One more animation: 2025-04 (Printing Department)

* Fix a bug in GifSequenceWriter: The first row was not visible.
* Add a new markdown file, dedicated to animations of grid-based solutions.
* Add an animation for year 2025, day 4, part 2.

Author: rhaendel

2025-07_laboratories-animation.gif

@@ -4,7 +4,9 @@ Welcome to the Advent of Code[^aoc] Kotlin project created by [rhaendel][github]
 
 In this repository, rhaendel is about to provide solutions for the puzzles using [Kotlin][kotlin] language.
 
-![Laboratories animation](2025-07_laboratories-animation.gif)
+![Laboratories animation](animations/2025-07_Laboratories.gif)
+
+*More animated GIFs can be found at [here](animations/animations.md).*
 
 ## It's all about Learning
 
@@ -48,16 +50,22 @@ If you're stuck with Kotlin-specific questions or anything related to this templ
 - [Kotlin Slack][slack]
 - Template [issue tracker][issues]
 
-
 [^aoc]:
-    [Advent of Code][aoc] – An annual event of Christmas-oriented programming challenges started December 2015.
-    Every year since then, beginning on the first day of December, a programming puzzle is published every day for twenty-five days.
-    You can solve the puzzle and provide an answer using the language of your choice.
+[Advent of Code][aoc] – An annual event of Christmas-oriented programming challenges started December 2015.
+Every year since then, beginning on the first day of December, a programming puzzle is published every day for
+twenty-five days.
+You can solve the puzzle and provide an answer using the language of your choice.
 
 [aoc]: https://adventofcode.com
+
 [docs]: https://kotlinlang.org/docs/home.html
+
 [github]: https://github.com/rhaendel
+
 [issues]: https://github.com/kotlin-hands-on/advent-of-code-kotlin-template/issues
+
 [kotlin]: https://kotlinlang.org
+
 [slack]: https://surveys.jetbrains.com/s3/kotlin-slack-sign-up
+
 [template]: https://github.com/kotlin-hands-on/advent-of-code-kotlin-template

README.md

@@ -0,0 +1,17 @@
+## Animations
+
+Some animated GIFs for Grid-based puzzles.
+
+### Year 2025, Day 7 - Laboratories, Part 1
+
+The animation shows a recursive algorithm calculating the path of a tachyon beam moving downwards, being split by
+different splitters until it exits the tachyon manifold at the bottom.
+
+![Laboratories animation](2025-07_Laboratories.gif)
+
+### Year 2025, Day 4 - Printing Department, Part 2
+
+Iteratively, all accessible rolls of paper (those with fewer than four rolls of paper in their eight adjacent positions)
+are removed by a forklift.
+
+![Printing Department animation](2025-04_PrintingDepartment.gif)

animations/2025-04_PrintingDepartment.gif

@@ -1,18 +1,22 @@
 package de.ronny_h.aoc.extensions.animation
 
 import de.ronny_h.aoc.extensions.asList
+import io.github.oshai.kotlinlogging.KotlinLogging
 import java.awt.Color
-import java.awt.Color.DARK_GRAY
 import java.io.File
 
 class AnimationRecorder {
     private val frames = mutableListOf<List<String>>()
+    private val logger = KotlinLogging.logger {}
 
     fun record(frame: String) {
         frames.add(frame.asList())
     }
 
-    fun saveTo(fileName: String, colors: Map<Char, Color> = emptyMap(), background: Color = DARK_GRAY) = frames
-        .map { it.createImage(colors, background) }
-        .writeToGifFile(File(fileName))
+    fun saveTo(fileName: String, colors: Map<Char, Color> = emptyMap(), background: Color = purpleBlue) {
+        frames
+            .map { it.createImage(colors, background) }
+            .writeToGifFile(File(fileName))
+        logger.info { "An animation was saved to: $fileName" }
+    }
 }

animations/2025-07_Laboratories.gif

@@ -27,16 +27,17 @@ val darkGrey = Color(16, 16, 26)
 
 private const val scale = 1
 private const val fontSize = scale * 20
-private const val drawStartX = 3
 private const val rowHeight = fontSize + scale
 private const val colWidth = 3 / 5.0 * fontSize
+private const val drawStartX = 3
+private const val drawStartY = rowHeight - 2
 private const val timeBetweenFramesMS = 250
 private val font = Font(MONOSPACED, PLAIN, fontSize)
 
 fun List<String>.createImage(colors: Map<Char, Color>, background: Color): BufferedImage {
     val gifColors = colors.withDefault { LIGHT_GRAY }
     val width = 2 * drawStartX + (this.first().length * colWidth).toInt()
-    val height = size * rowHeight - scale * 13
+    val height = drawStartY + size * rowHeight - scale * 13
     val bufferedImage = BufferedImage(width, height, TYPE_INT_RGB)
     val graphics2D = bufferedImage.graphics as Graphics2D
     graphics2D.font = font
@@ -46,7 +47,7 @@ fun List<String>.createImage(colors: Map<Char, Color>, background: Color): Buffe
     forEachIndexed { rowNo, row ->
         row.forEachIndexed { colNo, char ->
             graphics2D.color = gifColors.getValue(char)
-            graphics2D.drawString("$char", (drawStartX + colNo * colWidth).toInt(), rowNo * rowHeight)
+            graphics2D.drawString("$char", (drawStartX + colNo * colWidth).toInt(), drawStartY + rowNo * rowHeight)
         }
     }
     return bufferedImage

