Gjallarhorn: Timelapse Mode

README.md

@@ -1,17 +1,25 @@
 # Foundation
+
 Foundation is a set of plugins that implement the core functionality for a small community Minecraft
 server.
 
 ## Plugins
-* foundation-core - Core functionality
-* foundation-bifrost - Discord chat bridge
-* foundation-heimdall - Event tracking
+
+* foundation-core: Core functionality
+* foundation-bifrost: Discord chat bridge
+* foundation-heimdall: Event tracking
+
+## Tools
+
+* tool-gjallarhorn - Heimdall swiss army knife
 
 ## Installation
+
 The following command downloads and runs a script that will fetch the latest update manifest, and
 install all plugins available. It can also be used to update plugins to the latest version
 available.
-```
+
+```bash
 # Always validate the contents of a script from the internet!
 bash -c "$(curl -sL https://git.gorence.io/lgorence/foundation/-/raw/main/install.sh)"
 ```

build.gradle.kts

@@ -10,6 +10,9 @@ plugins {
   id("com.github.johnrengelman.shadow") version "7.1.1" apply false
 }
 
+fun Project.isFoundationPlugin() = name.startsWith("foundation-")
+fun Project.isFoundationTool() = !isFoundationPlugin()
+
 // Disable the JAR task for the root project.
 tasks["jar"].enabled = false
 
@@ -39,7 +42,7 @@ tasks.create("updateManifests") {
     writer.use {
       val rootPath = rootProject.rootDir.toPath()
       val updateManifest = subprojects.mapNotNull { project ->
-        if (project.name == "foundation-gjallarhorn") {
+        if (project.isFoundationTool()) {
           return@mapNotNull null
         }
         val files = project.tasks.getByName("shadowJar").outputs
@@ -122,7 +125,7 @@ subprojects {
     }
   }
 
-  if (project.name != "foundation-gjallarhorn") {
+  if (project.isFoundationTool()) {
     tasks.withType<ShadowJar> {
       archiveClassifier.set("plugin")
     }

foundation-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/BlockOffset.kt

@@ -1,17 +0,0 @@
-package cloud.kubelet.foundation.gjallarhorn
-
-data class BlockOffset(
-  val x: Long,
-  val y: Long,
-  val z: Long
-) {
-  fun apply(position: BlockPosition) = position.copy(
-    x = position.x + x,
-    y = position.y + y,
-    z = position.z + z
-  )
-
-  companion object {
-    val none = BlockOffset(0, 0, 0)
-  }
-}

foundation-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/BlockPosition.kt

@@ -1,19 +0,0 @@
-package cloud.kubelet.foundation.gjallarhorn
-
-import java.util.*
-
-data class BlockPosition(
-  val x: Long,
-  val y: Long,
-  val z: Long
-) {
-  override fun equals(other: Any?): Boolean {
-    if (other !is BlockPosition) {
-      return false
-    }
-
-    return other.x == x && other.y == y && other.z == z
-  }
-
-  override fun hashCode(): Int = Objects.hash(x, y, z)
-}

foundation-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/commands/BlockLogReplay.kt

@@ -1,81 +0,0 @@
-package cloud.kubelet.foundation.gjallarhorn.commands
-
-import cloud.kubelet.foundation.gjallarhorn.*
-import cloud.kubelet.foundation.gjallarhorn.util.savePngFile
-import cloud.kubelet.foundation.heimdall.view.BlockChangeView
-import com.github.ajalt.clikt.core.CliktCommand
-import com.github.ajalt.clikt.core.requireObject
-import com.github.ajalt.clikt.parameters.options.flag
-import com.github.ajalt.clikt.parameters.options.option
-import org.jetbrains.exposed.sql.Database
-import org.jetbrains.exposed.sql.SqlExpressionBuilder.lessEq
-import org.jetbrains.exposed.sql.and
-import org.jetbrains.exposed.sql.select
-import org.jetbrains.exposed.sql.transactions.transaction
-import java.time.Instant
-import java.util.concurrent.atomic.AtomicLong
-
