path: root/Source/WebCore/platform/graphics/skia/ImageSkia.cpp

/*
 * Copyright (c) 2008, Google Inc. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"

#include "AffineTransform.h"
#include "BitmapImage.h"
#include "BitmapImageSingleFrameSkia.h"
#include "FloatConversion.h"
#include "FloatRect.h"
#include "GraphicsContext.h"
#include "ImageObserver.h"
#include "Logging.h"
#include "NativeImageSkia.h"
#include "PlatformContextSkia.h"
#include "SkBitmap.h"
#include "SkPixelRef.h"
#include "SkRect.h"
#include "SkShader.h"
#include "SkiaUtils.h"
#include "Texture.h"
#include <wtf/text/WTFString.h>

#include "skia/ext/image_operations.h"
#include "skia/ext/platform_canvas.h"

#include <limits>
#include <math.h>

#if PLATFORM(CHROMIUM)
#include "TraceEvent.h"
#endif

namespace WebCore {

// Used by computeResamplingMode to tell how bitmaps should be resampled.
enum ResamplingMode {
    // Nearest neighbor resampling. Used when we detect that the page is
    // trying to make a pattern by stretching a small bitmap very large.
    RESAMPLE_NONE,

    // Default skia resampling. Used for large growing of images where high
    // quality resampling doesn't get us very much except a slowdown.
    RESAMPLE_LINEAR,

    // High quality resampling.
    RESAMPLE_AWESOME,
};

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 limitResamplingMode(PlatformContextSkia* platformContext, ResamplingMode resampling)
{
    switch (platformContext->interpolationQuality()) {
    case InterpolationNone:
        return RESAMPLE_NONE;
    case InterpolationMedium:
        // For now we treat InterpolationMedium and InterpolationLow the same.
    case InterpolationLow:
        if (resampling == RESAMPLE_AWESOME)
            return RESAMPLE_LINEAR;
        break;
    case InterpolationHigh:
    case InterpolationDefault:
        break;
    }

    return resampling;
}

// Return true if the rectangle is aligned to integer boundaries.
// See comments for computeBitmapDrawRects() for how this is used.
static bool areBoundariesIntegerAligned(const SkRect& rect)
{
    // Value is 1.19209e-007. This is the tolerance threshold.
    const float epsilon = std::numeric_limits<float>::epsilon();
    SkIRect roundedRect = roundedIntRect(rect);

    return fabs(rect.x() - roundedRect.x()) < epsilon
        && fabs(rect.y() - roundedRect.y()) < epsilon
        && fabs(rect.right() - roundedRect.right()) < epsilon
        && fabs(rect.bottom() - roundedRect.bottom()) < epsilon;
}

// FIXME: Remove this code when SkCanvas accepts SkRect as source rectangle.
// See crbug.com/117597 for background.
//
// WebKit wants to draw a sub-rectangle (FloatRect) in a bitmap and scale it to
// another FloatRect. However Skia only allows bitmap to be addressed by a
// IntRect. This function computes the appropriate IntRect that encloses the
// source rectangle and the corresponding enclosing destination rectangle,
// while maintaining the scale factor.
//
// |srcRect| is the source rectangle in the bitmap. Return true if fancy
// alignment is required. User of this function needs to clip to |dstRect|.
// Return false if clipping is not needed.
//
// |dstRect| is the input rectangle that |srcRect| is scaled to.
//
// |outSrcRect| and |outDstRect| are the corresponding output rectangles.
//
// ALGORITHM
//
// The objective is to (a) find an enclosing IntRect for the source rectangle
// and (b) the corresponding FloatRect in destination space.
//
// These are the steps performed:
//
// 1. IntRect enclosingSrcRect = enclosingIntRect(srcRect)
//
//    Compute the enclosing IntRect for |srcRect|. This ensures the bitmap
//    image is addressed with integer boundaries.
//
// 2. FloatRect enclosingDestRect = mapSrcToDest(enclosingSrcRect)
//
//    Map the enclosing source rectangle to destination coordinate space.
//
// The output will be enclosingSrcRect and enclosingDestRect from the
// algorithm above.
static bool computeBitmapDrawRects(const SkISize& bitmapSize, const SkRect& srcRect, const SkRect& dstRect, SkIRect* outSrcRect, SkRect* outDstRect)
{
    if (areBoundariesIntegerAligned(srcRect)) {
        *outSrcRect = roundedIntRect(srcRect);
        *outDstRect = dstRect;
        return false;
    }

