Merge pull request #25 from theolundqvist/master

add 'updated' method to Image

src/main/scala/introprog/Image.scala

@@ -25,6 +25,13 @@ class Image (val underlying: java.awt.image.BufferedImage):
     for x <- 0 until width; y <- 0 until height do
         update(x, y, f(x, y))
 
+  /** Set color of pixels by passing `f(x, y)` and return self*/
+  def updated(f: (Int, Int) => Color): Image =
+    for x <- 0 until width; y <- 0 until height do
+        update(x, y, f(x, y))
+    this
+
+
   /** Extract and return image pixels.*/
   def toMatrix: Array[Array[Color]] = 
     val xs: Array[Array[Color]] = Array.ofDim(width, height)