Method onDrawImageRect

src/pdf/PDFExportContext.cpp:759–881

}

void PDFExportContext::onDrawImageRect(std::shared_ptr<Image> image, const Rect& rect,
                                       const SamplingOptions& sampling, const MCState& state,
                                       const Fill& fill) {
  if (!image) {
    return;
  }

  // First, figure out the src->dst transform and subset the image if needed.
  auto bound = Rect::MakeWH(image->width(), image->height());
  float scaleX = rect.width() / bound.width();
  float scaleY = rect.height() / bound.height();
  float transX = rect.left - (bound.left * scaleX);
  float transY = rect.top - (bound.top * scaleY);
  auto transform = Matrix::I();
  transform.postScale(scaleX, scaleY);
  transform.postTranslate(transX, transY);

  // Alpha-only images need to get their color from the shader, before applying the colorfilter.
  auto modifiedFill = fill;
  if (image->isAlphaOnly() && modifiedFill.colorFilter) {
    // must blend alpha image and shader before applying colorfilter.
    auto surface = Surface::Make(document->context(), image->width(), image->height());
    Canvas* canvas = surface->getCanvas();
    Paint tmpPaint;
    // In the case of alpha images with shaders, the shader's coordinate system is the image's
    // coordiantes.
    tmpPaint.setShader(modifiedFill.shader);
    tmpPaint.setColor(modifiedFill.color);
    canvas->clear();
    canvas->drawImage(image, &tmpPaint);
    if (modifiedFill.shader != nullptr) {
      modifiedFill.shader = nullptr;
    }
    image = surface->makeImageSnapshot();
    DEBUG_ASSERT(!image->isAlphaOnly());
  }

  if (image->isAlphaOnly()) {
    // The ColorFilter applies to the paint color/shader, not the alpha layer.
    DEBUG_ASSERT(modifiedFill.colorFilter == nullptr);

    // PDF doesn't seem to allow masking vector graphics with an Image XObject. Must mask with a
    // Form XObject.
    auto maskContext = PDFExportContext(ISize::Make(image->width(), image->height()), document);
    {
      auto canvas = PDFDocumentImpl::MakeCanvas(&maskContext);
      // This clip prevents the mask image shader from covering entire device if unnecessary.
      canvas->clipRect(state.clip.getBounds());
      if (modifiedFill.maskFilter) {
        Paint tmpPaint;
        auto imageShader =
            Shader::MakeImageShader(image, TileMode::Clamp, TileMode::Clamp, SamplingOptions());
        imageShader = imageShader->makeWithMatrix(transform);
        tmpPaint.setShader(imageShader);
        tmpPaint.setMaskFilter(modifiedFill.maskFilter);
        canvas->drawRect(rect, tmpPaint);
      } else {
        canvas->concat(transform);