Add screenshot generation

build.gradle

@@ -16,7 +16,7 @@ buildscript {
 apply plugin: 'org.jetbrains.dokka'
 
 project.ext {
-    openrndrVersion = "0.3.41"
+    openrndrVersion = "0.4.0-SNAPSHOT"
     kotlinVersion = "1.3.72"
     spekVersion = "2.0.10"
     libfreenectVersion = "0.5.7-1.5.3"
@@ -62,6 +62,7 @@ allprojects {
     group 'org.openrndr.extra'
 
     repositories {
+        mavenLocal()
         mavenCentral()
         jcenter()
         maven {
@@ -124,4 +125,39 @@ allprojects {
             includeEngines 'spek2'
         }
     }
+
+
+}
+
+task collectScreenshots(dependsOn: 'classes') {
+    doFirst {
+        for (sub in project.subprojects) {
+            if (sub.sourceSets.hasProperty("demo")) {
+                def set = sub.sourceSets.demo
+                def ucl = new URLClassLoader(set.runtimeClasspath.collect { it.toURI().toURL() } as URL[])
+                for (x in set.output) {
+                    if (x.exists()) {
+                        for (y in x.listFiles()) {
+                            def name = y.name
+                            if (!name.contains('$') && name.contains(".class")) {
+                                def klass = ucl.loadClass(y.name.replace(".class", ""))
+                                try {
+                                    def mainMethod = klass.getMethod("main")
+                                    javaexec {
+                                        classpath set.runtimeClasspath
+                                        def className = y.name.replace(".class", "")
+                                        main = className
+                                        jvmArgs += "-DtakeScreenshot=true"
+                                        jvmArgs += "-DscreenshotPath=${sub.name}/images/${className}.png"
+                                    }
+                                } catch (e) {
+                                    // skip?
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
 }