Render GIFs in color, add an animation of solution 2025-07 to the README

Author: rhaendel

2025-07_laboratories-animation.gif

@@ -4,6 +4,8 @@ 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)
+
 ## It's all about Learning
 
 I started this repository in december 2024 using the [Advent of Code Kotlin Template][template] delivered by JetBrains.

README.md

@@ -1,6 +1,8 @@
 package de.ronny_h.aoc.extensions.animation
 
 import de.ronny_h.aoc.extensions.asList
+import java.awt.Color
+import java.awt.Color.DARK_GRAY
 import java.io.File
 
 class AnimationRecorder {
@@ -10,7 +12,7 @@ class AnimationRecorder {
         frames.add(frame.asList())
     }
 
-    fun saveTo(fileName: String) = frames
-        .map(List<String>::createImage)
+    fun saveTo(fileName: String, colors: Map<Char, Color> = emptyMap(), background: Color = DARK_GRAY) = frames
+        .map { it.createImage(colors, background) }
         .writeToGifFile(File(fileName))
 }

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

@@ -1,5 +1,7 @@
 package de.ronny_h.aoc.extensions.animation
 
+import java.awt.Color
+import java.awt.Color.LIGHT_GRAY
 import java.awt.Font
 import java.awt.Font.MONOSPACED
 import java.awt.Font.PLAIN
@@ -16,22 +18,36 @@ import javax.imageio.metadata.IIOMetadataNode
 import javax.imageio.stream.FileImageOutputStream
 import javax.imageio.stream.ImageOutputStream
 
+val green = Color(0, 153, 0)
+val lightGreen = Color(0, 186, 13)
+val purpleBlue = Color(15, 15, 35)
+val lightGrey = Color(204, 204, 204)
+val gray = Color(70, 70, 70)
+val darkGrey = Color(16, 16, 26)
 
-private const val fontSize = 20
+private const val scale = 1
+private const val fontSize = scale * 20
 private const val drawStartX = 3
-private const val rowHeight = fontSize + 1
+private const val rowHeight = fontSize + scale
 private const val colWidth = 3 / 5.0 * fontSize
+private const val timeBetweenFramesMS = 250
 private val font = Font(MONOSPACED, PLAIN, fontSize)
 
-fun List<String>.createImage(): BufferedImage {
+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 - 13
+    val height = size * rowHeight - scale * 13
     val bufferedImage = BufferedImage(width, height, TYPE_INT_RGB)
     val graphics2D = bufferedImage.graphics as Graphics2D
     graphics2D.font = font
     graphics2D.setRenderingHint(KEY_TEXT_ANTIALIASING, VALUE_TEXT_ANTIALIAS_ON)
+    graphics2D.background = background
+    graphics2D.clearRect(0, 0, width, height)
     forEachIndexed { rowNo, row ->
-        graphics2D.drawString(row, drawStartX, rowNo * rowHeight)
+        row.forEachIndexed { colNo, char ->
+            graphics2D.color = gifColors.getValue(char)
+            graphics2D.drawString("$char", (drawStartX + colNo * colWidth).toInt(), rowNo * rowHeight)
+        }
     }
     return bufferedImage
 }
@@ -113,10 +129,13 @@ class GifSequenceWriter(
 
 fun List<BufferedImage>.writeToGifFile(file: File) {
     FileImageOutputStream(file).use { out ->
-        GifSequenceWriter(out, first().type, 200, true).use { gifWriter ->
+        GifSequenceWriter(out, first().type, timeBetweenFramesMS, true).use { gifWriter ->
             forEach { image ->
                 gifWriter.write(image)
             }
+            repeat(3) {
+                gifWriter.write(last())
+            }
         }
     }
 }

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

@@ -1,14 +1,32 @@
 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
 
 fun main() = Laboratories().run(1600, 8632253783011)
 
 class Laboratories : AdventOfCode<Long>(2025, 7) {
-    override fun part1(input: List<String>): Long = TachyonManifoldDiagram(input).followTheBeam().splitterCount
+    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",
+            mapOf(
+                emptySpace to gray,
+                splitter to lightGreen,
+                beam to white,
+            ),
+            purpleBlue,
+        )
+        return splitterCount
+    }
 
     override fun part2(input: List<String>): Long = TachyonManifoldDiagram(input).followTheBeam().numberOfTimeLines
 }

src/main/kotlin/de/ronny_h/aoc/year2025/day07/Laboratories.kt

@@ -3,6 +3,7 @@ package de.ronny_h.aoc.extensions.animation
 import io.kotest.core.spec.style.FunSpec
 import io.kotest.engine.spec.tempfile
 import io.kotest.matchers.shouldBe
+import java.awt.Color.BLACK
 import javax.imageio.ImageIO
 
 
@@ -13,8 +14,9 @@ class GifSequenceWriterTest : FunSpec({
     test("a GIF can be rendered from a list of Strings and be written to a file") {
         val frames = List(3) { i ->
             val text = buildList { repeat(5) { add("$i".repeat(5)) } }
-            text.createImage()
+            text.createImage(emptyMap(), BLACK)
         }
+//        frames.writeToGifFile(File("reference.gif"))
         frames.writeToGifFile(file)
 
         val newImage = ImageIO.read(file)