imageskia.cpp

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        computeResamplingMode(bitmap, srcRect.width(), srcRect.height(),
                              SkScalarToFloat(destRect.width()),
                              SkScalarToFloat(destRect.height()));
    if (resampling == RESAMPLE_AWESOME) {
        drawResampledBitmap(*canvas, paint, bitmap, srcRect, destRect);
    } else {
        // No resampling necessary, we can just draw the bitmap. We want to
        // filter it if we decided to do linear interpolation above, or if there
        // is something interesting going on with the matrix (like a rotation).
        // Note: for serialization, we will want to subset the bitmap first so
        // we don't send extra pixels.
        canvas->drawBitmapRect(bitmap, &srcRect, destRect, &paint);
    }
}

// Transforms the given dimensions with the given matrix. Used to see how big
// images will be once transformed.
static void TransformDimensions(const SkMatrix& matrix, float srcWidth, float srcHeight, float* destWidth, float* destHeight) {
    // Transform 3 points to see how long each side of the bitmap will be.
    SkPoint src_points[3];  // (0, 0), (width, 0), (0, height).
    src_points[0].set(0, 0);
    src_points[1].set(SkFloatToScalar(srcWidth), 0);
    src_points[2].set(0, SkFloatToScalar(srcHeight));

    // Now measure the length of the two transformed vectors relative to the
    // transformed origin to see how big the bitmap will be. Note: for skews,
    // this isn't the best thing, but we don't have skews.
    SkPoint dest_points[3];
    matrix.mapPoints(dest_points, src_points, 3);
    *destWidth = SkScalarToFloat((dest_points[1] - dest_points[0]).length());
    *destHeight = SkScalarToFloat((dest_points[2] - dest_points[0]).length());
}

// A helper method for translating negative width and height values.
static FloatRect normalizeRect(const FloatRect& rect)
{
    FloatRect norm = rect;
    if (norm.width() < 0) {
        norm.setX(norm.x() + norm.width());
        norm.setWidth(-norm.width());
    }
    if (norm.height() < 0) {
        norm.setY(norm.y() + norm.height());
        norm.setHeight(-norm.height());
    }
    return norm;
}

bool FrameData::clear(bool clearMetadata)
{
    if (clearMetadata)
        m_haveMetadata = false;

    if (m_frame) {
        // ImageSource::createFrameAtIndex() allocated |m_frame| and passed
        // ownership to BitmapImage; we must delete it here.
        delete m_frame;
        m_frame = 0;
        return true;
    }
    return false;
}

PassRefPtr<Image> Image::loadPlatformResource(const char *name)
{
    return ChromiumBridge::loadPlatformImageResource(name);
}

void Image::drawPattern(GraphicsContext* context,
                        const FloatRect& floatSrcRect,
                        const TransformationMatrix& patternTransform,
                        const FloatPoint& phase,
                        CompositeOperator compositeOp,
                        const FloatRect& destRect)
{
    if (destRect.isEmpty() || floatSrcRect.isEmpty())
        return;  // nothing to draw

    NativeImageSkia* bitmap = nativeImageForCurrentFrame();
    if (!bitmap)
        return;

    // This is a very inexpensive operation. It will generate a new bitmap but
    // it will internally reference the old bitmap's pixels, adjusting the row
    // stride so the extra pixels appear as padding to the subsetted bitmap.
    SkBitmap srcSubset;
    SkIRect srcRect = enclosingIntRect(floatSrcRect);
    bitmap->extractSubset(&srcSubset, srcRect);

    SkBitmap resampled;
    SkShader* shader;

    // Figure out what size the bitmap will be in the destination. The
    // destination rect is the bounds of the pattern, we need to use the
    // matrix to see how bit it will be.
    float destBitmapWidth, destBitmapHeight;
    TransformDimensions(patternTransform, srcRect.width(), srcRect.height(),
                        &destBitmapWidth, &destBitmapHeight);

    // Compute the resampling mode.
    ResamplingMode resampling;
    if (context->platformContext()->isPrinting())
      resampling = RESAMPLE_LINEAR;
    else {
      resampling = computeResamplingMode(*bitmap,
                                         srcRect.width(), srcRect.height(),
                                         destBitmapWidth, destBitmapHeight);
    }

