Add screenshot generation

orx-fx/src/demo/kotlin/DemoFluidDistort01.kt

@@ -0,0 +1,30 @@
+import org.openrndr.application
+import org.openrndr.draw.colorBuffer
+import org.openrndr.extensions.SingleScreenshot
+import org.openrndr.extra.fx.distort.FluidDistort
+import org.openrndr.extra.fx.patterns.Checkers
+
+fun main() {
+    application {
+        program {
+            val fd = FluidDistort()
+            val checkers =  Checkers()
+
+            val image = colorBuffer(width, height)
+            val distorted = image.createEquivalent()
+            checkers.size = 64.0
+            checkers.apply(emptyArray(), image)
+
+            if (System.getProperty("takeScreenshot") == "true") {
+                extend(SingleScreenshot()) {
+                    this.outputFile = System.getProperty("screenshotPath")
+                }
+            }
+            extend {
+                fd.blend = mouse.position.x/width
+                fd.apply(image, distorted)
+                drawer.image(distorted)
+            }
+        }
+    }
+}