[orx-color] Add classic palette generators

orx-color/src/commonMain/kotlin/palettes/Classics.kt

@@ -0,0 +1,59 @@
+package org.openrndr.extra.color.palettes
+
+import org.openrndr.color.ColorModel
+import org.openrndr.color.ColorRGBa
+import org.openrndr.color.HueShiftableColor
+import org.openrndr.extra.color.tools.shiftHue
+
+/**
+ * Generate an analogous palette
+ * @param T the color model to use
+ */
+inline fun <reified T> ColorRGBa.analogous(hueShift: Double, steps: Int = 5): List<ColorRGBa>
+        where T : HueShiftableColor<T>,
+              T : ColorModel<T> = (0 until steps).map {
+    shiftHue<T>(hueShift * it / (steps - 1.0))
+}
+
+/**
+ * Generate a split complementary palette in which the receiver is the seed color
+ * @param T the color model to use
+ * @param splitFactor a value between 0 and 1 that indicates how much the complementary color should be split
+ * @param double should a double complementary palette be generated
+ */
+inline fun <reified T> ColorRGBa.splitComplementary(splitFactor: Double, double: Boolean = false): List<ColorRGBa>
+        where T : HueShiftableColor<T>,
+              T : ColorModel<T> {
+    val c0 = shiftHue<T>(180 - 180.0 * splitFactor)
+    val c1 = shiftHue<T>(180 + 180.0 * splitFactor)
+
+    if (!double) {
+        return listOf(this, c0, c1)
+    } else {
+        val c2 = shiftHue<T>(180.0 * splitFactor)
+        val c3 = shiftHue<T>(-180.0 * splitFactor)
+        return listOf(this, c0, c1, c2, c3)
+    }
+}
+
+/**
+ * Generate a triadic palette in which the receiver is the seed color.
+ * @param T the color model to use
+ */
+inline fun <reified T> ColorRGBa.triadic(): List<ColorRGBa>
+        where T : HueShiftableColor<T>,
+              T : ColorModel<T> = splitComplementary<T>(1.0 / 3.0)
+
+
+/**
+ * Generate a tetradic palette in which the receiver is the seed color.
+ * @param T the color model to use
+ * @param aspectRatio the aspect ratio between even and odd sides
+ */
+inline fun <reified T> ColorRGBa.tetradic(aspectRatio: Double = 1.0): List<ColorRGBa>
+        where T : HueShiftableColor<T>,
+              T : ColorModel<T> {
+    val a0 = 180 / (aspectRatio + 1)
+    val a1 = 180 - a0
+    return listOf(this, shiftHue<T>(a0), shiftHue<T>(a0 + a1), shiftHue<T>(a0 + a1 + a0))
+}