-class BlockLogReplay : CliktCommand("Replay Block Logs", name = "replay-block-log") {
-  private val db by requireObject<Database>()
-  private val timeAsString by option("--time", help = "Replay Time")
-  private val renderTopDown by option("--render-top-down", help = "Render TOp Down Image").flag()
-  private val renderHeightMap by option("--render-height-map", help = "Render Height Map Image").flag()
-
-  private val considerAirBlocks by option("--consider-air-blocks", help = "Enable Air Block Consideration").flag()
-
-  override fun run() {
-    val filter = compose(
-      combine = { a, b -> a and b },
-      { timeAsString != null } to { BlockChangeView.time lessEq Instant.parse(timeAsString) }
-    )
-    val tracker =
-      BlockStateTracker(if (considerAirBlocks) BlockTrackMode.AirOnDelete else BlockTrackMode.RemoveOnDelete)
-
-    val blockChangeCounter = AtomicLong()
-    transaction(db) {
-      BlockChangeView.select(filter).orderBy(BlockChangeView.time).forEach { row ->
-        val changeIsBreak = row[BlockChangeView.isBreak]
-        val x = row[BlockChangeView.x]
-        val y = row[BlockChangeView.y]
-        val z = row[BlockChangeView.z]
-        val block = row[BlockChangeView.block]
-
-        val location = BlockPosition(x.toLong(), y.toLong(), z.toLong())
-        if (changeIsBreak) {
-          tracker.delete(location)
-        } else {
-          tracker.place(location, BlockState(block))
-        }
-
-        val count = blockChangeCounter.addAndGet(1)
-        if (count % 1000L == 0L) {
-          System.err.println("Calculating Block Changes... $count")
-        }
-      }
-    }
-    System.err.println("Total Block Changes... ${blockChangeCounter.get()}")
-
-    val uniqueBlockPositions = tracker.blocks.size
-    System.err.println("Unique Block Positions... $uniqueBlockPositions")
-
-    val blockZeroOffset = tracker.calculateZeroBlockOffset()
-    System.err.println("Zero Block Offset... $blockZeroOffset")
-
-    if (renderTopDown) {
-      val image = BlockStateImage()
-      tracker.populate(image, offset = blockZeroOffset)
-      val bufferedImage = image.buildTopDownImage()
-      bufferedImage.savePngFile("top-down.png")
-    } else if (renderHeightMap) {
-      val image = BlockStateImage()
-      tracker.populate(image, offset = blockZeroOffset)
-      val bufferedImage = image.buildHeightMapImage()
-      bufferedImage.savePngFile("height-map.png")
-    } else {
-      println("x,y,z,block")
-      for ((position, block) in tracker.blocks) {
-        println("${position.x},${position.y},${position.z},${block.type}")
-      }
-    }
-  }
-}

foundation-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/util/ImageTools.kt

@@ -1,7 +0,0 @@
-package cloud.kubelet.foundation.gjallarhorn.util
-
-import java.awt.image.BufferedImage
-import java.io.File
-import javax.imageio.ImageIO
-
-fun BufferedImage.savePngFile(path: String) = ImageIO.write(this, "png", File(path))

foundation-heimdall/src/main/kotlin/cloud/kubelet/foundation/heimdall/event/BlockPlace.kt

@@ -1,7 +1,6 @@
 package cloud.kubelet.foundation.heimdall.event
 
 import cloud.kubelet.foundation.heimdall.storageBlockName
-import cloud.kubelet.foundation.heimdall.table.BlockBreakTable
 import cloud.kubelet.foundation.heimdall.table.BlockPlaceTable
 import org.bukkit.Location
 import org.bukkit.Material
@@ -22,15 +21,15 @@ class BlockPlace(
   override fun store(transaction: Transaction) {
     transaction.apply {
       BlockPlaceTable.insert {
-        it[BlockBreakTable.time] = timestamp
-        it[BlockBreakTable.player] = playerUniqueIdentity