    // Load the transform WebKit requested.
    SkMatrix matrix(patternTransform);

    if (resampling == RESAMPLE_AWESOME) {
        // Do nice resampling.
        SkBitmap resampled = skia::ImageOperations::Resize(srcSubset,
            skia::ImageOperations::RESIZE_LANCZOS3,
            static_cast<int>(destBitmapWidth),
            static_cast<int>(destBitmapHeight));
        shader = SkShader::CreateBitmapShader(resampled, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode);

        // Since we just resized the bitmap, we need to undo the scale set in
        // the image transform.
        matrix.setScaleX(SkIntToScalar(1));
        matrix.setScaleY(SkIntToScalar(1));
    } else {
        // No need to do nice resampling.
        shader = SkShader::CreateBitmapShader(srcSubset, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode);
    }

    // We also need to translate it such that the origin of the pattern is the
    // origin of the destination rect, which is what WebKit expects. Skia uses
    // the coordinate system origin as the base for the patter. If WebKit wants
    // a shifted image, it will shift it from there using the patternTransform.
    float adjustedX = phase.x() + floatSrcRect.x() *
                      narrowPrecisionToFloat(patternTransform.a());
    float adjustedY = phase.y() + floatSrcRect.y() *
                      narrowPrecisionToFloat(patternTransform.d());
    matrix.postTranslate(SkFloatToScalar(adjustedX),
                         SkFloatToScalar(adjustedY));
    shader->setLocalMatrix(matrix);

    SkPaint paint;
    paint.setShader(shader)->unref();
    paint.setPorterDuffXfermode(WebCoreCompositeToSkiaComposite(compositeOp));
    paint.setFilterBitmap(resampling == RESAMPLE_LINEAR);

    context->platformContext()->paintSkPaint(destRect, paint);
}

// ================================================
// BitmapImage Class
// ================================================

// FIXME: These should go to BitmapImageSkia.cpp

void BitmapImage::initPlatformData()
{
    // This is not used. On Mac, the "platform" data is a cache of some OS
    // specific versions of the image that are created is some cases. These
    // aren't normally used, it is equivalent to getHBITMAP on Windows, and
    // the platform data is the cache.
}

void BitmapImage::invalidatePlatformData()
{
    // See initPlatformData above.
}

void BitmapImage::checkForSolidColor()
{
    m_checkedForSolidColor = true;
}

void BitmapImage::draw(GraphicsContext* ctxt, const FloatRect& dstRect,
                       const FloatRect& srcRect, CompositeOperator compositeOp)
{
    if (!m_source.initialized())
        return;

    // Spin the animation to the correct frame before we try to draw it, so we
    // don't draw an old frame and then immediately need to draw a newer one,
    // causing flicker and wasting CPU.
    startAnimation();

    const NativeImageSkia* bm = nativeImageForCurrentFrame();
    if (!bm)
        return;  // It's too early and we don't have an image yet.

    FloatRect normDstRect = normalizeRect(dstRect);
    FloatRect normSrcRect = normalizeRect(srcRect);

    if (normSrcRect.isEmpty() || normDstRect.isEmpty())
        return;  // Nothing to draw.

    paintSkBitmap(ctxt->platformContext(),
                  *bm,
                  enclosingIntRect(normSrcRect),
                  enclosingIntRect(normDstRect),
                  WebCoreCompositeToSkiaComposite(compositeOp));
}

// FIXME: These should go into BitmapImageSingleFrameSkia.cpp

void BitmapImageSingleFrameSkia::draw(GraphicsContext* ctxt,
                                      const FloatRect& dstRect,
                                      const FloatRect& srcRect,
                                      CompositeOperator compositeOp)
{
    FloatRect normDstRect = normalizeRect(dstRect);
    FloatRect normSrcRect = normalizeRect(srcRect);

    if (normSrcRect.isEmpty() || normDstRect.isEmpty())
        return;  // Nothing to draw.

    paintSkBitmap(ctxt->platformContext(),
                  m_nativeImage,
                  enclosingIntRect(normSrcRect),
                  enclosingIntRect(normDstRect),
                  WebCoreCompositeToSkiaComposite(compositeOp));
}

PassRefPtr<BitmapImageSingleFrameSkia> BitmapImageSingleFrameSkia::create(const SkBitmap& bitmap)
{
    RefPtr<BitmapImageSingleFrameSkia> image(adoptRef(new BitmapImageSingleFrameSkia()));
    if (!bitmap.copyTo(&image->m_nativeImage, bitmap.config()))
        return 0;
    return image.release();
}

}  // namespace WebCore