vendor: OpenCV 5.0.0 snapshot at 755e50675d97db9b7d449d8bd6b09888646f6c6e

modules/viz/tutorials/creating_widgets/creating_widgets.markdown

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+Creating Widgets {#tutorial_creating_widgets}
+================
+
+@prev_tutorial{tutorial_transformations}
+@next_tutorial{tutorial_histo3D}
+
+Goal
+----
+
+In this tutorial you will learn how to
+
+-   Create your own widgets using WidgetAccessor and VTK.
+-   Show your widget in the visualization window.
+
+Code
+----
+
+You can download the code from [here ](https://github.com/opencv/opencv_contrib/tree/master/modules/viz/samples/creating_widgets.cpp).
+@include viz/samples/creating_widgets.cpp
+
+Explanation
+-----------
+
+Here is the general structure of the program:
+
+-   Extend Widget3D class to create a new 3D widget.
+    @code{.cpp}
+    class WTriangle : public viz::Widget3D
+    {
+        public:
+            WTriangle(const Point3f &pt1, const Point3f &pt2, const Point3f &pt3, const viz::Color & color = viz::Color::white());
+    };
+    @endcode
+-   Assign a VTK actor to the widget.
+    @code{.cpp}
+    // Store this actor in the widget in order that visualizer can access it
+    viz::WidgetAccessor::setProp(*this, actor);
+    @endcode
+-   Set color of the widget.
+    @code{.cpp}
+    // Set the color of the widget. This has to be called after WidgetAccessor.
+    setColor(color);
+    @endcode
+-   Construct a triangle widget and display it in the window.
+    @code{.cpp}
+    /// Create a triangle widget
+    WTriangle tw(Point3f(0.0,0.0,0.0), Point3f(1.0,1.0,1.0), Point3f(0.0,1.0,0.0), viz::Color::red());
+
+    /// Show widget in the visualizer window
+    myWindow.showWidget("TRIANGLE", tw);
+    @endcode
+
+Results
+-------
+
+Here is the result of the program.
+
+![](images/red_triangle.png)