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<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
<!ENTITY version SYSTEM "version.xml">
]>
<refentry id="cairo-Transformations">
<refmeta>
<refentrytitle role="top_of_page">Transformations</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>CAIRO Library</refmiscinfo>
</refmeta>
<refnamediv>
<refname>Transformations</refname>
<refpurpose>Manipulating the current transformation matrix</refpurpose>
<!--[<xref linkend="desc" endterm="desc.title"/>]-->
</refnamediv>
<refsynopsisdiv role="synopsis">
<title role="synopsis.title">Synopsis</title>
<synopsis>
<link linkend="void">void</link> <link linkend="cairo-translate">cairo_translate</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> tx,
<link linkend="double">double</link> ty);
<link linkend="void">void</link> <link linkend="cairo-scale">cairo_scale</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> sx,
<link linkend="double">double</link> sy);
<link linkend="void">void</link> <link linkend="cairo-rotate">cairo_rotate</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> angle);
<link linkend="void">void</link> <link linkend="cairo-transform">cairo_transform</link> (<link linkend="cairo-t">cairo_t</link> *cr,
const <link linkend="cairo-matrix-t">cairo_matrix_t</link> *matrix);
<link linkend="void">void</link> <link linkend="cairo-set-matrix">cairo_set_matrix</link> (<link linkend="cairo-t">cairo_t</link> *cr,
const <link linkend="cairo-matrix-t">cairo_matrix_t</link> *matrix);
<link linkend="void">void</link> <link linkend="cairo-get-matrix">cairo_get_matrix</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="cairo-matrix-t">cairo_matrix_t</link> *matrix);
<link linkend="void">void</link> <link linkend="cairo-identity-matrix">cairo_identity_matrix</link> (<link linkend="cairo-t">cairo_t</link> *cr);
<link linkend="void">void</link> <link linkend="cairo-user-to-device">cairo_user_to_device</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *x,
<link linkend="double">double</link> *y);
<link linkend="void">void</link> <link linkend="cairo-user-to-device-distance">cairo_user_to_device_distance</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *dx,
<link linkend="double">double</link> *dy);
<link linkend="void">void</link> <link linkend="cairo-device-to-user">cairo_device_to_user</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *x,
<link linkend="double">double</link> *y);
<link linkend="void">void</link> <link linkend="cairo-device-to-user-distance">cairo_device_to_user_distance</link> (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *dx,
<link linkend="double">double</link> *dy);
</synopsis>
</refsynopsisdiv>
<refsect1 role="desc">
<title role="desc.title">Description</title>
<para>
</para>
</refsect1>
<refsect1 role="details">
<title role="details.title">Details</title>
<refsect2>
<title><anchor id="cairo-translate" role="function"/>cairo_translate ()</title>
<indexterm><primary>cairo_translate</primary></indexterm><programlisting><link linkend="void">void</link> cairo_translate (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> tx,
<link linkend="double">double</link> ty);</programlisting>
<para>
Modifies the current transformation matrix (CTM) by translating the
user-space origin by (<parameter>tx</parameter>, <parameter>ty</parameter>). 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.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>tx</parameter> :</term>
<listitem><simpara> amount to translate in the X direction
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>ty</parameter> :</term>
<listitem><simpara> amount to translate in the Y direction
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-scale" role="function"/>cairo_scale ()</title>
<indexterm><primary>cairo_scale</primary></indexterm><programlisting><link linkend="void">void</link> cairo_scale (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> sx,
<link linkend="double">double</link> sy);</programlisting>
<para>
Modifies the current transformation matrix (CTM) by scaling the X
and Y user-space axes by <parameter>sx</parameter> and <parameter>sy</parameter> respectively. The scaling of
the axes takes place after any existing transformation of user
space.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>sx</parameter> :</term>
<listitem><simpara> scale factor for the X dimension
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>sy</parameter> :</term>
<listitem><simpara> scale factor for the Y dimension
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-rotate" role="function"/>cairo_rotate ()</title>
<indexterm><primary>cairo_rotate</primary></indexterm><programlisting><link linkend="void">void</link> cairo_rotate (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> angle);</programlisting>
<para>
Modifies the current transformation matrix (CTM) by rotating the
user-space axes by <parameter>angle</parameter> 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.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>angle</parameter> :</term>
<listitem><simpara> angle (in radians) by which the user-space axes will be
rotated
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-transform" role="function"/>cairo_transform ()</title>
