Source/WebCore/platform/graphics/ImageBufferBackend.cpp

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#include "config.h"
#include "ImageBufferBackend.h"

#include "GraphicsContext.h"
#include "Image.h"
#include "PixelBuffer.h"
#include "PixelBufferConversion.h"

namespace WebCore {

IntSize ImageBufferBackend::calculateBackendSize(const Parameters& parameters)
{
    FloatSize scaledSize = { ceilf(parameters.resolutionScale * parameters.logicalSize.width()), ceilf(parameters.resolutionScale * parameters.logicalSize.height()) };
    if (scaledSize.isEmpty() || !scaledSize.isExpressibleAsIntSize())
        return { };

    return IntSize(scaledSize);
}

size_t ImageBufferBackend::calculateMemoryCost(const IntSize& backendSize, unsigned bytesPerRow)
{
    ASSERT(!backendSize.isEmpty());
    return CheckedUint32(backendSize.height()) * bytesPerRow;
}

ImageBufferBackend::ImageBufferBackend(const Parameters& parameters)
    : m_parameters(parameters)
{
}

ImageBufferBackend::~ImageBufferBackend() = default;

RefPtr<NativeImage> ImageBufferBackend::sinkIntoNativeImage()
{
    return copyNativeImage(DontCopyBackingStore);
}

void ImageBufferBackend::convertToLuminanceMask()
{
    PixelBufferFormat format { AlphaPremultiplication::Unpremultiplied, PixelFormat::RGBA8, colorSpace() };
    auto pixelBuffer = getPixelBuffer(format, logicalRect());
    if (!pixelBuffer)
        return;

    unsigned pixelArrayLength = pixelBuffer->sizeInBytes();
    for (unsigned pixelOffset = 0; pixelOffset < pixelArrayLength; pixelOffset += 4) {
        uint8_t a = pixelBuffer->item(pixelOffset + 3);
        if (!a)
            continue;
        uint8_t r = pixelBuffer->item(pixelOffset);
        uint8_t g = pixelBuffer->item(pixelOffset + 1);
        uint8_t b = pixelBuffer->item(pixelOffset + 2);

        double luma = (r * 0.2125 + g * 0.7154 + b * 0.0721) * ((double)a / 255.0);
        pixelBuffer->set(pixelOffset + 3, luma);
    }

    putPixelBuffer(*pixelBuffer, logicalRect(), IntPoint::zero(), AlphaPremultiplication::Premultiplied);
}

RefPtr<PixelBuffer> ImageBufferBackend::getPixelBuffer(const PixelBufferFormat& destinationFormat, const IntRect& sourceRect, void* data, const ImageBufferAllocator& allocator) const
{
    ASSERT(PixelBuffer::supportedPixelFormat(destinationFormat.pixelFormat));

    auto sourceRectScaled = toBackendCoordinates(sourceRect);

    auto pixelBuffer = allocator.createPixelBuffer(destinationFormat, sourceRectScaled.size());
    if (!pixelBuffer)
        return nullptr;

    auto sourceRectClipped = intersection(backendRect(), sourceRectScaled);
    IntRect destinationRect { IntPoint::zero(), sourceRectClipped.size() };

    if (sourceRectScaled.x() < 0)
        destinationRect.setX(-sourceRectScaled.x());

    if (sourceRectScaled.y() < 0)
        destinationRect.setY(-sourceRectScaled.y());

    if (destinationRect.size() != sourceRectScaled.size())
        pixelBuffer->zeroFill();

    ConstPixelBufferConversionView source {
        { AlphaPremultiplication::Premultiplied, pixelFormat(), colorSpace() },
        bytesPerRow(),
        static_cast<uint8_t*>(data) + sourceRectClipped.y() * source.bytesPerRow + sourceRectClipped.x() * 4
    };
    
    PixelBufferConversionView destination {
        destinationFormat,
        static_cast<unsigned>(4 * sourceRectScaled.width()),
        pixelBuffer->bytes() + destinationRect.y() * destination.bytesPerRow + destinationRect.x() * 4
    };

    convertImagePixels(source, destination, destinationRect.size());

    return pixelBuffer;
}

void ImageBufferBackend::putPixelBuffer(const PixelBuffer& sourcePixelBuffer, const IntRect& sourceRect, const IntPoint& destinationPoint, AlphaPremultiplication destinationAlphaFormat, void* data)
{
    auto sourceRectScaled = toBackendCoordinates(sourceRect);
    auto destinationPointScaled = toBackendCoordinates(destinationPoint);

    auto sourceRectClipped = intersection({ IntPoint::zero(), sourcePixelBuffer.size() }, sourceRectScaled);
    auto destinationRect = sourceRectClipped;
    destinationRect.moveBy(destinationPointScaled);

    if (sourceRectScaled.x() < 0)
        destinationRect.setX(destinationRect.x() - sourceRectScaled.x());

    if (sourceRectScaled.y() < 0)
        destinationRect.setY(destinationRect.y() - sourceRectScaled.y());

    destinationRect.intersect(backendRect());
    sourceRectClipped.setSize(destinationRect.size());

    ConstPixelBufferConversionView source {
        sourcePixelBuffer.format(),
        static_cast<unsigned>(4 * sourcePixelBuffer.size().width()),
        sourcePixelBuffer.bytes() + sourceRectClipped.y() * source.bytesPerRow + sourceRectClipped.x() * 4
    };

    PixelBufferConversionView destination {
        { destinationAlphaFormat, pixelFormat(), colorSpace() },
        bytesPerRow(),
        static_cast<uint8_t*>(data) + destinationRect.y() * destination.bytesPerRow + destinationRect.x() * 4
    };

    convertImagePixels(source, destination, destinationRect.size());
}

AffineTransform ImageBufferBackend::calculateBaseTransform(const Parameters& parameters, bool originAtBottomLeftCorner)
{
    AffineTransform baseTransform;

    if (originAtBottomLeftCorner) {
        baseTransform.scale(1, -1);
        baseTransform.translate(0, -calculateBackendSize(parameters).height());
    }

    baseTransform.scale(parameters.resolutionScale);

    return baseTransform;
}

void ImageBufferBackend::applyBaseTransformToContext() const
{
    auto& context = this->context();
    context.applyDeviceScaleFactor(m_parameters.resolutionScale);
    context.setCTM(calculateBaseTransform(m_parameters, originAtBottomLeftCorner()));
}

} // namespace WebCore