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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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 | 
<a href="#id2532835" class="shortcut">Description</a></nobr></td></tr>
</table>
<div class="refentry" lang="en">
<a name="cairo-Transformations"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2>
<a name="id2547030"></a><span class="refentrytitle">Transformations</span>
</h2>
<p>Transformations — Manipulating the current transformation matrix</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<pre class="synopsis">
void <a href="cairo-Transformations.html#cairo-translate">cairo_translate</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double tx,
double ty);
void <a href="cairo-Transformations.html#cairo-scale">cairo_scale</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double sx,
double sy);
void <a href="cairo-Transformations.html#cairo-rotate">cairo_rotate</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double angle);
void <a href="cairo-Transformations.html#cairo-transform">cairo_transform</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
const <a href="cairo-cairo-matrix-t.html#cairo-matrix-t">cairo_matrix_t</a> *matrix);
void <a href="cairo-Transformations.html#cairo-set-matrix">cairo_set_matrix</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
const <a href="cairo-cairo-matrix-t.html#cairo-matrix-t">cairo_matrix_t</a> *matrix);
void <a href="cairo-Transformations.html#cairo-get-matrix">cairo_get_matrix</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
<a href="cairo-cairo-matrix-t.html#cairo-matrix-t">cairo_matrix_t</a> *matrix);
void <a href="cairo-Transformations.html#cairo-identity-matrix">cairo_identity_matrix</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr);
void <a href="cairo-Transformations.html#cairo-user-to-device">cairo_user_to_device</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *x,
double *y);
void <a href="cairo-Transformations.html#cairo-user-to-device-distance">cairo_user_to_device_distance</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *dx,
double *dy);
void <a href="cairo-Transformations.html#cairo-device-to-user">cairo_device_to_user</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *x,
double *y);
void <a href="cairo-Transformations.html#cairo-device-to-user-distance">cairo_device_to_user_distance</a> (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *dx,
double *dy);
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id2532835"></a><h2>Description</h2>
<p>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2532851"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="id2532862"></a><h3>
<a name="cairo-translate"></a>cairo_translate ()</h3>
<a class="indexterm" name="id2532874"></a><pre class="programlisting">void cairo_translate (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double tx,
double ty);</pre>
<p>
Modifies the current transformation matrix (CTM) by translating the
user-space origin by (<em class="parameter"><code>tx</code></em>, <em class="parameter"><code>ty</code></em>). This offset is interpreted as a
user-space coordinate according to the CTM in place before the new
call to cairo_translate. In other words, the translation of the
user-space origin takes place after any existing transformation.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>tx</code></em> :</span></td>
<td> amount to translate in the X direction
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>ty</code></em> :</span></td>
<td> amount to translate in the Y direction
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2575529"></a><h3>
<a name="cairo-scale"></a>cairo_scale ()</h3>
<a class="indexterm" name="id2575541"></a><pre class="programlisting">void cairo_scale (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double sx,
double sy);</pre>
<p>
Modifies the current transformation matrix (CTM) by scaling the X
and Y user-space axes by <em class="parameter"><code>sx</code></em> and <em class="parameter"><code>sy</code></em> respectively. The scaling of
the axes takes place after any existing transformation of user
space.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>sx</code></em> :</span></td>
<td> scale factor for the X dimension
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>sy</code></em> :</span></td>
<td> scale factor for the Y dimension
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2575646"></a><h3>
<a name="cairo-rotate"></a>cairo_rotate ()</h3>
<a class="indexterm" name="id2575658"></a><pre class="programlisting">void cairo_rotate (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double angle);</pre>
<p>
Modifies the current transformation matrix (CTM) by rotating the
user-space axes by <em class="parameter"><code>angle</code></em> radians. The rotation of the axes takes
places after any existing transformation of user space. The
rotation direction for positive angles is from the positive X axis
toward the positive Y axis.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>angle</code></em> :</span></td>
<td> angle (in radians) by which the user-space axes will be
rotated
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2574418"></a><h3>
<a name="cairo-transform"></a>cairo_transform ()</h3>
<a class="indexterm" name="id2574430"></a><pre class="programlisting">void cairo_transform (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
const <a href="cairo-cairo-matrix-t.html#cairo-matrix-t">cairo_matrix_t</a> *matrix);</pre>
<p>
Modifies the current transformation matrix (CTM) by applying
