44,11 @@ abstract trait Histogram[@specialized (Int, Double) T <: AnyVal] extends Seriali
    */
   def maxValue(): Option[T]
 
+  /**
+    * CDF of the distribution.
+    */
+  def cdf(): Array[(Double, Double)]
+
   /**
    * Return the smallest and largest items seen as a tuple.
    */

spark/src/main/scala/geotrellis/spark/equalization/RDDHistogramEqualization.scala

@@ -2,6 +2,7 @@ package geotrellis.spark.equalization
 
 import geotrellis.raster._
 import geotrellis.raster.equalization.HistogramEqualization
+import geotrellis.raster.histogram.Histogram
 import geotrellis.raster.histogram.StreamingHistogram
 import geotrellis.spark._
 
@@ -35,16 +36,16 @@ object RDDHistogramEqualization {
   }
 
   /**
-    * Given an RDD of [[Tile]] objects and a [[StreamingHistogram]]
-    * derived from all of the tiles, return another RDD of tiles where
-    * the respective tiles have had their histograms equalized.
+    * Given an RDD of [[Tile]] objects and a [[Histogram]] derived
+    * from all of the tiles, return another RDD of tiles where the
+    * respective tiles have had their histograms equalized.
     *
     * @param  rdd        An RDD of tile objects
     * @param  histogram  A histogram derived from the whole RDD of tiles
     */
-  def singleband[K, V: (? => Tile): ClassTag, M](
+  def singleband[K, V: (? => Tile): ClassTag, M, T <: AnyVal](
     rdd: RDD[(K, V)] with Metadata[M],
-    histogram: StreamingHistogram
+    histogram: Histogram[T]
   ): RDD[(K, Tile)] with Metadata[M] = {
     ContextRDD(
       rdd.map({ case (key, tile: Tile) =>
@@ -70,23 +71,24 @@ object RDDHistogramEqualization {
           .map({ band => StreamingHistogram.fromTile(band, 1<<17) })
           .toArray })
       .reduce(r)
+      .map(_.asInstanceOf[Histogram[Double]])
 
     multiband(rdd, histograms)
   }
 
   /**
     * Given an RDD of [[MultibandTile]] objects and a sequence of
-    * [[StreamingHistogram]] objects (on per band) derived from all of
-    * the tiles, return another RDD of multiband tiles where the
+    * [[Histogram]] objects (on per band) derived from all of the
+    * tiles, return another RDD of multiband tiles where the
     * respective bands of the respective tiles have had their
     * histograms equalized.
     *
     * @param  rdd         An RDD of tile objects
     * @param  histograms  A histogram derived from the whole RDD of tiles
     */
-  def multiband[K, V: (? => MultibandTile): ClassTag, M](
+  def multiband[K, V: (? => MultibandTile): ClassTag, M, T <: AnyVal](
     rdd: RDD[(K, V)] with Metadata[M],
-    histograms: Array[StreamingHistogram]
+    histograms: Array[Histogram[T]]
   ): RDD[(K, MultibandTile)] with Metadata[M] = {
     ContextRDD(
       rdd.map({ case (key, tile: MultibandTile) =>

spark/src/main/scala/geotrellis/spark/equalization/RDDMultibandEqualizationMethods.scala

@@ -1,7 +1,7 @@
 package geotrellis.spark.equalization
 
 import geotrellis.raster._
-import geotrellis.raster.histogram.StreamingHistogram
+import geotrellis.raster.histogram.Histogram
 import geotrellis.spark._
 import geotrellis.util.MethodExtensions
 
@@ -25,6 +25,6 @@ trait RDDMultibandEqualizationMethods[K, M] extends MethodExtensions[RDD[(K, Mul
     *
     * @param  histograms  A sequence of histograms
     */
-  def equalize(histograms: Array[StreamingHistogram]): RDD[(K, MultibandTile)] with Metadata[M] =
+  def equalize[T <: AnyVal](histograms: Array[Histogram[T]]): RDD[(K, MultibandTile)] with Metadata[M] =
     RDDHistogramEqualization.multiband(self, histograms)
 }

spark/src/main/scala/geotrellis/spark/equalization/RDDSinglebandEqualizationMethods.scala

@@ -1,7 +1,7 @@
 package geotrellis.spark.equalization
 
 import geotrellis.raster._
-import geotrellis.raster.histogram.StreamingHistogram
+import geotrellis.raster.histogram.Histogram
 import geotrellis.spark._
 import geotrellis.util.MethodExtensions
 
@@ -24,6 +24,6 @@ trait RDDSinglebandEqualizationMethods[K, M] extends MethodExtensions[RDD[(K, Ti
     *
     * @param  histogram  A histogram
     */
-  def equalize(histogram: StreamingHistogram): RDD[(K, Tile)] with Metadata[M] =
+  def equalize[T <: AnyVal](histogram: Histogram[T]): RDD[(K, Tile)] with Metadata[M] =
     RDDHistogramEqualization.singleband(self, histogram)
 }