-        it[BlockBreakTable.world] = location.world.uid
-        it[BlockBreakTable.x] = location.x
-        it[BlockBreakTable.y] = location.y
-        it[BlockBreakTable.z] = location.z
-        it[BlockBreakTable.pitch] = location.pitch.toDouble()
-        it[BlockBreakTable.yaw] = location.yaw.toDouble()
-        it[BlockBreakTable.block] = material.storageBlockName
+        it[time] = timestamp
+        it[player] = playerUniqueIdentity
+        it[world] = location.world.uid
+        it[x] = location.x
+        it[y] = location.y
+        it[z] = location.z
+        it[pitch] = location.pitch.toDouble()
+        it[yaw] = location.yaw.toDouble()
+        it[block] = material.storageBlockName
       }
     }
   }

settings.gradle.kts

@@ -4,5 +4,5 @@ include(
   ":foundation-core",
   ":foundation-bifrost",
   ":foundation-heimdall",
-  ":foundation-gjallarhorn",
+  ":tool-gjallarhorn",
 )

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/GjallarhornCommand.kt

@@ -12,7 +12,7 @@ class GjallarhornCommand : CliktCommand(invokeWithoutSubcommand = true) {
   private val jdbcConnectionUsername by option("-u", "--connection-username", help = "JDBC Connection Username")
     .default("jdbc:postgresql://localhost/foundation")
 
-  private val jdbcConnectionPassword by option("-p", "--connection-password", help = "JDBC Connection Passowrd")
+  private val jdbcConnectionPassword by option("-p", "--connection-password", help = "JDBC Connection Password")
     .default("jdbc:postgresql://localhost/foundation")
 
   override fun run() {

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/commands/BlockLogReplay.kt

@@ -0,0 +1,130 @@
+package cloud.kubelet.foundation.gjallarhorn.commands
+
+import cloud.kubelet.foundation.gjallarhorn.compose
+import cloud.kubelet.foundation.gjallarhorn.render.*
+import cloud.kubelet.foundation.gjallarhorn.util.savePngFile
+import cloud.kubelet.foundation.heimdall.view.BlockChangeView
+import com.github.ajalt.clikt.core.CliktCommand
+import com.github.ajalt.clikt.core.requireObject
+import com.github.ajalt.clikt.parameters.options.flag
+import com.github.ajalt.clikt.parameters.options.option
+import com.github.ajalt.clikt.parameters.options.required
+import com.github.ajalt.clikt.parameters.types.enum
+import jetbrains.exodus.kotlin.notNull
+import org.jetbrains.exposed.sql.*
+import org.jetbrains.exposed.sql.SqlExpressionBuilder.lessEq
+import org.jetbrains.exposed.sql.transactions.transaction
+import org.slf4j.LoggerFactory
+import java.awt.image.BufferedImage
+import java.time.Duration
+import java.time.Instant
+import java.util.concurrent.atomic.AtomicLong
+
+class BlockLogReplay : CliktCommand("Replay Block Logs", name = "replay-block-log") {
+  private val db by requireObject<Database>()
+  private val exactTimeAsString by option("--time", help = "Replay Time")
+  private val timeLapseMode by option("--timelapse", help = "Timelapse Mode").enum<TimeLapseMode> { it.id }
+  private val render by option("--render", help = "Render Top Down Image").enum<RenderType> { it.id }.required()
+
+  private val considerAirBlocks by option("--consider-air-blocks", help = "Enable Air Block Consideration").flag()
+
+  private val logger = LoggerFactory.getLogger(BlockLogReplay::class.java)
+
+  override fun run() {
+    if (timeLapseMode != null) {
+      val (start, end) = transaction(db) {
+        val minTimeColumn = BlockChangeView.time.min().notNull
+        val maxTimeColumn = BlockChangeView.time.max().notNull
+        val row = BlockChangeView.slice(minTimeColumn, maxTimeColumn).selectAll().single()
+        row[minTimeColumn]!! to row[maxTimeColumn]!!
