Add string art GM and sample.

gm/stringart.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkCanvas.h"
+#include "SkPath.h"
+
+// Based on http://www.saccade.com/rtor/
+

[robertphillips, 2013/09/12 15:19:56]

Does it need to be this big?

[jvanverth1, 2013/09/12 16:55:44]

Done.

+static const int kWidth = 1909;
+static const int kHeight = 1105;
+static const SkScalar kAngle = 0.305f;
+

[robertphillips, 2013/09/12 15:19:56]

// description?

[jvanverth1, 2013/09/12 16:55:44]

Done.

+class StringArtGM : public skiagm::GM {
+public:
+    StringArtGM() {}
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("stringart");
+    }
+
+    virtual SkISize onISize() {
+        return SkISize::Make(kWidth, kHeight);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {

[robertphillips, 2013/09/12 15:19:56]

There is also SkScalarHalf()

[jvanverth1, 2013/09/12 16:55:44]

Done.

+        SkScalar angle = kAngle * SK_ScalarPI + SK_ScalarPI*SK_ScalarHalf;
+        SkScalar size = SkMin32( kWidth, kHeight );
+        SkPoint center = SkPoint::Make( kWidth*SK_ScalarHalf, kHeight*SK_ScalarHalf );
+        SkScalar length = 5;
+        SkScalar step = angle;
+
+        SkPath path;
+        path.moveTo(center);
+
+        while (length < (size*SK_ScalarHalf - 10.f))
+        {
+            SkPoint rp = SkPoint::Make(length * SkScalarCos(step) + center.fX,
+                                       length * SkScalarSin(step) + center.fY);
+            path.lineTo(rp);
+            length += angle/(SK_ScalarPI*SK_ScalarHalf);
+            step += angle;
+        }
+        path.close();
+
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setStyle(SkPaint::kStroke_Style);
+        paint.setColor(0xFF007700);
+
+        canvas->drawPath(path, paint);
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+DEF_GM( return new StringArtGM; )