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      1 /*
      2  * Copyright 2011 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkBitmap.h"
      9 #include "SkRect.h"
     10 #include "Test.h"
     11 
     12 static const char* boolStr(bool value) {
     13     return value ? "true" : "false";
     14 }
     15 
     16 // these are in the same order as the SkColorType enum
     17 static const char* gColorTypeName[] = {
     18     "None", "A8", "565", "4444", "RGBA", "BGRA", "Index8"
     19 };
     20 
     21 static void report_opaqueness(skiatest::Reporter* reporter, const SkBitmap& src,
     22                               const SkBitmap& dst) {
     23     ERRORF(reporter, "src %s opaque:%d, dst %s opaque:%d",
     24            gColorTypeName[src.colorType()], src.isOpaque(),
     25            gColorTypeName[dst.colorType()], dst.isOpaque());
     26 }
     27 
     28 static bool canHaveAlpha(SkColorType ct) {
     29     return kRGB_565_SkColorType != ct;
     30 }
     31 
     32 // copyTo() should preserve isOpaque when it makes sense
     33 static void test_isOpaque(skiatest::Reporter* reporter,
     34                           const SkBitmap& srcOpaque, const SkBitmap& srcPremul,
     35                           SkColorType dstColorType) {
     36     SkBitmap dst;
     37 
     38     if (canHaveAlpha(srcPremul.colorType()) && canHaveAlpha(dstColorType)) {
     39         REPORTER_ASSERT(reporter, srcPremul.copyTo(&dst, dstColorType));
     40         REPORTER_ASSERT(reporter, dst.colorType() == dstColorType);
     41         if (srcPremul.isOpaque() != dst.isOpaque()) {
     42             report_opaqueness(reporter, srcPremul, dst);
     43         }
     44     }
     45 
     46     REPORTER_ASSERT(reporter, srcOpaque.copyTo(&dst, dstColorType));
     47     REPORTER_ASSERT(reporter, dst.colorType() == dstColorType);
     48     if (srcOpaque.isOpaque() != dst.isOpaque()) {
     49         report_opaqueness(reporter, srcOpaque, dst);
     50     }
     51 }
     52 
     53 static void init_src(const SkBitmap& bitmap) {
     54     SkAutoLockPixels lock(bitmap);
     55     if (bitmap.getPixels()) {
     56         if (bitmap.getColorTable()) {
     57             sk_bzero(bitmap.getPixels(), bitmap.getSize());
     58         } else {
     59             bitmap.eraseColor(SK_ColorWHITE);
     60         }
     61     }
     62 }
     63 
     64 static SkColorTable* init_ctable(SkAlphaType alphaType) {
     65     static const SkColor colors[] = {
     66         SK_ColorBLACK, SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE, SK_ColorWHITE
     67     };
     68     return new SkColorTable(colors, SK_ARRAY_COUNT(colors), alphaType);
     69 }
     70 
     71 struct Pair {
     72     SkColorType fColorType;
     73     const char* fValid;
     74 };
     75 
     76 // Utility functions for copyPixelsTo()/copyPixelsFrom() tests.
     77 // getPixel()
     78 // setPixel()
     79 // getSkConfigName()
     80 // struct Coordinates
     81 // reportCopyVerification()
     82 // writeCoordPixels()
     83 
     84 // Utility function to read the value of a given pixel in bm. All
     85 // values converted to uint32_t for simplification of comparisons.
     86 static uint32_t getPixel(int x, int y, const SkBitmap& bm) {
     87     uint32_t val = 0;
     88     uint16_t val16;
     89     uint8_t val8;
     90     SkAutoLockPixels lock(bm);
     91     const void* rawAddr = bm.getAddr(x,y);
     92 
     93     switch (bm.bytesPerPixel()) {
     94         case 4:
     95             memcpy(&val, rawAddr, sizeof(uint32_t));
     96             break;
     97         case 2:
     98             memcpy(&val16, rawAddr, sizeof(uint16_t));
     99             val = val16;
    100             break;
    101         case 1:
    102             memcpy(&val8, rawAddr, sizeof(uint8_t));
    103             val = val8;
    104             break;
    105         default:
    106             break;
    107     }
    108     return val;
    109 }
    110 
    111 // Utility function to set value of any pixel in bm.
