[orx-fx] Add DirectionalBlur

orx-fx/src/demo/kotlin/DemoDirectionalBlur01.kt

@@ -0,0 +1,38 @@
+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.draw.*
+import org.openrndr.extra.fx.blur.DirectionalBlur
+import org.openrndr.math.smoothstep
+import kotlin.math.cos
+import kotlin.math.sin
+
+fun main() = application {
+    program {
+        val db = DirectionalBlur()
+        val rt = renderTarget(width, height) {
+            colorBuffer()
+        }
+
+        val blurred = colorBuffer(width, height)
+        val direction = colorBuffer(width, height, type = ColorType.FLOAT32)
+        val s = direction.shadow
+        for (y in 0 until height) {
+            for (x in 0 until width) {
+                val a = smoothstep(0.45, 0.55, cos((x + y) * 0.01) * 0.5 + 0.5)
+                s[x, y] = ColorRGBa(cos(y * .1) * a, sin(x * 0.1) * a, 0.0, 1.0)
+            }
+        }
+
+        s.upload()
+        val image = loadImage("demo-data/images/image-001.png")
+        extend {
+            drawer.isolatedWithTarget(rt) {
+                clear(ColorRGBa.BLACK)
+                drawer.image(image)
+            }
+            db.window = 10
+            db.apply(arrayOf(rt.colorBuffer(0), direction), blurred)
+            drawer.image(blurred)
+        }
+    }
+}