    SkIRect bitmapRect = SkIRect::MakeSize(bitmapSize);
    SkIRect enclosingSrcRect = enclosingIntRect(srcRect);
    enclosingSrcRect.intersect(bitmapRect); // Clip to bitmap rectangle.
    SkRect enclosingDstRect;
    enclosingDstRect.set(enclosingSrcRect);
    SkMatrix transform;
    transform.setRectToRect(srcRect, dstRect, SkMatrix::kFill_ScaleToFit);
    transform.mapRect(&enclosingDstRect);
    *outSrcRect = enclosingSrcRect;
    *outDstRect = enclosingDstRect;
    return true;
}

// This function is used to scale an image and extract a scaled fragment.
//
// ALGORITHM
//
// Because the scaled image size has to be integers, we approximate the real
// scale with the following formula (only X direction is shown):
//
// scaledImageWidth = round(scaleX * imageRect.width())
// approximateScaleX = scaledImageWidth / imageRect.width()
//
// With this method we maintain a constant scale factor among fragments in
// the scaled image. This allows fragments to stitch together to form the
// full scaled image. The downside is there will be a small difference
// between |scaleX| and |approximateScaleX|.
//
// A scaled image fragment is identified by:
//
// - Scaled image size
// - Scaled image fragment rectangle (IntRect)
//
// Scaled image size has been determined and the next step is to compute the
// rectangle for the scaled image fragment which needs to be an IntRect.
//
// scaledSrcRect = srcRect * (approximateScaleX, approximateScaleY)
// enclosingScaledSrcRect = enclosingIntRect(scaledSrcRect)
//
// Finally we extract the scaled image fragment using
// (scaledImageSize, enclosingScaledSrcRect).
//
static SkBitmap extractScaledImageFragment(const NativeImageSkia& bitmap, const SkRect& srcRect, float scaleX, float scaleY, SkRect* scaledSrcRect, SkIRect* enclosingScaledSrcRect)
{
    SkISize imageSize = SkISize::Make(bitmap.bitmap().width(), bitmap.bitmap().height());
    SkISize scaledImageSize = SkISize::Make(clampToInteger(roundf(imageSize.width() * scaleX)),
        clampToInteger(roundf(imageSize.height() * scaleY)));

    SkRect imageRect = SkRect::MakeWH(imageSize.width(), imageSize.height());
    SkRect scaledImageRect = SkRect::MakeWH(scaledImageSize.width(), scaledImageSize.height());

    SkMatrix scaleTransform;
    scaleTransform.setRectToRect(imageRect, scaledImageRect, SkMatrix::kFill_ScaleToFit);
    scaleTransform.mapRect(scaledSrcRect, srcRect);

    scaledSrcRect->intersect(scaledImageRect);
    *enclosingScaledSrcRect = enclosingIntRect(*scaledSrcRect);

    // |enclosingScaledSrcRect| can be larger than |scaledImageSize| because
    // of float inaccuracy so clip to get inside.
    enclosingScaledSrcRect->intersect(SkIRect::MakeSize(scaledImageSize));
    return bitmap.resizedBitmap(scaledImageSize, *enclosingScaledSrcRect);
}