    112 // bm.getConfig() specifies what format 'val' must be
    113 // converted to, but at present uint32_t can handle all formats.
    114 static void setPixel(int x, int y, uint32_t val, SkBitmap& bm) {
    115     uint16_t val16;
    116     uint8_t val8;
    117     SkAutoLockPixels lock(bm);
    118     void* rawAddr = bm.getAddr(x,y);
    119 
    120     switch (bm.bytesPerPixel()) {
    121         case 4:
    122             memcpy(rawAddr, &val, sizeof(uint32_t));
    123             break;
    124         case 2:
    125             val16 = val & 0xFFFF;
    126             memcpy(rawAddr, &val16, sizeof(uint16_t));
    127             break;
    128         case 1:
    129             val8 = val & 0xFF;
    130             memcpy(rawAddr, &val8, sizeof(uint8_t));
    131             break;
    132         default:
    133             // Ignore.
    134             break;
    135     }
    136 }
    137 
    138 // Helper struct to contain pixel locations, while avoiding need for STL.
    139 struct Coordinates {
    140 
    141     const int length;
    142     SkIPoint* const data;
    143 
    144     explicit Coordinates(int _length): length(_length)
    145                                      , data(new SkIPoint[length]) { }
    146 
    147     ~Coordinates(){
    148         delete [] data;
    149     }
    150 
    151     SkIPoint* operator[](int i) const {
    152         // Use with care, no bounds checking.
    153         return data + i;
    154     }
    155 };
    156 
    157 // A function to verify that two bitmaps contain the same pixel values
    158 // at all coordinates indicated by coords. Simplifies verification of
    159 // copied bitmaps.
    160 static void reportCopyVerification(const SkBitmap& bm1, const SkBitmap& bm2,
    161                             Coordinates& coords,
    162                             const char* msg,
    163                             skiatest::Reporter* reporter){
    164     bool success = true;
    165 
    166     // Confirm all pixels in the list match.
    167     for (int i = 0; i < coords.length; ++i) {
    168         success = success &&
    169                   (getPixel(coords[i]->fX, coords[i]->fY, bm1) ==
    170                    getPixel(coords[i]->fX, coords[i]->fY, bm2));
    171     }
    172 
    173     if (!success) {
    174         ERRORF(reporter, "%s [colortype = %s]", msg,
    175                gColorTypeName[bm1.colorType()]);
    176     }
    177 }
    178 
    179 // Writes unique pixel values at locations specified by coords.
    180 static void writeCoordPixels(SkBitmap& bm, const Coordinates& coords) {
    181     for (int i = 0; i < coords.length; ++i)
    182         setPixel(coords[i]->fX, coords[i]->fY, i, bm);
    183 }
    184 
    185 static const Pair gPairs[] = {
    186     { kUnknown_SkColorType,     "000000"  },
    187     { kAlpha_8_SkColorType,     "010101"  },
    188     { kIndex_8_SkColorType,     "011111"  },
    189     { kRGB_565_SkColorType,     "010101"  },
    190     { kARGB_4444_SkColorType,   "010111"  },
    191     { kN32_SkColorType,         "010111"  },
    192 };
    193 
    194 static const int W = 20;
    195 static const int H = 33;
    196 
    197 static void setup_src_bitmaps(SkBitmap* srcOpaque, SkBitmap* srcPremul,
    198                               SkColorType ct) {
    199     SkColorTable* ctOpaque = NULL;
    200     SkColorTable* ctPremul = NULL;
    201     if (kIndex_8_SkColorType == ct) {
    202         ctOpaque = init_ctable(kOpaque_SkAlphaType);
    203         ctPremul = init_ctable(kPremul_SkAlphaType);
    204     }
    205 
    206     srcOpaque->allocPixels(SkImageInfo::Make(W, H, ct, kOpaque_SkAlphaType),
    207                            NULL, ctOpaque);
    208     srcPremul->allocPixels(SkImageInfo::Make(W, H, ct, kPremul_SkAlphaType),
    209                            NULL, ctPremul);
    210     SkSafeUnref(ctOpaque);
    211     SkSafeUnref(ctPremul);
    212     init_src(*srcOpaque);
    213     init_src(*srcPremul);
    214 }
    215 
    216 DEF_TEST(BitmapCopy_extractSubset, reporter) {
    217     for (size_t i = 0; i < SK_ARRAY_COUNT(gPairs); i++) {
    218         SkBitmap srcOpaque, srcPremul;
    219         setup_src_bitmaps(&srcOpaque, &srcPremul, gPairs[i].fColorType);
    220 
    221         SkBitmap bitmap(srcOpaque);
    222         SkBitmap subset;
    223         SkIRect r;
    224         // Extract a subset which has the same width as the original. This
    225         // catches a bug where we cloned the genID incorrectly.
