gm to illustrate mipmap layer choice

gm/mipmap.cpp

+/*
+ * Copyright 2015 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 "SkImage.h"
+#include "SkRandom.h"
+#include "SkSurface.h"
+
+static SkImage* make_image() {
+    const SkImageInfo info = SkImageInfo::MakeN32Premul(319, 52);
+    SkAutoTUnref<SkSurface> surface(SkSurface::NewRaster(info));
+    SkCanvas* canvas = surface->getCanvas();
+    canvas->drawColor(0xFFF8F8F8);
+
+    SkPaint paint;
+    paint.setAntiAlias(true);
+
+    paint.setStyle(SkPaint::kStroke_Style);
+    for (int i = 0; i < 20; ++i) {
+        canvas->drawCircle(-4, 25, 20, paint);
+        canvas->translate(25, 0);
+    }
+    return surface->newImageSnapshot();
+}
+
+static void test_mip(SkCanvas* canvas) {
+    SkAutoTUnref<SkImage> img(make_image());//SkImage::NewFromData(data));
+
+    SkPaint paint;
+    const SkRect dst = SkRect::MakeWH(177, 15);
+
+    paint.setTextSize(30);
+    SkString str;
+    str.printf("scale %g %g", dst.width() / img->width(), dst.height() / img->height());
+//    canvas->drawText(str.c_str(), str.size(), 300, 100, paint);
+
+    canvas->translate(20, 20);
+    for (int i = 0; i < 4; ++i) {
+        paint.setFilterLevel(SkPaint::FilterLevel(i));
+        canvas->drawImageRect(img, NULL, dst, &paint);
+        canvas->translate(0, 20);
+    }
+    canvas->drawImage(img, 20, 20, NULL);
+}
+
+class MipMapGM : public skiagm::GM {
+public:
+    MipMapGM() {}
+
+protected:
+    SkString onShortName() SK_OVERRIDE { return SkString("mipmap"); }
+
+    SkISize onISize() SK_OVERRIDE { return SkISize::Make(400, 200); }
+
+    void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        test_mip(canvas);
+    }
+
+private:
+    typedef skiagm::GM INHERITED;
+};
+DEF_GM( return new MipMapGM; )
+