animations/animations.md

@@ -1,21 +1,38 @@
 package de.ronny_h.aoc.year2025.day04
 
 import de.ronny_h.aoc.AdventOfCode
+import de.ronny_h.aoc.extensions.animation.gray
 import de.ronny_h.aoc.extensions.grids.SimpleCharGrid
 import de.ronny_h.aoc.year2025.day04.PaperGrid.Companion.EMPTY
+import de.ronny_h.aoc.year2025.day04.PaperGrid.Companion.PAPER
+import java.awt.Color.white
 
 fun main() = PrintingDepartment().run(1397, 8758)
 
 class PrintingDepartment : AdventOfCode<Int>(2025, 4) {
     override fun part1(input: List<String>): Int = PaperGrid(input).accessiblePaperRollsCoordinates().count()
 
+    // find an animation at: /animations/2025-04_PrintingDepartment.gif
     override fun part2(input: List<String>): Int {
         val grid = PaperGrid(input)
+//        grid.recorder = AnimationRecorder()
+        val result = grid.removeAllAccessiblePaperRolls()
+        grid.recorder?.saveTo(
+            "animations/$year-${paddedDay()}_${javaClass.simpleName}.gif",
+            mapOf(
+                PAPER to white,
+                EMPTY to gray,
+            ),
+        )
+        return result
+    }
+
+    private fun PaperGrid.removeAllAccessiblePaperRolls(): Int {
         var total = 0
         while (true) {
-            grid.accessiblePaperRollsCoordinates().toList().apply {
+            accessiblePaperRollsCoordinates().toList().apply {
                 if (isEmpty()) return total
-                forEach { grid[it] = EMPTY }
+                forEach { set(it, EMPTY) }
                 total += size
             }
         }
@@ -25,7 +42,7 @@ class PrintingDepartment : AdventOfCode<Int>(2025, 4) {
 class PaperGrid(input: List<String>) : SimpleCharGrid(input, EMPTY) {
 
     companion object {
-        private const val PAPER = '@'
+        const val PAPER = '@'
         const val EMPTY = '.'
     }
 

src/main/kotlin/de/ronny_h/aoc/extensions/animation/AnimationRecorder.kt

@@ -3,27 +3,29 @@ package de.ronny_h.aoc.year2025.day07
 import de.ronny_h.aoc.AdventOfCode
 import de.ronny_h.aoc.extensions.animation.gray
 import de.ronny_h.aoc.extensions.animation.lightGreen
-import de.ronny_h.aoc.extensions.animation.purpleBlue
 import de.ronny_h.aoc.extensions.grids.Coordinates
 import de.ronny_h.aoc.extensions.grids.Direction.*
 import de.ronny_h.aoc.extensions.grids.SimpleCharGrid
 import java.awt.Color.white
+import java.awt.Color.yellow
 
 fun main() = Laboratories().run(1600, 8632253783011)
 
 class Laboratories : AdventOfCode<Long>(2025, 7) {
+
+    // find an animation at: /animations/2025-07_Laboratories.gif
     override fun part1(input: List<String>): Long {
         val diagram = TachyonManifoldDiagram(input)
 //        diagram.recorder = AnimationRecorder()
         val splitterCount = diagram.followTheBeam().splitterCount
         diagram.recorder?.saveTo(
-            "2025-07_laboratories-animation.gif",
+            "animations/$year-${paddedDay()}_${javaClass.simpleName}.gif",
             mapOf(
+                start to yellow,
                 emptySpace to gray,
                 splitter to lightGreen,
                 beam to white,
             ),
-            purpleBlue,
         )
         return splitterCount
     }
@@ -36,15 +38,16 @@ data class TachyonManifoldInfo(val splitterCount: Long, val numberOfTimeLines: L
         TachyonManifoldInfo(splitterCount + other.splitterCount, numberOfTimeLines + other.numberOfTimeLines)
 }
 
+private const val start = 'S'
 private const val emptySpace = '.'
 private const val splitter = '^'
 private const val beam = '|'
 private const val outOfMap = '#'
 
 class TachyonManifoldDiagram(input: List<String>) : SimpleCharGrid(input, outOfMap) {
-    private val start = find('S')
+    private val startLocation = find(start)
 
-    fun followTheBeam(): TachyonManifoldInfo = followTheBeam(start + SOUTH)
+    fun followTheBeam(): TachyonManifoldInfo = followTheBeam(startLocation + SOUTH)
 
     private val timelinesStartingAt = mutableMapOf<Coordinates, Long>()