    226         r.set(0, 1, W, 3);
    227         bitmap.setIsVolatile(true);
    228         // Relies on old behavior of extractSubset failing if colortype is unknown
    229         if (kUnknown_SkColorType != bitmap.colorType() && bitmap.extractSubset(&subset, r)) {
    230             REPORTER_ASSERT(reporter, subset.width() == W);
    231             REPORTER_ASSERT(reporter, subset.height() == 2);
    232             REPORTER_ASSERT(reporter, subset.alphaType() == bitmap.alphaType());
    233             REPORTER_ASSERT(reporter, subset.isVolatile() == true);
    234 
    235             // Test copying an extracted subset.
    236             for (size_t j = 0; j < SK_ARRAY_COUNT(gPairs); j++) {
    237                 SkBitmap copy;
    238                 bool success = subset.copyTo(&copy, gPairs[j].fColorType);
    239                 if (!success) {
    240                     // Skip checking that success matches fValid, which is redundant
    241                     // with the code below.
    242                     REPORTER_ASSERT(reporter, gPairs[i].fColorType != gPairs[j].fColorType);
    243                     continue;
    244                 }
    245 
    246                 // When performing a copy of an extracted subset, the gen id should
    247                 // change.
    248                 REPORTER_ASSERT(reporter, copy.getGenerationID() != subset.getGenerationID());
    249 
    250                 REPORTER_ASSERT(reporter, copy.width() == W);
    251                 REPORTER_ASSERT(reporter, copy.height() == 2);
    252 
    253                 if (gPairs[i].fColorType == gPairs[j].fColorType) {
    254                     SkAutoLockPixels alp0(subset);
    255                     SkAutoLockPixels alp1(copy);
    256                     // they should both have, or both not-have, a colortable
    257                     bool hasCT = subset.getColorTable() != NULL;
    258                     REPORTER_ASSERT(reporter, (copy.getColorTable() != NULL) == hasCT);
    259                 }
    260             }
    261         }
    262 
    263         bitmap = srcPremul;
    264         bitmap.setIsVolatile(false);
    265         if (bitmap.extractSubset(&subset, r)) {
    266             REPORTER_ASSERT(reporter, subset.alphaType() == bitmap.alphaType());
    267             REPORTER_ASSERT(reporter, subset.isVolatile() == false);
    268         }
    269     }
    270 }
    271 
    272 DEF_TEST(BitmapCopy, reporter) {
    273     static const bool isExtracted[] = {
    274         false, true
    275     };
    276 
    277     for (size_t i = 0; i < SK_ARRAY_COUNT(gPairs); i++) {
    278         SkBitmap srcOpaque, srcPremul;
    279         setup_src_bitmaps(&srcOpaque, &srcPremul, gPairs[i].fColorType);
    280 
    281         for (size_t j = 0; j < SK_ARRAY_COUNT(gPairs); j++) {
    282             SkBitmap dst;
    283 
    284             bool success = srcPremul.copyTo(&dst, gPairs[j].fColorType);
    285             bool expected = gPairs[i].fValid[j] != '0';
    286             if (success != expected) {
    287                 ERRORF(reporter, "SkBitmap::copyTo from %s to %s. expected %s "
    288                        "returned %s", gColorTypeName[i], gColorTypeName[j],
    289                        boolStr(expected), boolStr(success));
    290             }
    291 
    292             bool canSucceed = srcPremul.canCopyTo(gPairs[j].fColorType);
    293             if (success != canSucceed) {
    294                 ERRORF(reporter, "SkBitmap::copyTo from %s to %s. returned %s "
    295                        "canCopyTo %s", gColorTypeName[i], gColorTypeName[j],
    296                        boolStr(success), boolStr(canSucceed));
    297             }
    298 
    299             if (success) {
    300                 REPORTER_ASSERT(reporter, srcPremul.width() == dst.width());
    301                 REPORTER_ASSERT(reporter, srcPremul.height() == dst.height());
    302                 REPORTER_ASSERT(reporter, dst.colorType() == gPairs[j].fColorType);
