C++ NativeImageSkia::isDataComplete方法代码示例

static void loadBufferingImageData()
{
    static bool loaded = false;
    if (!loaded) {
        static Image* bufferingIcon = Image::loadPlatformResource("vidbuffer").leakRef();
        NativeImageSkia* nativeImage = bufferingIcon->nativeImageForCurrentFrame();
        if (!nativeImage)
            return;

        if (!nativeImage->isDataComplete())
            return;

        loaded = true;
        nativeImage->bitmap().lockPixels();

        int bufSize = nativeImage->bitmap().width() * nativeImage->bitmap().height() * 4;
        s_bufferingImageWidth = nativeImage->bitmap().width();
        s_bufferingImageHeight = nativeImage->bitmap().height();
        s_bufferingImageData = static_cast<char*>(malloc(bufSize));
        memcpy(s_bufferingImageData, nativeImage->bitmap().getPixels(), bufSize);

        nativeImage->bitmap().unlockPixels();
        bufferingIcon->deref();
    }
}

static ResamplingMode computeResamplingMode(const SkMatrix& matrix, const NativeImageSkia& bitmap, float srcWidth, float srcHeight, float destWidth, float destHeight)
{
    // The percent change below which we will not resample. This usually means
    // an off-by-one error on the web page, and just doing nearest neighbor
    // sampling is usually good enough.
    const float kFractionalChangeThreshold = 0.025f;

    // Images smaller than this in either direction are considered "small" and
    // are not resampled ever (see below).
    const int kSmallImageSizeThreshold = 8;

    // The amount an image can be stretched in a single direction before we
    // say that it is being stretched so much that it must be a line or
    // background that doesn't need resampling.
    const float kLargeStretch = 3.0f;

    // Figure out if we should resample this image. We try to prune out some
    // common cases where resampling won't give us anything, since it is much
    // slower than drawing stretched.
    float diffWidth = fabs(destWidth - srcWidth);
    float diffHeight = fabs(destHeight - srcHeight);
    bool widthNearlyEqual = diffWidth < std::numeric_limits<float>::epsilon();
    bool heightNearlyEqual = diffHeight < std::numeric_limits<float>::epsilon();
    // We don't need to resample if the source and destination are the same.
    if (widthNearlyEqual && heightNearlyEqual)
        return RESAMPLE_NONE;

    if (srcWidth <= kSmallImageSizeThreshold
        || srcHeight <= kSmallImageSizeThreshold
        || destWidth <= kSmallImageSizeThreshold
        || destHeight <= kSmallImageSizeThreshold) {
        // Never resample small images. These are often used for borders and
        // rules (think 1x1 images used to make lines).
        return RESAMPLE_NONE;
    }

    if (srcHeight * kLargeStretch <= destHeight || srcWidth * kLargeStretch <= destWidth) {
        // Large image detected.

        // Don't resample if it is being stretched a lot in only one direction.
        // This is trying to catch cases where somebody has created a border
        // (which might be large) and then is stretching it to fill some part
        // of the page.
        if (widthNearlyEqual || heightNearlyEqual)
            return RESAMPLE_NONE;

        // The image is growing a lot and in more than one direction. Resampling
        // is slow and doesn't give us very much when growing a lot.
        return RESAMPLE_LINEAR;
    }

    if ((diffWidth / srcWidth < kFractionalChangeThreshold)
        && (diffHeight / srcHeight < kFractionalChangeThreshold)) {
        // It is disappointingly common on the web for image sizes to be off by
        // one or two pixels. We don't bother resampling if the size difference
        // is a small fraction of the original size.
        return RESAMPLE_NONE;
    }

    // When the image is not yet done loading, use linear. We don't cache the
    // partially resampled images, and as they come in incrementally, it causes
    // us to have to resample the whole thing every time.
    if (!bitmap.isDataComplete())
        return RESAMPLE_LINEAR;

    // Everything else gets resampled.
    // High quality interpolation only enabled for scaling and translation.
    if (!(matrix.getType() & (SkMatrix::kAffine_Mask | SkMatrix::kPerspective_Mask)))
        return RESAMPLE_AWESOME;
    
    return RESAMPLE_LINEAR;
}

static ResamplingMode computeResamplingMode(PlatformContextSkia* platformContext, const NativeImageSkia& bitmap, int srcWidth, int srcHeight, float destWidth, float destHeight)
{
    if (platformContext->hasImageResamplingHint()) {
        IntSize srcSize;
        FloatSize dstSize;
        platformContext->getImageResamplingHint(&srcSize, &dstSize);
        srcWidth = srcSize.width();
        srcHeight = srcSize.height();
        destWidth = dstSize.width();
        destHeight = dstSize.height();
    }

    int destIWidth = static_cast<int>(destWidth);
    int destIHeight = static_cast<int>(destHeight);

    // The percent change below which we will not resample. This usually means
    // an off-by-one error on the web page, and just doing nearest neighbor
    // sampling is usually good enough.
    const float kFractionalChangeThreshold = 0.025f;

    // Images smaller than this in either direction are considered "small" and
    // are not resampled ever (see below).
    const int kSmallImageSizeThreshold = 8;

    // The amount an image can be stretched in a single direction before we
    // say that it is being stretched so much that it must be a line or
    // background that doesn't need resampling.
    const float kLargeStretch = 3.0f;

    // Figure out if we should resample this image. We try to prune out some
    // common cases where resampling won't give us anything, since it is much
    // slower than drawing stretched.
    if (srcWidth == destIWidth && srcHeight == destIHeight) {
        // We don't need to resample if the source and destination are the same.
        return RESAMPLE_NONE;
    }

    if (srcWidth <= kSmallImageSizeThreshold
        || srcHeight <= kSmallImageSizeThreshold
        || destWidth <= kSmallImageSizeThreshold
        || destHeight <= kSmallImageSizeThreshold) {
        // Never resample small images. These are often used for borders and
        // rules (think 1x1 images used to make lines).
        return RESAMPLE_NONE;
    }

    if (srcHeight * kLargeStretch <= destHeight || srcWidth * kLargeStretch <= destWidth) {
        // Large image detected.

        // Don't resample if it is being stretched a lot in only one direction.
        // This is trying to catch cases where somebody has created a border
        // (which might be large) and then is stretching it to fill some part
        // of the page.
        if (srcWidth == destWidth || srcHeight == destHeight)
            return RESAMPLE_NONE;

        // The image is growing a lot and in more than one direction. Resampling
        // is slow and doesn't give us very much when growing a lot.
        return RESAMPLE_LINEAR;
    }

    if ((fabs(destWidth - srcWidth) / srcWidth < kFractionalChangeThreshold)
        && (fabs(destHeight - srcHeight) / srcHeight < kFractionalChangeThreshold)) {
        // It is disappointingly common on the web for image sizes to be off by
        // one or two pixels. We don't bother resampling if the size difference
        // is a small fraction of the original size.
        return RESAMPLE_NONE;
    }

    // When the image is not yet done loading, use linear. We don't cache the
    // partially resampled images, and as they come in incrementally, it causes
    // us to have to resample the whole thing every time.
    if (!bitmap.isDataComplete())
        return RESAMPLE_LINEAR;

    // Everything else gets resampled.
    // If the platform context permits high quality interpolation, use it.
    // High quality interpolation only enabled for scaling and translation.
    if (platformContext->interpolationQuality() == InterpolationHigh
        && !(platformContext->canvas()->getTotalMatrix().getType() & (SkMatrix::kAffine_Mask | SkMatrix::kPerspective_Mask)))
        return RESAMPLE_AWESOME;
    
    return RESAMPLE_LINEAR;
}