// This does a lot of computation to resample only the portion of the bitmap
// that will only be drawn. This is critical for performance since when we are
// scrolling, for example, we are only drawing a small strip of the image.
// Resampling the whole image every time is very slow, so this speeds up things
// dramatically.
//
// Note: this code is only used when the canvas transformation is limited to
// scaling or translation.
static void drawResampledBitmap(SkCanvas& canvas, SkPaint& paint, const NativeImageSkia& bitmap, const SkRect& srcRect, const SkRect& destRect)
{
#if PLATFORM(CHROMIUM)
    TRACE_EVENT0("skia", "drawResampledBitmap");
#endif
    // We want to scale |destRect| with transformation in the canvas to obtain
    // the final scale. The final scale is a combination of scale transform
    // in canvas and explicit scaling (srcRect and destRect).
    SkRect screenRect;
    canvas.getTotalMatrix().mapRect(&screenRect, destRect);
    float realScaleX = screenRect.width() / srcRect.width();
    float realScaleY = screenRect.height() / srcRect.height();

    // This part of code limits scaling only to visible portion in the
    SkRect destRectVisibleSubset;
    ClipRectToCanvas(canvas, destRect, &destRectVisibleSubset);

    // ClipRectToCanvas often overshoots, resulting in a larger region than our
    // original destRect. Intersecting gets us back inside.
    if (!destRectVisibleSubset.intersect(destRect))
        return; // Nothing visible in destRect.

    // Find the corresponding rect in the source image.
    SkMatrix destToSrcTransform;
    SkRect srcRectVisibleSubset;
    destToSrcTransform.setRectToRect(destRect, srcRect, SkMatrix::kFill_ScaleToFit);
    destToSrcTransform.mapRect(&srcRectVisibleSubset, destRectVisibleSubset);

    SkRect scaledSrcRect;
    SkIRect enclosingScaledSrcRect;
    SkBitmap scaledImageFragment = extractScaledImageFragment(bitmap, srcRectVisibleSubset, realScaleX, realScaleY, &scaledSrcRect, &enclosingScaledSrcRect);

    // Expand the destination rectangle because the source rectangle was
    // expanded to fit to integer boundaries.
    SkMatrix scaledSrcToDestTransform;
    scaledSrcToDestTransform.setRectToRect(scaledSrcRect, destRectVisibleSubset, SkMatrix::kFill_ScaleToFit);
    SkRect enclosingDestRect;
    enclosingDestRect.set(enclosingScaledSrcRect);
    scaledSrcToDestTransform.mapRect(&enclosingDestRect);

    // The reason we do clipping is because Skia doesn't support SkRect as
    // source rect. See http://crbug.com/145540.
    // When Skia supports then use this as the source rect to replace 0.
    //
    // scaledSrcRect.offset(-enclosingScaledSrcRect.x(), -enclosingScaledSrcRect.y());
    canvas.save();
    canvas.clipRect(destRectVisibleSubset);

    // Because the image fragment is generated with an approxmiated scaling
    // factor. This draw will perform a close to 1 scaling.
    //
    // NOTE: For future optimization. If the difference in scale is so small
    // that Skia doesn't produce a difference then we can just blit it directly
    // to enhance performance.
    canvas.drawBitmapRect(scaledImageFragment, 0, enclosingDestRect, &paint);
    canvas.restore();
}

static bool hasNon90rotation(PlatformContextSkia* context)
{
    return !context->canvas()->getTotalMatrix().rectStaysRect();
}

static void paintSkBitmap(PlatformContextSkia* platformContext, const NativeImageSkia& bitmap, const SkRect& srcRect, const SkRect& destRect, const SkXfermode::Mode& compOp)
{
#if PLATFORM(CHROMIUM)
    TRACE_EVENT0("skia", "paintSkBitmap");
#endif
    SkPaint paint;
    paint.setXfermodeMode(compOp);
    paint.setAlpha(platformContext->getNormalizedAlpha());
    paint.setLooper(platformContext->getDrawLooper());
    // only antialias if we're rotated or skewed
    paint.setAntiAlias(hasNon90rotation(platformContext));

    SkCanvas* canvas = platformContext->canvas();

