Optimize Adjust Color

Co-Authored-By: iLauncherDev <93844852+iLauncherDev@users.noreply.github.com>

source/funkin/graphics/shaders/AdjustColorShader.hx

@@ -1,15 +1,88 @@
 package funkin.graphics.shaders;
 
 import flixel.addons.display.FlxRuntimeShader;
+import flixel.math.FlxAngle;
 
-@:nullSafety
+/**
+ * This shader is a recreation of Adobe Animate/Flash's "Adjust Color" filter.
+ * Originally written by Rozebud https://github.com/ThatRozebudDude
+ *
+ * Adapted from Andrey-Postelzhuks shader found here: https://forum.unity.com/threads/hue-saturation-brightness-contrast-shader.260649/
+ * Hue rotation stuff is from here: https://www.w3.org/TR/filter-effects/#feColorMatrixElement
+ */
 class AdjustColorShader extends FlxRuntimeShader
 {
+  /**
+   * The hue adjustment.
+   */
   public var hue(default, set):Float = 0;
+
+  function set_hue(val:Float):Float
+  {
+    hue = val;
+
+    hueMatrix = makeHueMatrix(val * FlxAngle.TO_RAD);
+
+    updateFinalMatrix();
+    return val;
+  }
+
+  /**
+   * The saturation adjustment.
+   */
   public var saturation(default, set):Float = 0;
+
+  function set_saturation(val:Float):Float
+  {
+    saturation = val;
+
+    if (val > 0) val *= 3;
+    val = 1 + (val / 100);
+
+    saturationMatrix = makeSaturationMatrix(val);
+
+    updateFinalMatrix();
+    return val;
+  }
+
+  /**
+   * The brightness adjustment.
+   */
   public var brightness(default, set):Float = 0;
+
+  function set_brightness(val:Float):Float
+  {
+    brightness = val;
+
+    this.setFloat('brightness', val / 255);
+    return val;
+  }
+
+  /**
+   * The contrast adjustment.
+   */
   public var contrast(default, set):Float = 0;
 
+  function set_contrast(val:Float):Float
+  {
+    var e:Float = 2.718281828459045;
+
+    contrast = val;
+
+    val = 1 + (val / 100);
+    if (val > 1.0)
+    {
+      val = (((0.00852259 * Math.pow(e, 4.76454 * (val - 1.0))) * 1.01) - 0.0086078159) * 10.0; // Just roll with it...
+      val += 1.0;
+    }
+
+    this.setFloat('contrast', val);
+    return val;
+  }
+
+  var hueMatrix:Array<Float>;
+  var saturationMatrix:Array<Float>;
+
   public function new()
   {
     super(Assets.getText(Paths.frag('adjustColor')));
@@ -19,39 +92,51 @@ class AdjustColorShader extends FlxRuntimeShader
     contrast = 0;
   }
 
-  function set_hue(value:Float):Float
+  function updateFinalMatrix():Void
   {
-    this.setFloat('hue', value);
-    this.hue = value;
+    if (hueMatrix != null)
+    {
+      this.setFloatArray('hueMatrix', hueMatrix);
+    }
 
-    return this.hue;
+    if (saturationMatrix != null)
+    {
+      this.setFloatArray('saturationMatrix', saturationMatrix);
+    }
   }
 
-  function set_saturation(value:Float):Float
+  function makeHueMatrix(h:Float):Array<Float>
   {
-    this.setFloat('saturation', value);
-    this.saturation = value;
+    var c = Math.cos(h);
+    var s = Math.sin(h);
 
-    return this.saturation;
+    var wR = 0.299;
+    var wG = 0.587;
+    var wB = 0.114;
+
+    return [
+      wR + (1 - wR) * c - wR * s,          wG - wG * c - wG * s, wB - wB * c + (1 - wB) * s,
+         wR - wR * c + 0.143 * s, wG + (1 - wG) * c + 0.140 * s,    wB - wB * c - 0.283 * s,
+      wR - wR * c - (1 - wR) * s,          wG - wG * c + wG * s, wB + (1 - wB) * c + wB * s
+    ];
   }
 
-  function set_brightness(value:Float):Float
+  function makeSaturationMatrix(s:Float):Array<Float>
   {
-    this.setFloat('brightness', value);
-    this.brightness = value;
+    var lr = 0.2126;
+    var lg = 0.7152;
+    var lb = 0.0722;
 
-    return this.brightness;
+    var inv = 1.0 - s;
+
+    return [
+      lr * inv + s,     lg * inv,   lb * inv,
+          lr * inv, lg * inv + s,   lb * inv,
+          lr * inv,     lg * inv, lb * inv + s
+    ];
   }
 
-  function set_contrast(value:Float):Float
-  {
-    this.setFloat('contrast', value);
-    this.contrast = value;
-
-    return this.contrast;
-  }
-
-  override public function toString():String
+  public override function toString():String
   {
     return 'AdjustColorShader(${this.hue}, ${this.saturation}, ${this.brightness}, ${this.contrast})';
   }