    303                 test_isOpaque(reporter, srcOpaque, srcPremul, dst.colorType());
    304                 if (srcPremul.colorType() == dst.colorType()) {
    305                     SkAutoLockPixels srcLock(srcPremul);
    306                     SkAutoLockPixels dstLock(dst);
    307                     REPORTER_ASSERT(reporter, srcPremul.readyToDraw());
    308                     REPORTER_ASSERT(reporter, dst.readyToDraw());
    309                     const char* srcP = (const char*)srcPremul.getAddr(0, 0);
    310                     const char* dstP = (const char*)dst.getAddr(0, 0);
    311                     REPORTER_ASSERT(reporter, srcP != dstP);
    312                     REPORTER_ASSERT(reporter, !memcmp(srcP, dstP,
    313                                                       srcPremul.getSize()));
    314                     REPORTER_ASSERT(reporter, srcPremul.getGenerationID() == dst.getGenerationID());
    315                 } else {
    316                     REPORTER_ASSERT(reporter, srcPremul.getGenerationID() != dst.getGenerationID());
    317                 }
    318             } else {
    319                 // dst should be unchanged from its initial state
    320                 REPORTER_ASSERT(reporter, dst.colorType() == kUnknown_SkColorType);
    321                 REPORTER_ASSERT(reporter, dst.width() == 0);
    322                 REPORTER_ASSERT(reporter, dst.height() == 0);
    323             }
    324         } // for (size_t j = ...
    325 
    326         // Tests for getSafeSize(), getSafeSize64(), copyPixelsTo(),
    327         // copyPixelsFrom().
    328         //
    329         for (size_t copyCase = 0; copyCase < SK_ARRAY_COUNT(isExtracted);
    330              ++copyCase) {
    331             // Test copying to/from external buffer.
    332             // Note: the tests below have hard-coded values ---
    333             //       Please take care if modifying.
    334 
    335             // Tests for getSafeSize64().
    336             // Test with a very large configuration without pixel buffer
    337             // attached.
    338             SkBitmap tstSafeSize;
    339             tstSafeSize.setInfo(SkImageInfo::Make(100000000U, 100000000U,
    340                                                   gPairs[i].fColorType, kPremul_SkAlphaType));
    341             int64_t safeSize = tstSafeSize.computeSafeSize64();
    342             if (safeSize < 0) {
    343                 ERRORF(reporter, "getSafeSize64() negative: %s",
    344                        gColorTypeName[tstSafeSize.colorType()]);
    345             }
    346             bool sizeFail = false;
    347             // Compare against hand-computed values.
    348             switch (gPairs[i].fColorType) {
    349                 case kUnknown_SkColorType:
    350                     break;
    351 
    352                 case kAlpha_8_SkColorType:
    353                 case kIndex_8_SkColorType:
    354                     if (safeSize != 0x2386F26FC10000LL) {
    355                         sizeFail = true;
    356                     }
    357                     break;
    358 
    359                 case kRGB_565_SkColorType:
    360                 case kARGB_4444_SkColorType:
    361                     if (safeSize != 0x470DE4DF820000LL) {
    362                         sizeFail = true;
    363                     }
    364                     break;
    365 
    366                 case kN32_SkColorType:
    367                     if (safeSize != 0x8E1BC9BF040000LL) {
    368                         sizeFail = true;
    369                     }
    370                     break;
    371 
    372                 default:
    373                     break;
    374             }
    375             if (sizeFail) {
    376                 ERRORF(reporter, "computeSafeSize64() wrong size: %s",
    377                        gColorTypeName[tstSafeSize.colorType()]);
    378             }
    379 
    380             int subW = 2;
    381             int subH = 2;
    382 
    383             // Create bitmap to act as source for copies and subsets.
