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119 lines
2.9 KiB
ReStructuredText
119 lines
2.9 KiB
ReStructuredText
.. _launching_viz:
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Launching Viz
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*************
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Goal
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====
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In this tutorial you will learn how to
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.. container:: enumeratevisibleitemswithsquare
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* Open a visualization window.
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* Access a window by its name.
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* Start event loop.
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* Start event loop for a given amount of time.
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Code
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====
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You can download the code from :download:`here <../../../../samples/cpp/tutorial_code/viz/launching_viz.cpp>`.
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.. code-block:: cpp
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#include <opencv2/viz.hpp>
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#include <iostream>
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using namespace cv;
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using namespace std;
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/**
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* @function main
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*/
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int main()
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{
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/// Create a window
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viz::Viz3d myWindow("Viz Demo");
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/// Start event loop
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myWindow.spin();
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/// Event loop is over when pressed q, Q, e, E
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cout << "First event loop is over" << endl;
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/// Access window via its name
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viz::Viz3d sameWindow = viz::getWindowByName("Viz Demo");
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/// Start event loop
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sameWindow.spin();
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/// Event loop is over when pressed q, Q, e, E
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cout << "Second event loop is over" << endl;
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/// Event loop is over when pressed q, Q, e, E
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/// Start event loop once for 1 millisecond
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sameWindow.spinOnce(1, true);
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while(!sameWindow.wasStopped())
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{
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/// Interact with window
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/// Event loop for 1 millisecond
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sameWindow.spinOnce(1, true);
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}
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/// Once more event loop is stopped
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cout << "Last event loop is over" << endl;
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return 0;
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}
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Explanation
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===========
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Here is the general structure of the program:
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* Create a window.
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.. code-block:: cpp
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/// Create a window
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viz::Viz3d myWindow("Viz Demo");
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* Start event loop. This event loop will run until user terminates it by pressing **e**, **E**, **q**, **Q**.
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.. code-block:: cpp
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/// Start event loop
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myWindow.spin();
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* Access same window via its name. Since windows are implicitly shared, **sameWindow** is exactly the same with **myWindow**. If the name does not exist, a new window is created.
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.. code-block:: cpp
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/// Access window via its name
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viz::Viz3d sameWindow = viz::get("Viz Demo");
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* Start a controlled event loop. Once it starts, **wasStopped** is set to false. Inside the while loop, in each iteration, **spinOnce** is called to prevent event loop from completely stopping. Inside the while loop, user can execute other statements including those which interact with the window.
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.. code-block:: cpp
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/// Event loop is over when pressed q, Q, e, E
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/// Start event loop once for 1 millisecond
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sameWindow.spinOnce(1, true);
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while(!sameWindow.wasStopped())
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{
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/// Interact with window
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/// Event loop for 1 millisecond
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sameWindow.spinOnce(1, true);
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}
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Results
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=======
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Here is the result of the program.
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.. image:: images/window_demo.png
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:alt: Launching Viz
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:align: center
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