+      }
+
+      val intervals = mutableListOf<Instant>()
+      var current = start
+      while (!current.isAfter(end)) {
+        intervals.add(current)
+        current = current.plus(timeLapseMode!!.interval)
+      }
+
+      val trackers = mutableMapOf<Int, BlockStateTracker>()
+      for (time in intervals) {
+        val index = intervals.indexOf(time) + 1
+        val tracker = buildTrackerState(time, "Timelapse-${index}")
+        if (tracker.isEmpty()) {
+          continue
+        }
+        trackers[index] = tracker
+      }
+
+      val allBlockOffsets = trackers.map { it.value.calculateZeroBlockOffset() }
+      val globalBlockOffset = BlockPosition.maxOf(allBlockOffsets.asSequence())
+      val allBlockMaxes = trackers.map { it.value.calculateZeroBlockOffset() }
+      val globalBlockMax = BlockPosition.maxOf(allBlockMaxes.asSequence())
+      val globalBlockExpanse = BlockExpanse.offsetAndMax(globalBlockOffset, globalBlockMax)
+
+      for ((i, tracker) in trackers.entries) {
+        saveRenderImage(tracker, globalBlockExpanse, "-${i}")
+      }
+    } else {
+      val time = if (exactTimeAsString != null) Instant.parse(exactTimeAsString) else null
+      val tracker = buildTrackerState(time, "Single-Time")
+      val expanse = BlockExpanse.offsetAndMax(tracker.calculateZeroBlockOffset(), tracker.calculateMaxBlock())
+      saveRenderImage(tracker, expanse)
+    }
+  }
+
+  fun saveRenderImage(tracker: BlockStateTracker, expanse: BlockExpanse, suffix: String = "") {
+    val state = BlockStateImage()
+    tracker.populateStateImage(state, expanse.offset)
+    val image = render.renderBufferedImage(state, expanse)
+    image.savePngFile("${render.id}${suffix}.png")
+  }
+
+  fun buildTrackerState(time: Instant?, job: String): BlockStateTracker {
+    val filter = compose(
+      combine = { a, b -> a and b },
+      { time != null } to { BlockChangeView.time lessEq time!! }
+    )
+
+    val tracker =
+      BlockStateTracker(if (considerAirBlocks) BlockTrackMode.AirOnDelete else BlockTrackMode.RemoveOnDelete)
+
+    val blockChangeCounter = AtomicLong()
+    transaction(db) {
+      BlockChangeView.select(filter).orderBy(BlockChangeView.time).forEach { row ->
+        val changeIsBreak = row[BlockChangeView.isBreak]
+        val x = row[BlockChangeView.x]
+        val y = row[BlockChangeView.y]
+        val z = row[BlockChangeView.z]
+        val block = row[BlockChangeView.block]
+
+        val location = BlockPosition(x.toLong(), y.toLong(), z.toLong())
+        if (changeIsBreak) {
+          tracker.delete(location)
+        } else {
+          tracker.place(location, BlockState(block))
+        }
+
+        val count = blockChangeCounter.addAndGet(1)
+        if (count % 1000L == 0L) {
+          logger.info("Job $job Calculating Block Changes... $count")
+        }
+      }
+    }
+    logger.info("Job $job Total Block Changes... ${blockChangeCounter.get()}")
+
+    val uniqueBlockPositions = tracker.blocks.size
+    logger.info("Job $job Unique Block Positions... $uniqueBlockPositions")
+    return tracker
+  }
+
+  enum class RenderType(val id: String, val renderBufferedImage: (BlockStateImage, BlockExpanse) -> BufferedImage) {
+    TopDown("top-down", { image, expanse -> image.buildTopDownImage(expanse) }),
+    HeightMap("height-map", { image, expanse -> image.buildHeightMapImage(expanse) })
+  }
+
+  enum class TimeLapseMode(val id: String, val interval: Duration) {
+    ByHour("hours", Duration.ofHours(1)),
+    ByDay("days", Duration.ofDays(1))
+  }
+}

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/commands/PlayerSessionExport.kt

