CameraPositionWidget: a workaround for setting frustum color in the presence of an image

modules/viz/include/opencv2/viz/widgets.hpp

@@ -173,7 +173,7 @@ namespace cv
             CameraPositionWidget(const Vec3f &position, const Vec3f &look_at, const Vec3f &up_vector, double scale = 1.0);
             CameraPositionWidget(const Matx33f &K, double scale = 1.0, const Color &color = Color::white());
             CameraPositionWidget(const Vec2f &fov, double scale = 1.0, const Color &color = Color::white());
-            CameraPositionWidget(const Matx33f &K, const Mat &img, double scale = 1.0);
+            CameraPositionWidget(const Matx33f &K, const Mat &img, double scale = 1.0, const Color &color = Color::white());
             
         };
         

modules/viz/src/shape_widgets.cpp

@@ -1031,7 +1031,7 @@ cv::viz::CameraPositionWidget::CameraPositionWidget(const Vec2f &fov, double sca
     setColor(color);
 }
 
-cv::viz::CameraPositionWidget::CameraPositionWidget(const Matx33f &K, const Mat &image, double scale)
+cv::viz::CameraPositionWidget::CameraPositionWidget(const Matx33f &K, const Mat &image, double scale, const Color &color)
 {
     CV_Assert(!image.empty() && image.depth() == CV_8U);
     
@@ -1049,6 +1049,11 @@ cv::viz::CameraPositionWidget::CameraPositionWidget(const Matx33f &K, const Mat
     vtkSmartPointer<vtkImageData> vtk_image = vtkSmartPointer<vtkImageData>::New();
     ConvertToVtkImage::convert(image, vtk_image);
     
+    // Adjust a pixel of the vtk_image
+    vtk_image->SetScalarComponentFromDouble(0, image.rows-1, 0, 0, color[2]);
+    vtk_image->SetScalarComponentFromDouble(0, image.rows-1, 0, 1, color[1]);
+    vtk_image->SetScalarComponentFromDouble(0, image.rows-1, 0, 2, color[0]);
+    
     // Need to flip the image as the coordinates are different in OpenCV and VTK
     vtkSmartPointer<vtkImageFlip> flipFilter = vtkSmartPointer<vtkImageFlip>::New();
     flipFilter->SetFilteredAxis(1); // Vertical flip