    384             SkBitmap src, subset;
    385             SkColorTable* ct = NULL;
    386             if (kIndex_8_SkColorType == src.colorType()) {
    387                 ct = init_ctable(kPremul_SkAlphaType);
    388             }
    389 
    390             if (isExtracted[copyCase]) { // A larger image to extract from.
    391                 src.allocPixels(SkImageInfo::Make(2 * subW + 1, subH,
    392                                                   gPairs[i].fColorType,
    393                                                   kPremul_SkAlphaType));
    394             } else { // Tests expect a 2x2 bitmap, so make smaller.
    395                 src.allocPixels(SkImageInfo::Make(subW, subH,
    396                                                   gPairs[i].fColorType,
    397                                                   kPremul_SkAlphaType));
    398             }
    399             SkSafeUnref(ct);
    400 
    401             // Either copy src or extract into 'subset', which is used
    402             // for subsequent calls to copyPixelsTo/From.
    403             bool srcReady = false;
    404             // Test relies on older behavior that extractSubset will fail on
    405             // kUnknown_SkColorType
    406             if (kUnknown_SkColorType != src.colorType() &&
    407                 isExtracted[copyCase]) {
    408                 // The extractedSubset() test case allows us to test copy-
    409                 // ing when src and dst mave possibly different strides.
    410                 SkIRect r;
    411                 r.set(1, 0, 1 + subW, subH); // 2x2 extracted bitmap
    412 
    413                 srcReady = src.extractSubset(&subset, r);
    414             } else {
    415                 srcReady = src.copyTo(&subset);
    416             }
    417 
    418             // Not all configurations will generate a valid 'subset'.
    419             if (srcReady) {
    420 
    421                 // Allocate our target buffer 'buf' for all copies.
    422                 // To simplify verifying correctness of copies attach
    423                 // buf to a SkBitmap, but copies are done using the
    424                 // raw buffer pointer.
    425                 const size_t bufSize = subH *
    426                     SkColorTypeMinRowBytes(src.colorType(), subW) * 2;
    427                 SkAutoMalloc autoBuf (bufSize);
    428                 uint8_t* buf = static_cast<uint8_t*>(autoBuf.get());
    429 
    430                 SkBitmap bufBm; // Attach buf to this bitmap.
    431                 bool successExpected;
    432 
    433                 // Set up values for each pixel being copied.
    434                 Coordinates coords(subW * subH);
    435                 for (int x = 0; x < subW; ++x)
    436                     for (int y = 0; y < subH; ++y)
    437                     {
    438                         int index = y * subW + x;
    439                         SkASSERT(index < coords.length);
    440                         coords[index]->fX = x;
    441                         coords[index]->fY = y;
    442                     }
    443 
    444                 writeCoordPixels(subset, coords);
    445 
    446                 // Test #1 ////////////////////////////////////////////
    447 
    448                 const SkImageInfo info = SkImageInfo::Make(subW, subH,
    449                                                            gPairs[i].fColorType,
    450                                                            kPremul_SkAlphaType);
    451                 // Before/after comparisons easier if we attach buf
    452                 // to an appropriately configured SkBitmap.
    453                 memset(buf, 0xFF, bufSize);
    454                 // Config with stride greater than src but that fits in buf.
    455                 bufBm.installPixels(info, buf, info.minRowBytes() * 2);
    456                 successExpected = false;
    457                 // Then attempt to copy with a stride that is too large
    458                 // to fit in the buffer.
    459                 REPORTER_ASSERT(reporter,
    460                     subset.copyPixelsTo(buf, bufSize, bufBm.rowBytes() * 3)
    461                     == successExpected);
    462 
    463                 if (successExpected)
    464                     reportCopyVerification(subset, bufBm, coords,
    465                         "copyPixelsTo(buf, bufSize, 1.5*maxRowBytes)",
    466                         reporter);
    467 
    468                 // Test #2 ////////////////////////////////////////////
    469                 // This test should always succeed, but in the case
    470                 // of extracted bitmaps only because we handle the
    471                 // issue of getSafeSize(). Without getSafeSize()
    472                 // buffer overrun/read would occur.
