ConstantTile with nodata: support correct celltype conversion

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Dependecies update & fix "not found: type Serializable" compiler bug [#3535](https://github.com/locationtech/geotrellis/pull/3535)
 - Update GDAL up to 3.9.x [#3540](https://github.com/locationtech/geotrellis/pull/3540)
 - Fix reprojection with downsampling for GeotiffRasterSource and tile RDDs. Reprojection outside the valid projection bounds may now throw a GeoAttrsError. [#3541](https://github.com/locationtech/geotrellis/issues/3541)
+- ConstantTile: fix 'convert' method when the constant value is nodata. [#3525](https://github.com/locationtech/geotrellis/issues/3525)
 
 ## [3.7.1] - 2024-01-08
 

raster/src/main/scala/geotrellis/raster/ConstantTile.scala

@@ -19,7 +19,6 @@ package geotrellis.raster
 import geotrellis.vector.Extent
 
 import java.nio.ByteBuffer
-
 import spire.syntax.cfor._
 
 
@@ -83,6 +82,7 @@ abstract class ConstantTile extends Tile {
     */
   def convert(newType: CellType): Tile = {
     newType match {
+      case ct: CellType if  dVal.isNaN => ConstantTile.empty(newType, cols, rows)
       case BitCellType => new BitConstantTile(if (iVal == 0) false else true, cols, rows)
       case ct: ByteCells => ByteConstantTile(iVal.toByte, cols, rows, ct)
       case ct: UByteCells => UByteConstantTile(iVal.toByte, cols, rows, ct)
@@ -243,6 +243,45 @@ object ConstantTile {
       case ct: FloatCells => FloatConstantTile.fromBytes(bytes, cols, rows, ct)
       case ct: DoubleCells => DoubleConstantTile.fromBytes(bytes, cols, rows, ct)
     }
+
+  /**
+   * Create a [[ConstantTile]] that is set to the nodata value of the given celltype or to the default nodata value if
+   * the celltype does not have a nodata. BitCells are set to 'false'.
+   *
+   * @param   t      The [[CellType]] of the new [[ConstantTile]].
+   * @param   cols   The number of columns that the new [[ConstantTile]] should have
+   * @param   rows   The number of rows that the new [[ConstantTile]] should have
+   * @return         The new [[ConstantTile]]
+   */
+  def empty(t: CellType, cols: Int, rows: Int): Tile = {
+    t match {
+      case _: BitCells => BitConstantTile(false, cols, rows)
+      case ct: ByteUserDefinedNoDataCellType => ByteConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: ByteConstantNoDataCellType.type => ByteConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: ByteCellType.type => ByteConstantTile(byteNODATA ,cols, rows, ct)
+      case ct: UByteConstantNoDataCellType.type => UByteConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: UByteUserDefinedNoDataCellType => UByteConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: UByteCellType.type => UByteConstantTile(ubyteNODATA ,cols, rows, ct)
+      case ct: ShortUserDefinedNoDataCellType => ShortConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: ShortConstantNoDataCellType.type => ShortConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: ShortCellType.type => ShortConstantTile(shortNODATA ,cols, rows, ct)
+      case ct: UShortUserDefinedNoDataCellType => UShortConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: UShortConstantNoDataCellType.type => UShortConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: UShortCellType.type => UShortConstantTile(ushortNODATA ,cols, rows, ct)
+      case ct: IntUserDefinedNoDataCellType => IntConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: IntConstantNoDataCellType.type => IntConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: IntCellType.type => IntConstantTile(NODATA ,cols, rows, ct)
+      case ct: FloatUserDefinedNoDataCellType => FloatConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: FloatConstantNoDataCellType.type => FloatConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: FloatCellType.type => FloatConstantTile(floatNODATA ,cols, rows, ct)
+      case ct: DoubleUserDefinedNoDataCellType => DoubleConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: DoubleConstantNoDataCellType.type => DoubleConstantTile(ct.noDataValue ,cols, rows, ct)
+      case ct: DoubleCellType.type => DoubleConstantTile(doubleNODATA ,cols, rows, ct)
+    }
+  }
+
+
+
 }
 
 /**

raster/src/test/scala/geotrellis/raster/ConstantTileSpec.scala

@@ -93,4 +93,30 @@ class ConstantTileSpec extends AnyFunSpec with Matchers with RasterMatchers with
       int.combine(dt)(_ + _).cellType shouldBe int.cellType.union(dt.cellType)
     }
   }
+
+  describe("celltype conversion") {
+    it("should convert ByteConstantTile with nodata") {
+      val t = ByteConstantTile(byteNODATA, cols = 1, rows = 1)
+      assert(t.isNoDataTile)
+      assert(t.convert(t.cellType).isNoDataTile)
+    }
+
+    it("should convert ByteConstantTile") {
+      val t = ByteConstantTile(10, cols = 1, rows = 1)
+      assert(t.convert(FloatConstantNoDataCellType).getDouble(0,0) === 10.0)
+    }
+
+    it("should convert empty IntConstantTile ") {
+      val t = ConstantTile.empty(IntCellType, 1, 1)
+      assert(t.isNoDataTile)
+      assert(t.convert(IntUserDefinedNoDataCellType(3)).isNoDataTile)
+    }
+
+    it("should convert empty FloatConstantTile ") {
+      val t = ConstantTile.empty(FloatCellType, 1, 1)
+      assert(t.isNoDataTile)
+      val converted: Tile = t.convert(FloatUserDefinedNoDataCellType(3.0f))
+      assert(converted.isNoDataTile)
+    }
+  }
 }