C++ HTMLCanvasElement::buffer方法代码示例

void GraphicsContext3D::paintRenderingResultsToCanvas(CanvasRenderingContext* context, DrawingBuffer*)
{
    HTMLCanvasElement* canvas = context->canvas();
    ImageBuffer* imageBuffer = canvas->buffer();

    int rowBytes = m_currentWidth * 4;
    int totalBytes = rowBytes * m_currentHeight;

    OwnArrayPtr<unsigned char> pixels = adoptArrayPtr(new unsigned char[totalBytes]);
    if (!pixels)
        return;

    readRenderingResults(pixels.get(), totalBytes);

    if (!m_attrs.premultipliedAlpha) {
        for (int i = 0; i < totalBytes; i += 4) {
            // Premultiply alpha.
            pixels[i + 0] = std::min(255, pixels[i + 0] * pixels[i + 3] / 255);
            pixels[i + 1] = std::min(255, pixels[i + 1] * pixels[i + 3] / 255);
            pixels[i + 2] = std::min(255, pixels[i + 2] * pixels[i + 3] / 255);
        }
    }

    paintToCanvas(pixels.get(), m_currentWidth, m_currentHeight,
                  canvas->width(), canvas->height(), imageBuffer->context()->platformContext());
}

PassRefPtr<Image> CSSCanvasValue::image(RenderObject* renderer, const IntSize& /*size*/)
{
    ASSERT(clients().contains(renderer));
    HTMLCanvasElement* elt = element(renderer->document());
    if (!elt || !elt->buffer())
        return 0;
    return elt->copiedImage();
}

void GraphicsContext3DInternal::paintRenderingResultsToCanvas(CanvasRenderingContext* context)
{
    HTMLCanvasElement* canvas = context->canvas();
    ImageBuffer* imageBuffer = canvas->buffer();
    unsigned char* pixels = 0;
#if PLATFORM(SKIA)
    const SkBitmap* canvasBitmap = imageBuffer->context()->platformContext()->bitmap();
    const SkBitmap* readbackBitmap = 0;
    ASSERT(canvasBitmap->config() == SkBitmap::kARGB_8888_Config);
    if (canvasBitmap->width() == m_impl->width() && canvasBitmap->height() == m_impl->height()) {
        // This is the fastest and most common case. We read back
        // directly into the canvas's backing store.
        readbackBitmap = canvasBitmap;
        m_resizingBitmap.reset();
    } else {
        // We need to allocate a temporary bitmap for reading back the
        // pixel data. We will then use Skia to rescale this bitmap to
        // the size of the canvas's backing store.
        if (m_resizingBitmap.width() != m_impl->width() || m_resizingBitmap.height() != m_impl->height()) {
            m_resizingBitmap.setConfig(SkBitmap::kARGB_8888_Config,
                                       m_impl->width(),
                                       m_impl->height());
            if (!m_resizingBitmap.allocPixels())
                return;
        }
        readbackBitmap = &m_resizingBitmap;
    }

    // Read back the frame buffer.
    SkAutoLockPixels bitmapLock(*readbackBitmap);
    pixels = static_cast<unsigned char*>(readbackBitmap->getPixels());
#elif PLATFORM(CG)
    if (m_renderOutput)
        pixels = m_renderOutput;
#else
#error Must port to your platform
#endif

    m_impl->readBackFramebuffer(pixels, 4 * m_impl->width() * m_impl->height());

#if PLATFORM(SKIA)
    if (m_resizingBitmap.readyToDraw()) {
        // We need to draw the resizing bitmap into the canvas's backing store.
        SkCanvas canvas(*canvasBitmap);
        SkRect dst;
        dst.set(SkIntToScalar(0), SkIntToScalar(0), SkIntToScalar(canvasBitmap->width()), SkIntToScalar(canvasBitmap->height()));
        canvas.drawBitmapRect(m_resizingBitmap, 0, dst);
    }
#elif PLATFORM(CG)
    if (m_renderOutput && context->is3d()) {
        WebGLRenderingContext* webGLContext = static_cast<WebGLRenderingContext*>(context);
        webGLContext->graphicsContext3D()->paintToCanvas(m_renderOutput, m_impl->width(), m_impl->height(), canvas->width(), canvas->height(), imageBuffer->context()->platformContext());
    }
#else
#error Must port to your platform
#endif
}

void GraphicsContext3D::paintRenderingResultsToCanvas(CanvasRenderingContext* context)
{
    HTMLCanvasElement* canvas = context->canvas();
    ImageBuffer* imageBuffer = canvas->buffer();

    int rowBytes = m_currentWidth * 4;
    int totalBytes = rowBytes * m_currentHeight;

    OwnArrayPtr<unsigned char> pixels = adoptArrayPtr(new unsigned char[totalBytes]);
    if (!pixels)
        return;

    makeContextCurrent();

    bool mustRestoreFBO = false;
    if (m_attrs.antialias) {
        ::glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, m_multisampleFBO);
        ::glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, m_fbo);
        ::glBlitFramebufferEXT(0, 0, m_currentWidth, m_currentHeight, 0, 0, m_currentWidth, m_currentHeight, GL_COLOR_BUFFER_BIT, GL_LINEAR);
        ::glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_fbo);
        mustRestoreFBO = true;
    } else {
        if (m_boundFBO != m_fbo) {
            mustRestoreFBO = true;
            ::glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_fbo);
        }
    }

    GLint packAlignment = 4;
    bool mustRestorePackAlignment = false;
    ::glGetIntegerv(GL_PACK_ALIGNMENT, &packAlignment);
    if (packAlignment > 4) {
        ::glPixelStorei(GL_PACK_ALIGNMENT, 4);
        mustRestorePackAlignment = true;
    }

    ::glReadPixels(0, 0, m_currentWidth, m_currentHeight, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, pixels.get());

    if (mustRestorePackAlignment)
        ::glPixelStorei(GL_PACK_ALIGNMENT, packAlignment);

    if (mustRestoreFBO)
        ::glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_boundFBO);

    paintToCanvas(pixels.get(), m_currentWidth, m_currentHeight,
                  canvas->width(), canvas->height(), imageBuffer->context()->platformContext());
}