    473                 memset(buf, 0xFF, bufSize);
    474                 bufBm.installPixels(info, buf, subset.rowBytes());
    475                 successExpected = subset.getSafeSize() <= bufSize;
    476                 REPORTER_ASSERT(reporter,
    477                     subset.copyPixelsTo(buf, bufSize) ==
    478                         successExpected);
    479                 if (successExpected)
    480                     reportCopyVerification(subset, bufBm, coords,
    481                     "copyPixelsTo(buf, bufSize)", reporter);
    482 
    483                 // Test #3 ////////////////////////////////////////////
    484                 // Copy with different stride between src and dst.
    485                 memset(buf, 0xFF, bufSize);
    486                 bufBm.installPixels(info, buf, subset.rowBytes()+1);
    487                 successExpected = true; // Should always work.
    488                 REPORTER_ASSERT(reporter,
    489                         subset.copyPixelsTo(buf, bufSize,
    490                             subset.rowBytes()+1) == successExpected);
    491                 if (successExpected)
    492                     reportCopyVerification(subset, bufBm, coords,
    493                     "copyPixelsTo(buf, bufSize, rowBytes+1)", reporter);
    494 
    495                 // Test #4 ////////////////////////////////////////////
    496                 // Test copy with stride too small.
    497                 memset(buf, 0xFF, bufSize);
    498                 bufBm.installPixels(info, buf, info.minRowBytes());
    499                 successExpected = false;
    500                 // Request copy with stride too small.
    501                 REPORTER_ASSERT(reporter,
    502                     subset.copyPixelsTo(buf, bufSize, bufBm.rowBytes()-1)
    503                         == successExpected);
    504                 if (successExpected)
    505                     reportCopyVerification(subset, bufBm, coords,
    506                     "copyPixelsTo(buf, bufSize, rowBytes()-1)", reporter);
    507 
    508 #if 0   // copyPixelsFrom is gone
    509                 // Test #5 ////////////////////////////////////////////
    510                 // Tests the case where the source stride is too small
    511                 // for the source configuration.
    512                 memset(buf, 0xFF, bufSize);
    513                 bufBm.installPixels(info, buf, info.minRowBytes());
    514                 writeCoordPixels(bufBm, coords);
    515                 REPORTER_ASSERT(reporter,
    516                     subset.copyPixelsFrom(buf, bufSize, 1) == false);
    517 
    518                 // Test #6 ///////////////////////////////////////////
    519                 // Tests basic copy from an external buffer to the bitmap.
    520                 // If the bitmap is "extracted", this also tests the case
    521                 // where the source stride is different from the dest.
    522                 // stride.
    523                 // We've made the buffer large enough to always succeed.
    524                 bufBm.installPixels(info, buf, info.minRowBytes());
    525                 writeCoordPixels(bufBm, coords);
    526                 REPORTER_ASSERT(reporter,
    527                     subset.copyPixelsFrom(buf, bufSize, bufBm.rowBytes()) ==
    528                         true);
    529                 reportCopyVerification(bufBm, subset, coords,
    530                     "copyPixelsFrom(buf, bufSize)",
    531                     reporter);
    532 
    533                 // Test #7 ////////////////////////////////////////////
    534                 // Tests the case where the source buffer is too small
    535                 // for the transfer.
    536                 REPORTER_ASSERT(reporter,
    537                     subset.copyPixelsFrom(buf, 1, subset.rowBytes()) ==
    538                         false);
    539 
    540 #endif
    541             }
    542         } // for (size_t copyCase ...
    543     }
    544 }
    545 
    546 #include "SkColorPriv.h"
    547 #include "SkUtils.h"
    548 
    549 /**
    550  *  Construct 4x4 pixels where we can look at a color and determine where it should be in the grid.
