add trig

src/Prop.php

@@ -6,12 +6,20 @@ enum Prop
 {
     case LINEAR;
     case WAVE;
+    case TRIG;
 
+    /**
+     * Function for final color calculation.
+     * $i is the position of the line which is drawn in pixels. This can be between 0 and the image height.
+     * $height is the full height of the image.
+     * Return value should be between 0 and 1.
+     */
     public function calculatorCallback(): callable
     {
         return match ($this) {
             static::LINEAR => fn ($i, $height) => $i / $height,
             static::WAVE => fn ($i, $height) => abs(($i / $height) - 0.5),
+            static::TRIG => fn ($i, $height) => (cos(2 * pi() * $i / $height) + 1) / 2,
         };
     }
 }