Adding direct access to SkMipMap levels.

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 "SkBitmap.h"
 #include "SkMipMap.h"
 #include "SkRandom.h"
 #include "Test.h"
 
-static void make_bitmap(SkBitmap* bm, SkRandom& rand) {
-    // for now, Build needs a min size of 2, otherwise it will return nullptr.
-    // 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->allocN32Pixels(w, h);
+static void make_bitmap(SkBitmap* bm, int width, int height) {
+    bm->allocN32Pixels(width, height);
     bm->eraseColor(SK_ColorWHITE);
 }
 
 DEF_TEST(MipMap, reporter) {
     SkBitmap bm;
     SkRandom rand;
 
     for (int i = 0; i < 500; ++i) {
-        make_bitmap(&bm, rand);
+        // for now, Build needs a min size of 2, otherwise it will return nullptr.
+        // should fix that to support 1 X N, where N > 1 to return non-null.
+        int width = 2 + rand.nextU() % 1000;
+        int height = 2 + rand.nextU() % 1000;
+        make_bitmap(&bm, width, height);
         SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, nullptr));
 
+        // Add 1 because SkMipMap doesn't store the base mip level.
+        // It stores levels 1-x, not 0-x.
+        REPORTER_ASSERT(reporter, mm->countLevels() + 1 == SkMipMap::ComputeLevelCount(width,
+                                                                                       height));
+
         REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1, nullptr));
         REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1 * 2, nullptr));
 
         SkMipMap::Level prevLevel;
         sk_bzero(&prevLevel, sizeof(prevLevel));
 
         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.fPixmap.addr());
                 REPORTER_ASSERT(reporter, level.fPixmap.width() > 0);
                 REPORTER_ASSERT(reporter, level.fPixmap.height() > 0);
                 REPORTER_ASSERT(reporter, (int)level.fPixmap.rowBytes() >= level.fPixmap.width() * 4);
 
