pull mipmap class into its own (private) header

tests/MipMapTest.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 "Test.h"
+#include "SkMipMap.h"
+#include "SkBitmap.h"
+#include "SkRandom.h"
+
+static void make_bitmap(SkBitmap* bm, SkRandom& rand) {
+    // for now, Build needs a min size of 2, otherwise it will return NULL.
+    // should fix that to support 1 X N, where N > 1 to return non-null.
+    int w = 2 + rand.nextU() % 1000;
+    int h = 2 + rand.nextU() % 1000;
+    bm->setConfig(SkBitmap::kARGB_8888_Config, w, h);
+    bm->allocPixels();
+    bm->eraseColor(SK_ColorWHITE);
+}
+
+static void TestMipMap(skiatest::Reporter* reporter) {
+    SkBitmap bm;
+    SkRandom rand;
+
+    for (int i = 0; i < 500; ++i) {
+        make_bitmap(&bm, rand);
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm));
+        
+        REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1, NULL));
+        REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1 * 2, NULL));
+        
+        SkMipMap::Level prevLevel;
+        prevLevel.fPixels = NULL;   // sentinel
+
+        SkScalar scale = SK_Scalar1;
+        for (int j = 0; j < 30; ++j) {
+            scale = scale * 2 / 3;
+
+            SkMipMap::Level level;
+            if (mm->extractLevel(scale, &level)) {
+                REPORTER_ASSERT(reporter, level.fPixels);
+                REPORTER_ASSERT(reporter, level.fWidth > 0);
+                REPORTER_ASSERT(reporter, level.fHeight > 0);
+                REPORTER_ASSERT(reporter, level.fRowBytes >= level.fWidth * 4);
+                
+                if (prevLevel.fPixels) {
+                    REPORTER_ASSERT(reporter, level.fWidth <= prevLevel.fWidth);
+                    REPORTER_ASSERT(reporter, level.fHeight <= prevLevel.fHeight);
+                }
+                prevLevel = level;
+            }
+        }
+    }
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("MipMap", MipMapTestClass, TestMipMap)