    551  *  alpha = 0xFF, blue = 0x80, red = x, green = y
    552  */
    553 static void fill_4x4_pixels(SkPMColor colors[16]) {
    554     for (int y = 0; y < 4; ++y) {
    555         for (int x = 0; x < 4; ++x) {
    556             colors[y*4+x] = SkPackARGB32(0xFF, x, y, 0x80);
    557         }
    558     }
    559 }
    560 
    561 static bool check_4x4_pixel(SkPMColor color, unsigned x, unsigned y) {
    562     SkASSERT(x < 4 && y < 4);
    563     return  0xFF == SkGetPackedA32(color) &&
    564             x    == SkGetPackedR32(color) &&
    565             y    == SkGetPackedG32(color) &&
    566             0x80 == SkGetPackedB32(color);
    567 }
    568 
    569 /**
    570  *  Fill with all zeros, which will never match any value from fill_4x4_pixels
    571  */
    572 static void clear_4x4_pixels(SkPMColor colors[16]) {
    573     sk_memset32(colors, 0, 16);
    574 }
    575 
    576 // Much of readPixels is exercised by copyTo testing, since readPixels is the backend for that
    577 // method. Here we explicitly test subset copies.
    578 //
    579 DEF_TEST(BitmapReadPixels, reporter) {
    580     const int W = 4;
    581     const int H = 4;
    582     const size_t rowBytes = W * sizeof(SkPMColor);
    583     const SkImageInfo srcInfo = SkImageInfo::MakeN32Premul(W, H);
    584     SkPMColor srcPixels[16];
    585     fill_4x4_pixels(srcPixels);
    586     SkBitmap srcBM;
    587     srcBM.installPixels(srcInfo, srcPixels, rowBytes);
    588 
    589     SkImageInfo dstInfo = SkImageInfo::MakeN32Premul(W, H);
    590     SkPMColor dstPixels[16];
    591 
    592     const struct {
    593         bool     fExpectedSuccess;
    594         SkIPoint fRequestedSrcLoc;
    595         SkISize  fRequestedDstSize;
    596         // If fExpectedSuccess, check these, otherwise ignore
    597         SkIPoint fExpectedDstLoc;
    598         SkIRect  fExpectedSrcR;
    599     } gRec[] = {
    600         { true,  { 0, 0 }, { 4, 4 }, { 0, 0 }, { 0, 0, 4, 4 } },
    601         { true,  { 1, 1 }, { 2, 2 }, { 0, 0 }, { 1, 1, 3, 3 } },
    602         { true,  { 2, 2 }, { 4, 4 }, { 0, 0 }, { 2, 2, 4, 4 } },
    603         { true,  {-1,-1 }, { 2, 2 }, { 1, 1 }, { 0, 0, 1, 1 } },
    604         { false, {-1,-1 }, { 1, 1 }, { 0, 0 }, { 0, 0, 0, 0 } },
    605     };
    606 
    607     for (size_t i = 0; i < SK_ARRAY_COUNT(gRec); ++i) {
    608         clear_4x4_pixels(dstPixels);
    609 
    610         dstInfo.fWidth = gRec[i].fRequestedDstSize.width();
    611         dstInfo.fHeight = gRec[i].fRequestedDstSize.height();
    612         bool success = srcBM.readPixels(dstInfo, dstPixels, rowBytes,
    613                                         gRec[i].fRequestedSrcLoc.x(), gRec[i].fRequestedSrcLoc.y());
    614 
    615         REPORTER_ASSERT(reporter, gRec[i].fExpectedSuccess == success);
    616         if (success) {
    617             const SkIRect srcR = gRec[i].fExpectedSrcR;
    618             const int dstX = gRec[i].fExpectedDstLoc.x();
    619             const int dstY = gRec[i].fExpectedDstLoc.y();
    620             // Walk the dst pixels, and check if we got what we expected
    621             for (int y = 0; y < H; ++y) {
    622                 for (int x = 0; x < W; ++x) {
    623                     SkPMColor dstC = dstPixels[y*4+x];
    624                     // get into src coordinates
    625                     int sx = x - dstX + srcR.x();
    626                     int sy = y - dstY + srcR.y();
    627                     if (srcR.contains(sx, sy)) {
    628                         REPORTER_ASSERT(reporter, check_4x4_pixel(dstC, sx, sy));
    629                     } else {
    630                         REPORTER_ASSERT(reporter, 0 == dstC);
    631                     }
    632                 }
    633             }
    634         }
    635     }
    636 }
    637 
    638