<em class="parameter"><code>matrix</code></em> as an additional transformation. The new transformation of
user space takes place after any existing transformation.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>matrix</code></em> :</span></td>
<td> a transformation to be applied to the user-space axes
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2574511"></a><h3>
<a name="cairo-set-matrix"></a>cairo_set_matrix ()</h3>
<a class="indexterm" name="id2574523"></a><pre class="programlisting">void cairo_set_matrix (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
const <a href="cairo-cairo-matrix-t.html#cairo-matrix-t">cairo_matrix_t</a> *matrix);</pre>
<p>
Modifies the current transformation matrix (CTM) by setting it
equal to <em class="parameter"><code>matrix</code></em>.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>matrix</code></em> :</span></td>
<td> a transformation matrix from user space to device space
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2574602"></a><h3>
<a name="cairo-get-matrix"></a>cairo_get_matrix ()</h3>
<a class="indexterm" name="id2574614"></a><pre class="programlisting">void cairo_get_matrix (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
<a href="cairo-cairo-matrix-t.html#cairo-matrix-t">cairo_matrix_t</a> *matrix);</pre>
<p>
Stores the current transformation matrix (CTM) into <em class="parameter"><code>matrix</code></em>.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>matrix</code></em> :</span></td>
<td> return value for the matrix
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2527705"></a><h3>
<a name="cairo-identity-matrix"></a>cairo_identity_matrix ()</h3>
<a class="indexterm" name="id2527716"></a><pre class="programlisting">void cairo_identity_matrix (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr);</pre>
<p>
Resets the current transformation matrix (CTM) by setting it equal
to the identity matrix. That is, the user-space and device-space
axes will be aligned and one user-space unit will transform to one
device-space unit.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2527769"></a><h3>
<a name="cairo-user-to-device"></a>cairo_user_to_device ()</h3>
<a class="indexterm" name="id2527780"></a><pre class="programlisting">void cairo_user_to_device (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *x,
double *y);</pre>
<p>
Transform a coordinate from user space to device space by
multiplying the given point by the current transformation matrix
(CTM).</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x</code></em> :</span></td>
<td> X value of coordinate (in/out parameter)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y</code></em> :</span></td>
<td> Y value of coordinate (in/out parameter)
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2527874"></a><h3>
<a name="cairo-user-to-device-distance"></a>cairo_user_to_device_distance ()</h3>
<a class="indexterm" name="id2527886"></a><pre class="programlisting">void cairo_user_to_device_distance (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *dx,
double *dy);</pre>
<p>
Transform a distance vector from user space to device space. This
function is similar to <a href="cairo-Transformations.html#cairo-user-to-device"><code class="function">cairo_user_to_device()</code></a> except that the
translation components of the CTM will be ignored when transforming
(<em class="parameter"><code>dx</code></em>,<em class="parameter"><code>dy</code></em>).</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>dx</code></em> :</span></td>
<td> X component of a distance vector (in/out parameter)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>dy</code></em> :</span></td>
<td> Y component of a distance vector (in/out parameter)
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2528002"></a><h3>
<a name="cairo-device-to-user"></a>cairo_device_to_user ()</h3>
<a class="indexterm" name="id2528013"></a><pre class="programlisting">void cairo_device_to_user (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *x,
double *y);</pre>
<p>
Transform a coordinate from device space to user space by
multiplying the given point by the inverse of the current
transformation matrix (CTM).</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x</code></em> :</span></td>
<td> X value of coordinate (in/out parameter)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y</code></em> :</span></td>
<td> Y value of coordinate (in/out parameter)
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2528108"></a><h3>
<a name="cairo-device-to-user-distance"></a>cairo_device_to_user_distance ()</h3>
<a class="indexterm" name="id2528119"></a><pre class="programlisting">void cairo_device_to_user_distance (<a href="cairo-cairo-t.html#cairo-t">cairo_t</a> *cr,
double *dx,
double *dy);</pre>
<p>
Transform a distance vector from device space to user space. This
function is similar to <a href="cairo-Transformations.html#cairo-device-to-user"><code class="function">cairo_device_to_user()</code></a> except that the
translation components of the inverse CTM will be ignored when
transforming (<em class="parameter"><code>dx</code></em>,<em class="parameter"><code>dy</code></em>).</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>cr</code></em> :</span></td>
<td> a cairo context
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>dx</code></em> :</span></td>
<td> X component of a distance vector (in/out parameter)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>dy</code></em> :</span></td>
<td> Y component of a distance vector (in/out parameter)
</td>
</tr>
</tbody>
</table></div>
</div>
</div>
</div>
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