Adds particle systems to sprites

sky/sdk/example/game/lib/color_secuence.dart

Index: sky/sdk/example/game/lib/color_secuence.dart
diff --git a/sky/sdk/example/game/lib/color_secuence.dart b/sky/sdk/example/game/lib/color_secuence.dart
new file mode 100644
index 0000000000000000000000000000000000000000..72e9a4000a185a342885ddef16d457e891e146e5
--- /dev/null
+++ b/sky/sdk/example/game/lib/color_secuence.dart
@@ -0,0 +1,88 @@
+part of sprites;
+
+class ColorSequence {
+  List<Color> colors;
+  List<double> colorStops;
+
+  ColorSequence(this.colors, this.colorStops) {
+    assert(colors != null);
+    assert(colorStops != null);
+    assert(colors.length == colorStops.length);
+  }
+
+  ColorSequence.fromStartAndEndColor(Color start, Color end) {
+    colors = [start, end];
+    colorStops = [0.0, 1.0];
+  }
+
+  ColorSequence.copy(ColorSequence sequence) {
+    colors = new List<Color>.from(sequence.colors);
+    colorStops = new List<double>.from(sequence.colorStops);
+  }
+
+  ColorSequence.copyWithVariance(ColorSequence sequence, int alphaVar, int redVar, int greenVar, int blueVar) {
+    colors = new List<Color>();
+    colorStops = new List<double>.from(sequence.colorStops);
+
+    Math.Random rand = new Math.Random();
+
+    for (Color color in sequence.colors) {
+      int aDelta = ((rand.nextDouble() * 2.0 - 1.0) * alphaVar).toInt();
+      int rDelta = ((rand.nextDouble() * 2.0 - 1.0) * redVar).toInt();
+      int gDelta = ((rand.nextDouble() * 2.0 - 1.0) * greenVar).toInt();
+      int bDelta = ((rand.nextDouble() * 2.0 - 1.0) * blueVar).toInt();
+
+      int aNew = _clamp(color.alpha + aDelta, 0, 255);
+      int rNew = _clamp(color.red + rDelta, 0, 255);
+      int gNew = _clamp(color.green + gDelta, 0, 255);
+      int bNew = _clamp(color.blue + bDelta, 0, 255);
+
+      colors.add(new Color.fromARGB(aNew, rNew, gNew, bNew));
+    }
+  }
+
+  int _clamp(int val, int min, int max) {
+    if (val < min) return min;
+    if (val > max) return max;
+    return val;
+  }
+
+  Color colorAtPosition(double pos) {
+    assert(pos >= 0.0 && pos <= 1.0);
+
+    double lastStop = colorStops[0];
+    Color lastColor = colors[0];
+
+    for (int i = 0; i < colors.length; i++) {
+      double currentStop = colorStops[i];
+      Color currentColor = colors[i];
+
+      if (pos <= currentStop) {
+        double blend = (pos - lastStop) / (currentStop - lastStop);
+        return _interpolateColor(lastColor, currentColor, blend);
+      }
+      lastStop = currentStop;
+      lastColor = currentColor;
+    }
+    return colors[colors.length-1];
+  }
+}
+
+Color _interpolateColor(Color a, Color b, double blend) {
+  double aa = a.alpha.toDouble();
+  double ar = a.red.toDouble();
+  double ag = a.green.toDouble();
+  double ab = a.blue.toDouble();
+
+  double ba = b.alpha.toDouble();
+  double br = b.red.toDouble();
+  double bg = b.green.toDouble();
+  double bb = b.blue.toDouble();
+
+  int na = (aa * (1.0 - blend) + ba * blend).toInt();
+  int nr = (ar * (1.0 - blend) + br * blend).toInt();
+  int ng = (ag * (1.0 - blend) + bg * blend).toInt();
+  int nb = (ab * (1.0 - blend) + bb * blend).toInt();
+
+  return new Color.fromARGB(na, nr, ng, nb);
+}