@@ -1,5 +1,6 @@
-package cloud.kubelet.foundation.gjallarhorn
+package cloud.kubelet.foundation.gjallarhorn.commands
 
+import cloud.kubelet.foundation.gjallarhorn.compose
 import cloud.kubelet.foundation.heimdall.table.PlayerSessionTable
 import com.github.ajalt.clikt.core.CliktCommand
 import com.github.ajalt.clikt.core.requireObject

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/main.kt

@@ -2,6 +2,7 @@ package cloud.kubelet.foundation.gjallarhorn
 
 import cloud.kubelet.foundation.gjallarhorn.commands.BlockLogReplay
 import cloud.kubelet.foundation.gjallarhorn.commands.PlayerPositionExport
+import cloud.kubelet.foundation.gjallarhorn.commands.PlayerSessionExport
 import com.github.ajalt.clikt.core.subcommands
 
 fun main(args: Array<String>) = GjallarhornCommand().subcommands(

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/render/BlockExpanse.kt

@@ -0,0 +1,13 @@
+package cloud.kubelet.foundation.gjallarhorn.render
+
+class BlockExpanse(
+  val offset: BlockPosition,
+  val size: BlockPosition
+) {
+  companion object {
+    fun offsetAndMax(offset: BlockPosition, max: BlockPosition) = BlockExpanse(
+      offset,
+      offset.applyAsOffset(max)
+    )
+  }
+}

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/render/BlockPosition.kt

@@ -0,0 +1,37 @@
+package cloud.kubelet.foundation.gjallarhorn.render
+
+import java.util.*
+
+data class BlockPosition(
+  val x: Long,
+  val y: Long,
+  val z: Long
+) {
+  override fun equals(other: Any?): Boolean {
+    if (other !is BlockPosition) {
+      return false
+    }
+
+    return other.x == x && other.y == y && other.z == z
+  }
+
+  override fun hashCode(): Int = Objects.hash(x, y, z)
+
+  fun applyAsOffset(position: BlockPosition) = position.copy(
+    x = position.x + x,
+    y = position.y + y,
+    z = position.z + z
+  )
+
+  companion object {
+    val zero = BlockPosition(0, 0, 0)
+
+    fun maxOf(positions: Sequence<BlockPosition>): BlockPosition {
+      val x = positions.maxOf { it.x }
+      val y = positions.maxOf { it.y }
+      val z = positions.maxOf { it.z }
+
+      return BlockPosition(x, y, z)
+    }
+  }
+}

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/render/BlockState.kt

@@ -1,4 +1,4 @@
-package cloud.kubelet.foundation.gjallarhorn
+package cloud.kubelet.foundation.gjallarhorn.render
 
 import kotlinx.serialization.Serializable
 

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/render/BlockStateImage.kt

@@ -1,4 +1,4 @@
-package cloud.kubelet.foundation.gjallarhorn
+package cloud.kubelet.foundation.gjallarhorn.render
 
 import cloud.kubelet.foundation.gjallarhorn.util.ColorGradient
 import cloud.kubelet.foundation.gjallarhorn.util.FloatClamp
@@ -18,9 +18,9 @@ class BlockStateImage {
     }[position.y] = state
   }
 
-  fun buildTopDownImage(): BufferedImage {
+  fun buildTopDownImage(expanse: BlockExpanse): BufferedImage {
     val colorKey = RandomColorKey()
-    return buildPixelQuadImage { x, z ->
+    return buildPixelQuadImage(expanse) { x, z ->
       val maybeYBlocks = blocks[x]?.get(z)
       if (maybeYBlocks == null) {
         setPixelQuad(x, z, Color.white.rgb)
@@ -37,16 +37,16 @@ class BlockStateImage {
     }
   }
 
-  fun buildHeightMapImage(): BufferedImage {
+  fun buildHeightMapImage(expanse: BlockExpanse): BufferedImage {
     val yMin = blocks.minOf { xSection -> xSection.value.minOf { zSection -> zSection.value.minOf { it.key } } }
     val yMax = blocks.maxOf { xSection -> xSection.value.maxOf { zSection -> zSection.value.maxOf { it.key } } }
     val clamp = FloatClamp(yMin, yMax)
 
-    return buildHeatMapImage(clamp) { x, z -> blocks[x]?.get(z)?.maxOf { it.key } }
