Add drawToImage method in Background

src/com/annimon/turrets/Background.java

@@ -5,6 +5,7 @@ import static com.annimon.turrets.Constants.WIDTH;
 import com.annimon.turrets.util.Util;
 import java.awt.Color;
 import java.awt.Graphics;
+import java.awt.image.BufferedImage;
 
 /**
  *
@@ -12,12 +13,18 @@ import java.awt.Graphics;
  */
 public final class Background {
     
+    public static void drawToImage(BufferedImage img) {
+        final Graphics g = img.createGraphics();
+        new Background().draw(g);
+        g.dispose();
+    }
+    
     private static final int STARS_COUNT = (int) Math.sqrt(WIDTH * HEIGHT);
     
     private final Color bg, color;
     private final double shadeAmount;
 
-    public Background() {
+    private Background() {
         bg = new Color(Util.randomColor(0, 15));
         color = new Color(Util.randomColor(150, 235));
         shadeAmount = Util.rand(0.5, 2.5);

src/com/annimon/turrets/GameCanvas.java

@@ -11,7 +11,6 @@ import com.annimon.turrets.util.ExceptionHandler;
 import com.annimon.turrets.util.Util;
 import java.awt.Color;
 import java.awt.FontMetrics;
-import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
@@ -154,9 +153,7 @@ public final class GameCanvas extends DoubleBufferedCanvas implements Runnable,
     }
     
     private void initBackground() {
-        final Graphics g = background.createGraphics();
+        Background.drawToImage(background);
-        new Background().draw(g);
-        g.dispose();
     }
     
     private void startGame(long seed) {

src/com/annimon/turrets/util/GuiUtil.java

@@ -23,41 +23,45 @@ public final class GuiUtil {
         return new JLayer<>(component, (LayerUI<T>) new PlanetBackground());
     }
     
-    public static class GradientBackground extends javax.swing.plaf.LayerUI<JComponent> {
+    public static <T extends JComponent> JLayer<T> createGradientLayer(T component) {
+        return new JLayer<>(component, (LayerUI<T>) new GradientBackground());
+    }
+    
+    private static class GradientBackground extends BackgroundLayer {
 
         @Override
-        public void paint(Graphics g, JComponent component) {
+        protected void paint(Graphics2D g2d, int w, int h) {
-            super.paint(g, component);
-            final int w = component.getWidth();
-            final int h = component.getHeight();
-            
-            Graphics2D g2d = (Graphics2D) g.create();
-            g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.25f));
             g2d.setPaint(new GradientPaint(0, 0, Color.BLACK, 0, h, Color.GREEN));
             g2d.fillRect(0, 0, w, h);
-            g2d.dispose();
         }
     }
     
-    public static class PlanetBackground extends javax.swing.plaf.LayerUI<JComponent> {
+    private static class PlanetBackground extends BackgroundLayer {
         
         private final BufferedImage image;
         
         public PlanetBackground() {
             image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
-            Graphics g = image.createGraphics();
+            Background.drawToImage(image);
-            new Background().draw(g);
-            g.dispose();
         }
 
+        @Override
+        protected void paint(Graphics2D g2d, int w, int h) {
+            g2d.drawImage(image, 0, 0, null);
+        }
+    }
+    
+    private static abstract class BackgroundLayer extends LayerUI<JComponent> {
+
         @Override
         public void paint(Graphics g, JComponent component) {
             super.paint(g, component);
-            
             Graphics2D g2d = (Graphics2D) g.create();
             g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.25f));
-            g2d.drawImage(image, 0, 0, null);
+            paint(g2d, component.getWidth(), component.getHeight());
             g2d.dispose();
         }
+        
+        protected abstract void paint(Graphics2D g, int w, int h);
     }
 }