Use zarr string fill values (#7017)

Author: frcroth

CHANGELOG.unreleased.md

@@ -18,6 +18,7 @@ For upgrade instructions, please check the [migration guide](MIGRATIONS.released
 
 ### Fixed
 - Fixed that changing a segment color could lead to a crash. [#7000](https://github.com/scalableminds/webknossos/pull/7000)
+- The fill_value property of zarr dataset is now used when it is not a number. [#7017](https://github.com/scalableminds/webknossos/pull/7017)
 - Fixed rendering issues on some affected systems that led to "black holes". [#7018](https://github.com/scalableminds/webknossos/pull/7018)
 - Fixed a bug that made downloads of public annotations fail occasionally. [#7025](https://github.com/scalableminds/webknossos/pull/7025)
 - Added a workaround for a WebGL crash which could appear when a dataset contained many segmentation layers. [#6995](https://github.com/scalableminds/webknossos/pull/6995)

webknossos-datastore/app/com/scalableminds/webknossos/datastore/datareaders/ArrayDataType.scala

@@ -19,4 +19,32 @@ object ArrayDataType extends ExtendedEnumeration {
       case ArrayDataType.i1 => 1
       case ArrayDataType.u1 => 1
     }
+
+  def maxValue(dataType: ArrayDataType): Number =
+    dataType match {
+      case ArrayDataType.f8 => Double.MaxValue
+      case ArrayDataType.f4 => Float.MaxValue
+      case ArrayDataType.i8 => Long.MaxValue
+      case ArrayDataType.u8 => Long.MaxValue // Max value for primitive datatypes
+      case ArrayDataType.i4 => Int.MaxValue
+      case ArrayDataType.u4 => Math.pow(2, 4 * 8).toLong - 1
+      case ArrayDataType.i2 => Char.MaxValue
+      case ArrayDataType.u2 => Math.pow(2, 2 * 8).toLong - 1
+      case ArrayDataType.i1 => Byte.MaxValue
+      case ArrayDataType.u1 => Math.pow(2, 1 * 8).toLong - 1
+    }
+
+  def minValue(dataType: ArrayDataType): Number =
+    dataType match {
+      case ArrayDataType.f8 => Double.MinValue
+      case ArrayDataType.f4 => Float.MinValue
+      case ArrayDataType.i8 => Long.MinValue
+      case ArrayDataType.u8 => 0
+      case ArrayDataType.i4 => Int.MinValue
+      case ArrayDataType.u4 => 0
+      case ArrayDataType.i2 => Char.MinValue
+      case ArrayDataType.u2 => 0
+      case ArrayDataType.i1 => Byte.MinValue
+      case ArrayDataType.u1 => 0
+    }
 }

webknossos-datastore/app/com/scalableminds/webknossos/datastore/datareaders/DatasetHeader.scala

@@ -33,7 +33,7 @@ trait DatasetHeader {
   lazy val fillValueNumber: Number =
     fill_value match {
       case Right(n) => n
-      case Left(_)  => 0 // parsing fill value from string not currently supported
+      case Left(s)  => parseFillValueFromString(s)
     }
 
   def boundingBox(axisOrder: AxisOrder): Option[BoundingBox] =
@@ -48,5 +48,13 @@ trait DatasetHeader {
 
   def isSharded = false
 
+  private def parseFillValueFromString(s: String): Number =
+    s match {
+      case "NaN"       => 0
+      case "Infinity"  => ArrayDataType.maxValue(resolvedDataType)
+      case "-Infinity" => ArrayDataType.minValue(resolvedDataType)
+      case _           => 0 // Unsupported fill value does not throw exception
+    }
+
   def voxelOffset: Array[Int]
 }