+    return buildHeatMapImage(expanse, clamp) { x, z -> blocks[x]?.get(z)?.maxOf { it.key } }
   }
 
-  fun buildHeatMapImage(clamp: FloatClamp, calculate: (Long, Long) -> Long?): BufferedImage =
-    buildPixelQuadImage { x, z ->
+  fun buildHeatMapImage(expanse: BlockExpanse, clamp: FloatClamp, calculate: (Long, Long) -> Long?): BufferedImage =
+    buildPixelQuadImage(expanse) { x, z ->
       val value = calculate(x, z)
       val color = if (value != null) {
         val floatValue = clamp.convert(value)
@@ -65,13 +65,13 @@ class BlockStateImage {
     setRGB((x.toInt() * 2) + 1, (z.toInt() * 2) + 1, rgb)
   }
 
-  private fun buildPixelQuadImage(callback: BufferedImage.(Long, Long) -> Unit): BufferedImage {
-    val xMax = blocks.keys.maxOf { it }
-    val zMax = blocks.maxOf { xSection -> xSection.value.maxOf { zSection -> zSection.key } }
-    val bufferedImage = BufferedImage(xMax.toInt() * 2, zMax.toInt() * 2, BufferedImage.TYPE_4BYTE_ABGR)
+  private fun buildPixelQuadImage(expanse: BlockExpanse, callback: BufferedImage.(Long, Long) -> Unit): BufferedImage {
+    val width = expanse.size.x
+    val height = expanse.size.z
+    val bufferedImage = BufferedImage(width.toInt() * 2, height.toInt() * 2, BufferedImage.TYPE_4BYTE_ABGR)
 
-    for (x in 0 until xMax) {
-      for (z in 0 until zMax) {
+    for (x in 0 until width) {
+      for (z in 0 until height) {
         callback(bufferedImage, x, z)
       }
     }

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/render/BlockStateTracker.kt

@@ -1,4 +1,4 @@
-package cloud.kubelet.foundation.gjallarhorn
+package cloud.kubelet.foundation.gjallarhorn.render
 
 import kotlin.math.absoluteValue
 
@@ -17,7 +17,7 @@ class BlockStateTracker(private val mode: BlockTrackMode = BlockTrackMode.Remove
     }
   }
 
-  fun calculateZeroBlockOffset(): BlockOffset {
+  fun calculateZeroBlockOffset(): BlockPosition {
     val x = blocks.keys.minOf { it.x }
     val y = blocks.keys.minOf { it.y }
     val z = blocks.keys.minOf { it.z }
@@ -26,12 +26,21 @@ class BlockStateTracker(private val mode: BlockTrackMode = BlockTrackMode.Remove
     val yOffset = if (y < 0) y.absoluteValue else 0
     val zOffset = if (z < 0) z.absoluteValue else 0
 
-    return BlockOffset(xOffset, yOffset, zOffset)
+    return BlockPosition(xOffset, yOffset, zOffset)
   }
 
-  fun populate(image: BlockStateImage, offset: BlockOffset = BlockOffset.none) {
+  fun calculateMaxBlock(): BlockPosition {
+    val x = blocks.keys.maxOf { it.x }
+    val y = blocks.keys.maxOf { it.y }
+    val z = blocks.keys.maxOf { it.z }
+    return BlockPosition(x, y, z)
+  }
+
+  fun isEmpty() = blocks.isEmpty()
+
+  fun populateStateImage(image: BlockStateImage, offset: BlockPosition = BlockPosition.zero) {
     blocks.forEach { (position, state) ->
-      val realPosition = offset.apply(position)
+      val realPosition = offset.applyAsOffset(position)
       image.put(realPosition, state)
     }
   }

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/render/BlockTrackMode.kt

@@ -1,4 +1,4 @@
-package cloud.kubelet.foundation.gjallarhorn
+package cloud.kubelet.foundation.gjallarhorn.render
 
 enum class BlockTrackMode {
   RemoveOnDelete,

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/util/ImageTools.kt

@@ -0,0 +1,11 @@
+package cloud.kubelet.foundation.gjallarhorn.util
+
+import java.awt.image.BufferedImage
+import java.io.File
+import javax.imageio.ImageIO
+
+fun BufferedImage.savePngFile(path: String) {
+  if (!ImageIO.write(this, "png", File(path))) {
+    throw RuntimeException("Unable to write PNG.")
+  }
+}