C++ SkImageInfo::computeMinByteSize方法代码示例

void draw(SkCanvas* canvas) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(2, 2);
    const size_t size = info.computeMinByteSize();
    SkAutoTMalloc<SkPMColor> storage(size);
    SkPMColor* pixels = storage.get();
    SkBitmap bitmap;
    bitmap.setInfo(info);
    bitmap.setPixels(pixels);
    bitmap.eraseColor(SK_ColorRED);
    canvas->scale(50, 50);
    canvas->rotate(8);
    canvas->drawBitmap(bitmap, 2, 0);
}

void draw(SkCanvas* ) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(3, 3);
    const size_t size = info.computeMinByteSize();
    SkAutoTMalloc<SkPMColor> storage(size);
    SkPMColor* pixels = storage.get();
    sk_sp<SkSurface> surface(SkSurface::MakeRasterDirect(info, pixels, info.minRowBytes()));
    SkCanvas* canvas = surface->getCanvas();
    canvas->clear(SK_ColorWHITE);
    SkPMColor pmWhite = pixels[0];
    SkPaint paint;
    canvas->drawPoint(1, 1, paint);
    canvas->flush();  // ensure that point was drawn
    for (int y = 0; y < info.height(); ++y) {
        for (int x = 0; x < info.width(); ++x) {
            SkDebugf("%c", *pixels++ == pmWhite ? '-' : 'x');
        }
        SkDebugf("\n");
    }
}

//.........这里部分代码省略.........
        // Save the vital fields
        directoryEntries[i].offset = offset;
        directoryEntries[i].size = size;
    }

    // Default Result, if no valid embedded codecs are found.
    *result = kInvalidInput;

    // It is "customary" that the embedded images will be stored in order of
    // increasing offset.  However, the specification does not indicate that
    // they must be stored in this order, so we will not trust that this is the
    // case.  Here we sort the embedded images by increasing offset.
    struct EntryLessThan {
        bool operator() (Entry a, Entry b) const {
            return a.offset < b.offset;
        }
    };
    EntryLessThan lessThan;
    SkTQSort(directoryEntries, &directoryEntries[numImages - 1], lessThan);

    // Now will construct a candidate codec for each of the embedded images
    uint32_t bytesRead = kIcoDirectoryBytes + numImages * kIcoDirEntryBytes;
    std::unique_ptr<SkTArray<std::unique_ptr<SkCodec>, true>> codecs(
            new SkTArray<std::unique_ptr<SkCodec>, true>(numImages));
    for (uint32_t i = 0; i < numImages; i++) {
        uint32_t offset = directoryEntries[i].offset;
        uint32_t size = directoryEntries[i].size;

        // Ensure that the offset is valid
        if (offset < bytesRead) {
            SkCodecPrintf("Warning: invalid ico offset.\n");
            continue;
        }

        // If we cannot skip, assume we have reached the end of the stream and
        // stop trying to make codecs
        if (stream->skip(offset - bytesRead) != offset - bytesRead) {
            SkCodecPrintf("Warning: could not skip to ico offset.\n");
            break;
        }
        bytesRead = offset;

        // Create a new stream for the embedded codec
        SkAutoFree buffer(sk_malloc_canfail(size));
        if (!buffer) {
            SkCodecPrintf("Warning: OOM trying to create embedded stream.\n");
            break;
        }

        if (stream->read(buffer.get(), size) != size) {
            SkCodecPrintf("Warning: could not create embedded stream.\n");
            *result = kIncompleteInput;
            break;
        }

        sk_sp<SkData> data(SkData::MakeFromMalloc(buffer.release(), size));
        auto embeddedStream = SkMemoryStream::Make(data);
        bytesRead += size;

        // Check if the embedded codec is bmp or png and create the codec
        std::unique_ptr<SkCodec> codec;
        Result dummyResult;
        if (SkPngCodec::IsPng((const char*) data->bytes(), data->size())) {
            codec = SkPngCodec::MakeFromStream(std::move(embeddedStream), &dummyResult);
        } else {
            codec = SkBmpCodec::MakeFromIco(std::move(embeddedStream), &dummyResult);
        }

        // Save a valid codec
        if (nullptr != codec) {
            codecs->push_back().reset(codec.release());
        }
    }

    // Recognize if there are no valid codecs
    if (0 == codecs->count()) {
        SkCodecPrintf("Error: could not find any valid embedded ico codecs.\n");
        return nullptr;
    }

    // Use the largest codec as a "suggestion" for image info
    size_t maxSize = 0;
    int maxIndex = 0;
    for (int i = 0; i < codecs->count(); i++) {
        SkImageInfo info = codecs->operator[](i)->getInfo();
        size_t size = info.computeMinByteSize();

        if (size > maxSize) {
            maxSize = size;
            maxIndex = i;
        }
    }

    auto maxInfo = codecs->operator[](maxIndex)->getEncodedInfo().copy();

    *result = kSuccess;
    // The original stream is no longer needed, because the embedded codecs own their
    // own streams.
    return std::unique_ptr<SkCodec>(new SkIcoCodec(std::move(maxInfo), codecs.release()));
}