From ccae5511ecab15475cea250f8bd4bc5f75d8397b Mon Sep 17 00:00:00 2001
From: Gregor Kleen <gkleen@yggdrasil.li>
Date: Tue, 17 Nov 2015 10:07:41 +0100
Subject: "Solution" for eip 04 - H4-2

---
 ws2015/eip/blaetter/04/Schleife.java | 43 +++++++++++++++++++++++++++++-------
 1 file changed, 35 insertions(+), 8 deletions(-)

(limited to 'ws2015')

diff --git a/ws2015/eip/blaetter/04/Schleife.java b/ws2015/eip/blaetter/04/Schleife.java
index 05e791b..a693cb0 100644
--- a/ws2015/eip/blaetter/04/Schleife.java
+++ b/ws2015/eip/blaetter/04/Schleife.java
@@ -1,20 +1,47 @@
 import java.awt.Rectangle;
+import java.awt.Color;
+import java.awt.Point;
 
 public class Schleife {
 
     public static void main(String[] args) {
-        int margin     = 25;
-        int box_height = 50;
-        int box_width  = 150;
-        Rectangle r1 = new Rectangle(margin, margin + box_width, box_width, box_height);
         GraphicsWindow gw = new GraphicsWindow();
-        gw.fill(r1);
 
-        // ... TODO ...
-
-        gw.setText("Klicken Sie zum Beenden.");
+        drawGradient(gw);
+        
         gw.mouseClick();
         System.exit(0);
     }
 
+    private static void drawGradient(GraphicsWindow gw) {
+        Color fg = gw.getColor();
+        for (Point p = new Point(0,0); p.y <= 480; p.move(0, p.y + 1)) // gw.GetWidth would have been nice
+            {
+                for (;p.x <= 640; p.move(p.x + 1, p.y))
+                         {
+                             gw.setColor(f(p.x, p.y) <= 0 ? Color.red : color(p.x, p.y));
+                             // System.out.format("%s in %s\n", p.toString(), gw.getColor().toString()); // DEBUG
+                             gw.drawPoint(p);
+                         }
+            }
+        gw.setColor(fg);
+    }
+
+    private static double f(int x, int y) {
+        double xprime = (x - 200) / 120;
+        double yprime = (200 - y) / 100;
+        return Math.pow(xprime * xprime + yprime * yprime - 1, 3) - (xprime * xprime * yprime * yprime * yprime);
+          // pow is comparatively expensive (at least it would be if this were C ;) )
+    }
+
+    private static Color color(int x, int y) {
+        // System.out.format("(%d, %d)\n", x, y); // DEBUG
+        double g = 0.15 * (1200 - x - y);
+        double b = 0.15 * (x + y);
+        return new Color((int) 0, (int) g, (int) b);
+        /* Why can’t we have nice things? Like proper type signatures?
+         * We introduce some error by truncating to integer -- We deemed this to be of no moment.
+         */
+    }
+
 }
-- 
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