    ResamplingMode resampling;
    if (platformContext->isAccelerated())
        resampling = RESAMPLE_LINEAR;
    else if (platformContext->printing())
        resampling = RESAMPLE_NONE;
    else {
        // Take into account scale applied to the canvas when computing sampling mode (e.g. CSS scale or page scale).
        SkRect destRectTarget = destRect;
        if (!(canvas->getTotalMatrix().getType() & (SkMatrix::kAffine_Mask | SkMatrix::kPerspective_Mask)))
            canvas->getTotalMatrix().mapRect(&destRectTarget, destRect);

        resampling = computeResamplingMode(canvas->getTotalMatrix(), bitmap,
            SkScalarToFloat(srcRect.width()), SkScalarToFloat(srcRect.height()),
            SkScalarToFloat(destRectTarget.width()), SkScalarToFloat(destRectTarget.height()));
    }

    if (resampling == RESAMPLE_NONE) {
      // FIXME: This is to not break tests (it results in the filter bitmap flag
      // being set to true). We need to decide if we respect RESAMPLE_NONE
      // being returned from computeResamplingMode.
        resampling = RESAMPLE_LINEAR;
    }
    resampling = limitResamplingMode(platformContext, resampling);
    paint.setFilterBitmap(resampling == RESAMPLE_LINEAR);
    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.
        SkIRect enclosingSrcRect;
        SkRect enclosingDestRect;
        SkISize bitmapSize = SkISize::Make(bitmap.bitmap().width(), bitmap.bitmap().height());
        bool needsClipping = computeBitmapDrawRects(bitmapSize, srcRect, destRect, &enclosingSrcRect, &enclosingDestRect);

        if (enclosingSrcRect.isEmpty() || enclosingDestRect.isEmpty())
            return;

        // If destination is enlarged because source rectangle didn't align to
        // integer boundaries then we draw a slightly larger rectangle and clip
        // to the original destination rectangle.
        // See http://crbug.com/145540.
        if (needsClipping) {
            platformContext->save();
            platformContext->canvas()->clipRect(destRect);
        }

        canvas->drawBitmapRect(bitmap.bitmap(), &enclosingSrcRect, enclosingDestRect, &paint);

        if (needsClipping)
            platformContext->restore();
    }
    platformContext->didDrawRect(destRect, paint, &bitmap.bitmap());
}

// A helper method for translating negative width and height values.
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;
}

void Image::drawPattern(GraphicsContext* context,
                        const FloatRect& floatSrcRect,
                        const AffineTransform& patternTransform,
                        const FloatPoint& phase,
                        ColorSpace styleColorSpace,
                        CompositeOperator compositeOp,
                        const FloatRect& destRect)
{
#if PLATFORM(CHROMIUM)
    TRACE_EVENT0("skia", "Image::drawPattern");
#endif
    FloatRect normSrcRect = normalizeRect(floatSrcRect);
    if (destRect.isEmpty() || normSrcRect.isEmpty())
        return; // nothing to draw

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

    SkMatrix ctm = context->platformContext()->canvas()->getTotalMatrix();
    SkMatrix totalMatrix;
    totalMatrix.setConcat(ctm, patternTransform);

    // 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 big it will be.
    SkRect destRectTarget;
    totalMatrix.mapRect(&destRectTarget, normSrcRect);

    float destBitmapWidth = SkScalarToFloat(destRectTarget.width());
    float destBitmapHeight = SkScalarToFloat(destRectTarget.height());

    // Compute the resampling mode.
    ResamplingMode resampling;
    if (context->platformContext()->isAccelerated() || context->platformContext()->printing())
        resampling = RESAMPLE_LINEAR;
    else
        resampling = computeResamplingMode(totalMatrix, *bitmap, normSrcRect.width(), normSrcRect.height(), destBitmapWidth, destBitmapHeight);
    resampling = limitResamplingMode(context->platformContext(), resampling);