                 if (prevLevel.fPixmap.addr()) {
                     REPORTER_ASSERT(reporter, level.fPixmap.width() <= prevLevel.fPixmap.width());
                     REPORTER_ASSERT(reporter, level.fPixmap.height() <= prevLevel.fPixmap.height());
                 }
                 prevLevel = level;
             }
         }
     }
 }
+
+static void test_mipmap_generation(int width, int height, int expectedMipLevelCount,
+                                   skiatest::Reporter* reporter) {
+    SkBitmap bm;
+    bm.allocN32Pixels(width, height);
+    bm.eraseColor(SK_ColorWHITE);
+    SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, nullptr));
+
+    const int mipLevelCount = mm->countLevels();
+    REPORTER_ASSERT(reporter, mipLevelCount == expectedMipLevelCount);
+    for (int i = 0; i < mipLevelCount; ++i) {
+        SkMipMap::Level level;
+        mm->getLevel(i, &level);
+        // Make sure the mipmaps contain valid data and that the sizes are
+        // correct
+        REPORTER_ASSERT(reporter, level.fPixmap.addr());
+
+        // + 1 because SkMipMap does not include the base mipmap level.
+        int twoToTheMipLevel = 1 << (i + 1);
+        int currentWidth = width / twoToTheMipLevel;
+        int currentHeight = height / twoToTheMipLevel;
+        REPORTER_ASSERT(reporter, level.fPixmap.width() == currentWidth);
+        REPORTER_ASSERT(reporter, level.fPixmap.height() == currentHeight);
+    }
+}
+
+DEF_TEST(MipMap_DirectLevelAccess, reporter) {
+    // create mipmap with invalid size
+    {
+        // SkMipMap current requires the dimensions be greater than 2x2
+        SkBitmap bm;
+        bm.allocN32Pixels(1, 1);
+        bm.eraseColor(SK_ColorWHITE);
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, nullptr));
+
+        REPORTER_ASSERT(reporter, mm == nullptr);
+    }
+
+
+    // check small mipmap's count and levels
+    // There should be 5 mipmap levels generated:
+    // 16x16, 8x8, 4x4, 2x2, 1x1
+    test_mipmap_generation(32, 32, 5, reporter);
+
+    // check large mipmap's count and levels
+    // There should be 9 mipmap levels generated:
+    // 500x500, 250x250, 125x125, 62x62, 31x31, 15x15, 7x7, 3x3. 1x1
+    test_mipmap_generation(1000, 1000, 9, reporter);
+}
+
+DEF_TEST(MipMap_ComputeLevelCount, reporter) {
+    // Test mipmaps with negative sizes
+    int negativeWidthResult = SkMipMap::ComputeLevelCount(-100, 100);
+    REPORTER_ASSERT(reporter, negativeWidthResult == 0);
+
+    int negativeHeightResult = SkMipMap::ComputeLevelCount(100, -100);
+    REPORTER_ASSERT(reporter, negativeHeightResult == 0);
+
+    int negativeBothResult = SkMipMap::ComputeLevelCount(-100, -100);
+    REPORTER_ASSERT(reporter, negativeBothResult == 0);
+
+
+    // Test mipmaps with 0, 1, 2 as dimensions
+    // (SkMipMap::Build requires a min size of 2)
+    //
+    // 0
+    int zeroWidthResult = SkMipMap::ComputeLevelCount(0, 100);
+    REPORTER_ASSERT(reporter, zeroWidthResult == 0);
+
+    int zeroHeightResult = SkMipMap::ComputeLevelCount(100, 0);
+    REPORTER_ASSERT(reporter, zeroHeightResult == 0);
+
+    int zeroBothResult = SkMipMap::ComputeLevelCount(0, 0);
+    REPORTER_ASSERT(reporter, zeroBothResult == 0);
+
+    // 1
+    int oneWidthResult = SkMipMap::ComputeLevelCount(1, 100);
+    REPORTER_ASSERT(reporter, oneWidthResult == 0);
+
+    int oneHeightResult = SkMipMap::ComputeLevelCount(100, 1);
+    REPORTER_ASSERT(reporter, oneHeightResult == 0);
+
+    int oneBothResult = SkMipMap::ComputeLevelCount(1, 1);
+    REPORTER_ASSERT(reporter, oneBothResult == 0);
+
+    // 2
+    int twoWidthResult = SkMipMap::ComputeLevelCount(2, 100);
+    REPORTER_ASSERT(reporter, twoWidthResult == 2);
+
+    int twoHeightResult = SkMipMap::ComputeLevelCount(100, 2);
+    REPORTER_ASSERT(reporter, twoHeightResult == 2);
+
+    int twoBothResult = SkMipMap::ComputeLevelCount(2, 2);
+    REPORTER_ASSERT(reporter, twoBothResult == 2);
+
+
+    // Test a handful of boundaries such as 63x63 and 64x64
+    int sixtyThreeResult = SkMipMap::ComputeLevelCount(63, 63);
+    REPORTER_ASSERT(reporter, sixtyThreeResult == 6);
+
+    int sixtyFourResult = SkMipMap::ComputeLevelCount(64, 64);
+    REPORTER_ASSERT(reporter, sixtyFourResult == 7);
+
+    int oneHundredTwentySevenResult = SkMipMap::ComputeLevelCount(127, 127);
+    REPORTER_ASSERT(reporter, oneHundredTwentySevenResult == 7);
+
+    int oneHundredTwentyEightResult = SkMipMap::ComputeLevelCount(128, 128);
+    REPORTER_ASSERT(reporter, oneHundredTwentyEightResult == 8);
+
+    int twoHundredFiftyFiveResult = SkMipMap::ComputeLevelCount(255, 255);
+    REPORTER_ASSERT(reporter, twoHundredFiftyFiveResult == 8);
+
+    int twoHundredFiftySixResult = SkMipMap::ComputeLevelCount(256, 256);
+    REPORTER_ASSERT(reporter, twoHundredFiftySixResult == 9);
+
+
+    // Test different dimensions, such as 256x64
+    int smallestAxisIsSixtyFourResult = SkMipMap::ComputeLevelCount(64, 129);
+    REPORTER_ASSERT(reporter, smallestAxisIsSixtyFourResult == 7);
+
+    int smallestAxisIsThirtyTwoResult = SkMipMap::ComputeLevelCount(255, 32);
+    REPORTER_ASSERT(reporter, smallestAxisIsThirtyTwoResult == 6);
+
+    int smallestAxisIsFiveHundredResult = SkMipMap::ComputeLevelCount(500, 1000);
+    REPORTER_ASSERT(reporter, smallestAxisIsFiveHundredResult == 9);
+
+    // Test a few calls to SkMipMap::Build to make sure it matches
+    // SkMipMap::ComputeLevelCount
+    //
+    // Add 1 to mm->countLevels() because SkMipMap does not contain the base
+    // mipmap level.
+    // It contains mipmap levels 1-x, not 0-x.
+    {
+        SkBitmap bm;
+        bm.allocN32Pixels(255, 255);
+        bm.eraseColor(SK_ColorWHITE);
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, nullptr));
+
+        REPORTER_ASSERT(reporter, mm->countLevels() + 1 == SkMipMap::ComputeLevelCount(255, 255));
+    }
+
+    {
+        SkBitmap bm;
+        bm.allocN32Pixels(32, 32);
+        bm.eraseColor(SK_ColorWHITE);
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, nullptr));
+
+        REPORTER_ASSERT(reporter, mm->countLevels() + 1 == SkMipMap::ComputeLevelCount(32, 32));
+    }
+
+    {
+        SkBitmap bm;
+        bm.allocN32Pixels(1000, 1000);
+        bm.eraseColor(SK_ColorWHITE);
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(bm, nullptr));
+
+        REPORTER_ASSERT(reporter, mm->countLevels() + 1 == SkMipMap::ComputeLevelCount(1000, 1000));
+    }
+}