<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qmlspectrogram.qdoc --> <title>Qt Quick 2 Spectrogram Example | Qt Data Visualization 5.9</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.9</td><td ><a href="qtdatavisualization-index.html">Qt Data Visualization</a></td><td >Qt Quick 2 Spectrogram Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#running-the-example">Running the Example</a></li> <li class="level1"><a href="#creating-a-spectrogram">Creating a Spectrogram</a></li> <li class="level1"><a href="#polar-spectrogram">Polar Spectrogram</a></li> <li class="level1"><a href="#example-contents">Example Contents</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Qt Quick 2 Spectrogram Example</h1> <span class="subtitle"></span> <!-- $$$qmlspectrogram-description --> <div class="descr"> <a name="details"></a> <p>The Qt Quick 2 Spectrogram example demonstrates how to show a polar and cartesian spectrograms and how to utilize orthographic projection to show them in 2D.</p> <p class="centerAlign"><img src="images/qmlspectrogram-example.png" alt="" /></p><p>Spectrogram is simply a surface graph with a range gradient used to emphasize the different values. Typically spectrograms are shown with two dimensional surfaces, which we simulate with a top down orthographic view of the graph. To enforce the 2D effect, we disable the graph rotation via mouse or touch when in the orthographic mode.</p> <p>The focus in this example is on showing how to display spectrograms, so the basic functionality is not explained. For more detailed QML example documentation, see <a href="qtdatavisualization-qmlscatter-example.html">Qt Quick 2 Scatter Example</a>.</p> <a name="running-the-example"></a> <h2 id="running-the-example">Running the Example</h2> <p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p> <a name="creating-a-spectrogram"></a> <h2 id="creating-a-spectrogram">Creating a Spectrogram</h2> <p>To create a 2D spectrogram, we define a <a href="qml-qtdatavisualization-surface3d.html">Surface3D</a> item:</p> <pre class="qml"> <span class="type"><a href="qml-qtdatavisualization-surface3d.html">Surface3D</a></span> { <span class="name">id</span>: <span class="name">surfaceGraph</span> <span class="name">width</span>: <span class="name">surfaceView</span>.<span class="name">width</span> <span class="name">height</span>: <span class="name">surfaceView</span>.<span class="name">height</span> <span class="name">shadowQuality</span>: <span class="name">AbstractGraph3D</span>.<span class="name">ShadowQualityNone</span> <span class="name">selectionMode</span>: <span class="name">AbstractGraph3D</span>.<span class="name">SelectionSlice</span> <span class="operator">|</span> <span class="name">AbstractGraph3D</span>.<span class="name">SelectionItemAndColumn</span> <span class="name">axisX</span>: <span class="name">xAxis</span> <span class="name">axisY</span>: <span class="name">yAxis</span> <span class="name">axisZ</span>: <span class="name">zAxis</span> <span class="name">theme</span>: <span class="name">customTheme</span> <span class="name">inputHandler</span>: <span class="name">customInputHandler</span> <span class="comment">// Remove the perspective and view the graph from top down to achieve 2D effect</span> <span class="name">orthoProjection</span>: <span class="number">true</span> <span class="name">scene</span>.activeCamera.cameraPreset: <span class="name">Camera3D</span>.<span class="name">CameraPresetDirectlyAbove</span> <span class="name">flipHorizontalGrid</span>: <span class="number">true</span> <span class="name">radialLabelOffset</span>: <span class="number">0.01</span> <span class="name">horizontalAspectRatio</span>: <span class="number">1</span> <span class="name">scene</span>.activeCamera.zoomLevel: <span class="number">85</span> <span class="type"><a href="qml-qtdatavisualization-surface3dseries.html">Surface3DSeries</a></span> { <span class="name">id</span>: <span class="name">surfaceSeries</span> <span class="name">flatShadingEnabled</span>: <span class="number">false</span> <span class="name">drawMode</span>: <span class="name">Surface3DSeries</span>.<span class="name">DrawSurface</span> <span class="name">baseGradient</span>: <span class="name">surfaceGradient</span> <span class="name">colorStyle</span>: <span class="name">Theme3D</span>.<span class="name">ColorStyleRangeGradient</span> <span class="name">itemLabelFormat</span>: <span class="string">"(@xLabel, @zLabel): @yLabel"</span> <span class="type"><a href="qml-qtdatavisualization-itemmodelsurfacedataproxy.html">ItemModelSurfaceDataProxy</a></span> { <span class="name">itemModel</span>: <span class="name">surfaceData</span>.