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

    SkShader* shader;
    if (resampling == RESAMPLE_AWESOME) {
        // Do nice resampling.
        float scaleX = destBitmapWidth / normSrcRect.width();
        float scaleY = destBitmapHeight / normSrcRect.height();
        SkRect scaledSrcRect;
        SkIRect enclosingScaledSrcRect;

        // The image fragment generated here is not exactly what is
        // requested. The scale factor used is approximated and image
        // fragment is slightly larger to align to integer
        // boundaries.
        SkBitmap resampled = extractScaledImageFragment(*bitmap, normSrcRect, scaleX, scaleY, &scaledSrcRect, &enclosingScaledSrcRect);
        shader = SkShader::CreateBitmapShader(resampled, SkShader::kRepeat_TileMode, SkShader::kRepeat_TileMode);

        // Since we just resized the bitmap, we need to remove the scale
        // applied to the pixels in the bitmap shader. This means we need
        // CTM * patternTransform to have identity scale. Since we
        // can't modify CTM (or the rectangle will be drawn in the wrong
        // place), we must set patternTransform's scale to the inverse of
        // CTM scale.
        matrix.setScaleX(ctm.getScaleX() ? 1 / ctm.getScaleX() : 1);
        matrix.setScaleY(ctm.getScaleY() ? 1 / ctm.getScaleY() : 1);
    } else {
        // No need to do nice resampling.
        SkBitmap srcSubset;
        bitmap->bitmap().extractSubset(&srcSubset, enclosingIntRect(normSrcRect));
        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() + normSrcRect.x() *
                      narrowPrecisionToFloat(patternTransform.a());
    float adjustedY = phase.y() + normSrcRect.y() *
                      narrowPrecisionToFloat(patternTransform.d());
    matrix.postTranslate(SkFloatToScalar(adjustedX),
                         SkFloatToScalar(adjustedY));
    shader->setLocalMatrix(matrix);

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

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

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

// FIXME: These should go to BitmapImageSkia.cpp

void BitmapImage::invalidatePlatformData()
{
}

void BitmapImage::checkForSolidColor()
{
    m_isSolidColor = false;
    m_checkedForSolidColor = true;

    if (frameCount() > 1)
        return;

    WebCore::NativeImageSkia* frame = frameAtIndex(0);

    if (frame && size().width() == 1 && size().height() == 1) {
        SkAutoLockPixels lock(frame->bitmap());
        if (!frame->bitmap().getPixels())
            return;

        m_isSolidColor = true;
        m_solidColor = Color(frame->bitmap().getColor(0, 0));
    }
}

void BitmapImage::draw(GraphicsContext* ctxt, const FloatRect& dstRect,
                       const FloatRect& srcRect, ColorSpace colorSpace, 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();

    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,
        normSrcRect,
        normDstRect,
        WebCoreCompositeToSkiaComposite(compositeOp));

    if (ImageObserver* observer = imageObserver())
        observer->didDraw(this);
}

// FIXME: These should go into BitmapImageSingleFrameSkia.cpp

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

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

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

    if (ImageObserver* observer = imageObserver())
        observer->didDraw(this);
}

BitmapImageSingleFrameSkia::BitmapImageSingleFrameSkia(const SkBitmap& bitmap, float resolutionScale)
    : m_nativeImage(bitmap, resolutionScale)
{
}

PassRefPtr<BitmapImageSingleFrameSkia> BitmapImageSingleFrameSkia::create(const SkBitmap& bitmap, bool copyPixels, float resolutionScale)
{
    if (copyPixels) {
        SkBitmap temp;
        if (!bitmap.deepCopyTo(&temp, bitmap.config()))
            bitmap.copyTo(&temp, bitmap.config());
        return adoptRef(new BitmapImageSingleFrameSkia(temp, resolutionScale));
    }
    return adoptRef(new BitmapImageSingleFrameSkia(bitmap, resolutionScale));
}

} // namespace WebCore