VTK vtkcontourwidget extracts regions of interest

vtkContourWidget brief introduction

It is mainly used to represent a point set , There are connections between point sets , Adjacent point , Not any point . The selection of the last point determines , Is the outline closed or open .
 

Use scenarios ：

It can usually be used to extract regions of interest ; See the picture

 

  official demo

#include <vtkCellArray.h>
#include <vtkContourWidget.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkMath.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkOrientedGlyphContourRepresentation.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

int main(int /* argc */, char* /* argv */[])
{
	vtkNew<vtkNamedColors> colors;

	// Create the contour widget
	vtkNew<vtkContourWidget> contourWidget;

	// Override the default representation for the contour widget to customize its
	// look
	vtkNew<vtkOrientedGlyphContourRepresentation> contourRepresentation;
	contourRepresentation->GetLinesProperty()->SetColor(
		colors->GetColor3d("Red").GetData());
	contourWidget->SetRepresentation(contourRepresentation);

	// Generate a set of points arranged in a circle
	int numPts = 10;
	vtkNew<vtkPoints> points;
	for (int i = 0; i < numPts; i++)
	{
		// Create numPts points evenly spread around a circumference of radius 0.1
		const double angle = 2.0 * vtkMath::Pi() * i / numPts;
		points->InsertPoint(static_cast<vtkIdType>(i), 0.1 * cos(angle),
			0.1 * sin(angle), 0.0);
	}

	// Create a cell array to connect the points into meaningful geometry
	vtkIdType* vertexIndices = new vtkIdType[numPts + 1];
	for (int i = 0; i < numPts; i++)
	{
		vertexIndices[i] = static_cast<vtkIdType>(i);
	}
	// Set the last vertex to 0; this means the last line segment will join the
	// 19th point (vertices[19]) with the first one (vertices[0]), thus closing
	// the circle.
	vertexIndices[numPts] = 0;
	vtkNew<vtkCellArray> lines;
	lines->InsertNextCell(numPts + 1, vertexIndices);

	// Create polydata to hold the geometry just created, and populate it
	vtkNew<vtkPolyData> polydata;
	polydata->SetPoints(points);
	polydata->SetLines(lines);

	// Create the renderer to visualize the scene
	vtkNew<vtkRenderer> renderer;
	renderer->SetBackground(colors->GetColor3d("MidnightBlue").GetData());

	// Create the GUI window to hold the rendered scene
	vtkNew<vtkRenderWindow> renderWindow;
	renderWindow->AddRenderer(renderer);
	renderWindow->SetWindowName("ContourWidget");
	renderWindow->SetSize(600, 600);

	// Create the events manager for the renderer window
	vtkNew<vtkRenderWindowInteractor> interactor;
	interactor->SetRenderWindow(renderWindow);

	// Use the "trackball camera" interactor style, rather than the default
	// "joystick camera"
	vtkNew<vtkInteractorStyleTrackballCamera> style;
	interactor->SetInteractorStyle(style);

	// Set up the contour widget within the visualization pipeline just assembled
	contourWidget->SetInteractor(interactor);
	contourWidget->On(); // Turn on the interactor observer
	contourWidget->Initialize(polydata);
	renderer->ResetCamera(); // Reposition camera to fit the scene elements

	// Start the interaction
	renderWindow->Render();
	interactor->Start();

	return EXIT_SUCCESS;
}