<span class="name">model</span> <span class="name">rowRole</span>: <span class="string">"radius"</span> <span class="name">columnRole</span>: <span class="string">"angle"</span> <span class="name">yPosRole</span>: <span class="string">"value"</span> } } } </pre> <p>The key properties for enabling the 2D effect are <a href="qml-qtdatavisualization-abstractgraph3d.html#orthoProjection-prop">orthoProjection</a> and <a href="qml-qtdatavisualization-camera3d.html#cameraPreset-prop">scene.activeCamera.cameraPreset</a>. We remove the perspective by enabling orthographic projection for the graph, and then we eliminate the Y-dimension by viewing the graph directly from above:</p> <pre class="qml"> <span class="name">orthoProjection</span>: <span class="number">true</span> <span class="name">scene</span>.activeCamera.cameraPreset: <span class="name">Camera3D</span>.<span class="name">CameraPresetDirectlyAbove</span> </pre> <p>Since this viewpoint causes the horizontal axis grid to be mostly obscured by the surface, we also specify that the horizontal grid should be drawn on top of the graph:</p> <pre class="qml"> <span class="name">flipHorizontalGrid</span>: <span class="number">true</span> </pre> <a name="polar-spectrogram"></a> <h2 id="polar-spectrogram">Polar Spectrogram</h2> <p>Depending on the data, it is sometimes more natural to use a polar graph instead of a cartesian one. Qt Data Visualization supports this via <a href="qml-qtdatavisualization-abstractgraph3d.html#polar-prop">polar</a> property. In this example we provide a button to switch between polar and cartesian modes:</p> <pre class="qml"> <span class="type">NewButton</span> { <span class="name">id</span>: <span class="name">polarToggle</span> <span class="name">Layout</span>.fillWidth: <span class="number">true</span> <span class="name">Layout</span>.fillHeight: <span class="number">true</span> <span class="name">text</span>: <span class="string">"Switch to polar"</span> <span class="name">onClicked</span>: { <span class="keyword">if</span> (<span class="name">surfaceGraph</span>.<span class="name">polar</span> <span class="operator">===</span> <span class="number">false</span>) { <span class="name">surfaceGraph</span>.<span class="name">polar</span> <span class="operator">=</span> <span class="number">true</span> <span class="name">text</span> <span class="operator">=</span> <span class="string">"Switch to cartesian"</span> } <span class="keyword">else</span> { <span class="name">surfaceGraph</span>.<span class="name">polar</span> <span class="operator">=</span> <span class="number">false</span> <span class="name">text</span> <span class="operator">=</span> <span class="string">"Switch to polar"</span> } } } </pre> <p>In the polar mode, the X-axis is converted into the angular polar axis, and the Z-axis is converted into the radial polar axis. The surface points are recalculated according to new axes.</p> <p>The radial axis labels are drawn outside the graph by default, but in this example we want to draw them right next to the 0 degree angular axis inside the graph, so we define only a tiny offset for them:</p> <pre class="qml"> <span class="name">radialLabelOffset</span>: <span class="number">0.01</span> </pre> <p>To enforce the 2D effect, graph rotation via user input is disabled when in orthographic mode. We do this by specifying a new input handler:</p> <pre class="qml"> <span class="type"><a href="qml-qtdatavisualization-touchinputhandler3d.html">TouchInputHandler3D</a></span> { <span class="name">id</span>: <span class="name">customInputHandler</span> <span class="name">rotationEnabled</span>: <span class="number">false</span> } <span class="type"><a href="qml-qtdatavisualization-surface3d.html">Surface3D</a></span> { ... <span class="name">inputHandler</span>: <span class="name">customInputHandler</span> ... </pre> <p>When the projection mode changes, we adjust the value of the <a href="qml-qtdatavisualization-inputhandler3d.html#rotationEnabled-prop">rotationEnabled</a> property of the <code>customInputHandler</code> to control the rotation.</p> <a name="example-contents"></a> <h2 id="example-contents">Example Contents</h2> <p>Files:</p> <ul> <li><a href="qtdatavisualization-qmlspectrogram-qml-qmlspectrogram-data-qml.html">qmlspectrogram/qml/qmlspectrogram/Data.qml</a></li> <li><a href="qtdatavisualization-qmlspectrogram-qml-qmlspectrogram-newbutton-qml.html">qmlspectrogram/qml/qmlspectrogram/NewButton.qml</a></li> <li><a href="qtdatavisualization-qmlspectrogram-qml-qmlspectrogram-main-qml.html">qmlspectrogram/qml/qmlspectrogram/main.qml</a></li> <li><a href="qtdatavisualization-qmlspectrogram-main-cpp.html">qmlspectrogram/main.cpp</a></li> <li><a href="qtdatavisualization-qmlspectrogram-qmlspectrogram-pro.html">qmlspectrogram/qmlspectrogram.pro</a></li> <li><a href="qtdatavisualization-qmlspectrogram-qmlspectrogram-qrc.html">qmlspectrogram/qmlspectrogram.qrc</a></li> </ul> </div> <!-- @@@qmlspectrogram --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2017 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>