Method DrawLineGradient

IO/Export/vtkSVGContextDevice2D.cxx:2185–2222

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//------------------------------------------------------------------------------
void vtkSVGContextDevice2D::DrawLineGradient(const vtkVector2f& p1, const vtkColor4ub& c1,
  const vtkVector2f& p2, const vtkColor4ub& c2, bool useAlpha)
{
  const vtkColor4ub aveColor = { static_cast<unsigned char>(static_cast<int>(c1[0] + c2[0]) / 2),
    static_cast<unsigned char>(static_cast<int>(c1[1] + c2[1]) / 2),
    static_cast<unsigned char>(static_cast<int>(c1[2] + c2[2]) / 2),
    static_cast<unsigned char>(static_cast<int>(c1[3] + c2[3]) / 2) };

  // If the colors are more or less the same, go ahead and draw this segment.
  // Same if the segment is small enough to fit on a single pixel.
  if (this->LengthLessThanTolerance(p1, p2) || this->ColorsAreClose(c1, c2, useAlpha))
  {
    YConverter y(this->CanvasHeight);
    vtkNew<vtkXMLDataElement> line;
    this->ActiveNode->AddNestedElement(line);
    line->SetName("line");
    line->SetFloatAttribute("x1", p1[0]);
    line->SetFloatAttribute("y1", y(p1[1]));
    line->SetFloatAttribute("x2", p2[0]);
    line->SetFloatAttribute("y2", y(p2[1]));
    this->ApplyPenWidthToNode(line);
    line->SetAttribute("stroke", ColorToString(aveColor.GetData()).c_str());
    if (useAlpha && aveColor[3] != 255)
    {
      line->SetFloatAttribute("stroke-opacity", aveColor[3] / 255.f);
    }
    // FIXME: Disable gradient stipple for now, we'd need to account for offsets
    //  this->ApplyPenStippleToNode(node);

    return;
  }

  // Otherwise, subdivide into two more line segments:
  const vtkVector2f avePos = (p1 + p2) * 0.5;

  this->DrawLineGradient(p1, c1, avePos, aveColor, useAlpha);
  this->DrawLineGradient(avePos, aveColor, p2, c2, useAlpha);
}

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void vtkSVGContextDevice2D::DrawTriangleGradient(const vtkVector2f& p1, const vtkColor4ub& c1,