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<title>libQGLViewer textureViewer example</title>
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<h1>The textureViewer example</h1>
<center>
<img src="../images/textureViewer.jpg" width="300" height="200" alt="textureViewer"/>
</center>
<p>
Loads image files and textures map polygons with it.
</p>
<p>
Pedagogical example that shows how to apply a texture on a 3D object.
Inpired from the Qt texture example.
</p>
<p>
The Qt QImage class and its <code>convertToGLFormat()</code> function are used
to load any image format. The image is resized so that its dimensions are powers
of two if needed. Feel free to cut and paste.
</p>
<h2>textureViewer.h</h2>
<pre>
<span class="dir">#include <QGLViewer/qglviewer.h>
</span>
<span class="key">class </span>Viewer : <span class="key">public </span>QGLViewer
{
<span class="key">protected </span>:
<span class="key">virtual </span><span class="typ">void </span>init();
<span class="key">virtual </span><span class="typ">void </span>draw();
<span class="key">virtual </span><span class="typ">void </span>keyPressEvent(QKeyEvent *e);
<span class="key">virtual </span>QString helpString() <span class="typ">const</span>;
<span class="typ">void </span>loadImage();
<span class="key">private </span>:
<span class="typ">float </span>ratio, u_max, v_max;
};</pre>
<h2>textureViewer.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"textureViewer.h"</span><span class="dir">
</span>
<span class="dir">#include <qimage.h>
</span><span class="dir">#include <qfiledialog.h>
</span>
<span class="key">using namespace </span>qglviewer;
<span class="key">using namespace </span>std;
<span class="typ">void </span>Viewer::init()
{
restoreFromFile();
<span class="com">// Enable GL textures
</span> glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glEnable( GL_TEXTURE_2D );
<span class="com">// Nice texture coordinate interpolation
</span> glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );
u_max = <span class="num">1.0</span>;
v_max = <span class="num">1.0</span>;
ratio = <span class="num">1.0</span>;
loadImage();
help();
}
<span class="typ">void </span>Viewer::draw()
{
<span class="com">// Display the quad
</span> glNormal3f(<span class="num">0.0</span>, <span class="num">0.0</span>, <span class="num">1.0</span>);
glBegin(GL_QUADS);
glTexCoord2f(<span class="num">0.0</span>, <span class="num">1.0</span>-v_max); glVertex2f(-u_max*ratio,-v_max);
glTexCoord2f(<span class="num">0.0</span>, <span class="num">1.0</span>); glVertex2f(-u_max*ratio, v_max);
glTexCoord2f(u_max, <span class="num">1.0</span>); glVertex2f( u_max*ratio, v_max);
glTexCoord2f(u_max, <span class="num">1.0</span>-v_max); glVertex2f( u_max*ratio,-v_max);
glEnd();
}
<span class="typ">void </span>Viewer::loadImage()
{
QString name = QFileDialog::getOpenFileName(<span class="str">"."</span>, <span class="str">"Images (*.png *.xpm *.jpg)"</span>, <span class="key">this</span>, <span class="str">"Choose"</span>, <span class="str">"Select an image"</span>);
<span class="com">// In case of Cancel
</span> <span class="key">if </span>(name.isEmpty())
<span class="key">return</span>;
QImage img(name);
<span class="key">if </span>(img.isNull())
{
cerr << <span class="str">"Unable to load "</span> << name << <span class="str">", unsupported file format"</span> << endl;
<span class="key">return</span>;
}
cout << <span class="str">"Loading "</span> << name << <span class="str">", "</span> << img.width() << <span class="str">"x"</span> << img.height() << <span class="str">" pixels"</span> << endl;
<span class="com">// 1E-3 needed. Just try with width=128 and see !
</span> <span class="typ">int </span>newWidth = <span class="num">1</span><<(<span class="typ">int</span>)(<span class="num">1</span>+log(img.width() <span class="num">-1</span>+<span class="num">1</span>E-3) / log(<span class="num">2.0</span>));
<span class="typ">int </span>newHeight = <span class="num">1</span><<(<span class="typ">int</span>)(<span class="num">1</span>+log(img.height()<span class="num">-1</span>+<span class="num">1</span>E-3) / log(<span class="num">2.0</span>));
u_max = img.width() / (<span class="typ">float</span>)newWidth;
v_max = img.height() / (<span class="typ">float</span>)newHeight;
<span class="key">if </span>((img.width()!=newWidth) || (img.height()!=newHeight))
{
cout << <span class="str">"Image size set to "</span> << newWidth << <span class="str">"x"</span> << newHeight << <span class="str">" pixels"</span> << endl;
img = img.copy(<span class="num">0</span>, <span class="num">0</span>, newWidth, newHeight);
}
ratio = newWidth / (<span class="typ">float</span>)newHeight;
QImage glImg = QGLWidget::convertToGLFormat(img); <span class="com">// flipped 32bit RGBA
</span>
<span class="com">// Bind the img texture...
</span> glTexImage2D(GL_TEXTURE_2D, <span class="num">0</span>, <span class="num">4</span>, glImg.width(), glImg.height(), <span class="num">0</span>,
GL_RGBA, GL_UNSIGNED_BYTE, glImg.bits());
}
<span class="typ">void </span>Viewer::keyPressEvent(QKeyEvent *e)
{
<span class="key">switch </span>(e->key())
{
<span class="key">case </span>Qt::Key_L : loadImage(); <span class="key">break</span>;
<span class="key">default</span>: QGLViewer::keyPressEvent(e);
}
}
QString Viewer::helpString() <span class="typ">const
</span>{
QString text(<span class="str">"<h2>T e x t u r e V i e w e r</h2>"</span>);
text += <span class="str">"This pedagogical example illustrates how to texture map a polygon.<br>"</span>;
text += <span class="str">"The Qt <i>QImage</i> class and its <i>convertToGLFormat()</i> function are used "</span>;
text += <span class="str">"to load an image in any format. The image is resized so that its dimensions "</span>;
text += <span class="str">"are powers of two if needed. Feel free to cut and paste.<br>"</span>;
text += <span class="str">"Press <b>L</b>(oad) to load a new image."</span>;
<span class="key">return </span>text;
}</pre>
<h2>main.cpp</h2>
<pre>
<span class="dir">#include </span><span class="dstr">"textureViewer.h"</span><span class="dir">
</span><span class="dir">#include <qapplication.h>
</span>
<span class="typ">int </span>main(<span class="typ">int </span>argc, <span class="typ">char</span>** argv)
{
<span class="com">// Read command lines arguments.
</span> QApplication application(argc,argv);
<span class="com">// Instantiate the viewer, show it on screen.
</span> Viewer viewer;
viewer.show();
<span class="com">// Set the viewer as the application main widget.
</span> application.setMainWidget(&viewer);
<span class="com">// Run main loop.
</span> <span class="key">return </span>application.exec();
}</pre>
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<i>Last modified on Thursday, February 5, 2004.</i>
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