add gm: colorwheel

gm/colorwheel.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Resources.h"
+#include "SkData.h"
+#include "SkDecodingImageGenerator.h"
+#include "gm.h"
+
+static void checkerboard(
+        SkCanvas* canvas, int w, int h, int size, SkColor c1, SkColor c2) {
+    SkAutoCanvasRestore autoCanvasRestore(canvas, true);
+    canvas->clipRect(SkRect::MakeWH(SkIntToScalar(w), SkIntToScalar(h)));
+    canvas->drawColor(c1);
+    SkPaint paint;
+    paint.setColor(c2);
+    SkScalar s = SkIntToScalar(size);
+    for (int y = 0; y < h; y += size) {
+        SkScalar ty = SkIntToScalar(y);
+        bool oddRow = (y % (2 * size)) != 0;
+        for (int x = oddRow ? size : 0; x < w; x += (2 * size)) {
+            SkScalar tx = SkIntToScalar(x);
+            canvas->drawRect(SkRect::MakeXYWH(tx, ty, s, s), paint);
+        }
+    }
+}
+
+static void draw_bitmap(SkCanvas* canvas, const char* resource, int x, int y) {
+    SkBitmap bitmap;
+    if (GetResourceAsBitmap(resource, &bitmap)) {
+        canvas->drawBitmap(bitmap, SkIntToScalar(x), SkIntToScalar(y));
+    } else {
+        SkDebugf("\nCould not decode file '%s'. Did you forget"
+                 " to set the resourcePath?\n", resource);
+    }
+}
+
+/*
+  This GM tests whether the image decoders properly decode each color
+  channel.  Four copies of the same image should appear in the GM, and
+  the letter R should be red, B should be blue, G green, C cyan, M
+  magenta, Y yellow, and K black. In all but the JPEG version of the
+  image, the letters should be on a white disc on a transparent
+  background (rendered as a checkerboard).  The JPEG image has a grey
+  background and compression artifacts.
+ */
+DEF_SIMPLE_GM(colorwheel, canvas, 256, 256) {
+    canvas->clear(SK_ColorWHITE);
+    checkerboard(canvas, 256, 556, 8, 0xFF999999, 0xFF666666);
+    draw_bitmap(canvas, "color_wheel.png", 0, 0);  // top left
+    draw_bitmap(canvas, "color_wheel.gif", 128, 0);  // top right
+    draw_bitmap(canvas, "color_wheel.webp", 0, 128);  // bottom left
+    draw_bitmap(canvas, "color_wheel.jpg", 128, 128);  // bottom right
+}