<indexterm><primary>cairo_transform</primary></indexterm><programlisting><link linkend="void">void</link> cairo_transform (<link linkend="cairo-t">cairo_t</link> *cr,
const <link linkend="cairo-matrix-t">cairo_matrix_t</link> *matrix);</programlisting>
<para>
Modifies the current transformation matrix (CTM) by applying
<parameter>matrix</parameter> as an additional transformation. The new transformation of
user space takes place after any existing transformation.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>matrix</parameter> :</term>
<listitem><simpara> a transformation to be applied to the user-space axes
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-set-matrix" role="function"/>cairo_set_matrix ()</title>
<indexterm><primary>cairo_set_matrix</primary></indexterm><programlisting><link linkend="void">void</link> cairo_set_matrix (<link linkend="cairo-t">cairo_t</link> *cr,
const <link linkend="cairo-matrix-t">cairo_matrix_t</link> *matrix);</programlisting>
<para>
Modifies the current transformation matrix (CTM) by setting it
equal to <parameter>matrix</parameter>.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>matrix</parameter> :</term>
<listitem><simpara> a transformation matrix from user space to device space
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-get-matrix" role="function"/>cairo_get_matrix ()</title>
<indexterm><primary>cairo_get_matrix</primary></indexterm><programlisting><link linkend="void">void</link> cairo_get_matrix (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="cairo-matrix-t">cairo_matrix_t</link> *matrix);</programlisting>
<para>
Stores the current transformation matrix (CTM) into <parameter>matrix</parameter>.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>matrix</parameter> :</term>
<listitem><simpara> return value for the matrix
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-identity-matrix" role="function"/>cairo_identity_matrix ()</title>
<indexterm><primary>cairo_identity_matrix</primary></indexterm><programlisting><link linkend="void">void</link> cairo_identity_matrix (<link linkend="cairo-t">cairo_t</link> *cr);</programlisting>
<para>
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.</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-user-to-device" role="function"/>cairo_user_to_device ()</title>
<indexterm><primary>cairo_user_to_device</primary></indexterm><programlisting><link linkend="void">void</link> cairo_user_to_device (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *x,
<link linkend="double">double</link> *y);</programlisting>
<para>
Transform a coordinate from user space to device space by
multiplying the given point by the current transformation matrix
(CTM).</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>x</parameter> :</term>
<listitem><simpara> X value of coordinate (in/out parameter)
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>y</parameter> :</term>
<listitem><simpara> Y value of coordinate (in/out parameter)
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-user-to-device-distance" role="function"/>cairo_user_to_device_distance ()</title>
<indexterm><primary>cairo_user_to_device_distance</primary></indexterm><programlisting><link linkend="void">void</link> cairo_user_to_device_distance (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *dx,
<link linkend="double">double</link> *dy);</programlisting>
<para>
Transform a distance vector from user space to device space. This
function is similar to <link linkend="cairo-user-to-device"><function>cairo_user_to_device()</function></link> except that the
translation components of the CTM will be ignored when transforming
(<parameter>dx</parameter>,<parameter>dy</parameter>).</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>dx</parameter> :</term>
<listitem><simpara> X component of a distance vector (in/out parameter)
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>dy</parameter> :</term>
<listitem><simpara> Y component of a distance vector (in/out parameter)
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-device-to-user" role="function"/>cairo_device_to_user ()</title>
<indexterm><primary>cairo_device_to_user</primary></indexterm><programlisting><link linkend="void">void</link> cairo_device_to_user (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *x,
<link linkend="double">double</link> *y);</programlisting>
<para>
Transform a coordinate from device space to user space by
multiplying the given point by the inverse of the current
transformation matrix (CTM).</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>x</parameter> :</term>
<listitem><simpara> X value of coordinate (in/out parameter)
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>y</parameter> :</term>
<listitem><simpara> Y value of coordinate (in/out parameter)
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="cairo-device-to-user-distance" role="function"/>cairo_device_to_user_distance ()</title>
<indexterm><primary>cairo_device_to_user_distance</primary></indexterm><programlisting><link linkend="void">void</link> cairo_device_to_user_distance (<link linkend="cairo-t">cairo_t</link> *cr,
<link linkend="double">double</link> *dx,
<link linkend="double">double</link> *dy);</programlisting>
<para>
Transform a distance vector from device space to user space. This
function is similar to <link linkend="cairo-device-to-user"><function>cairo_device_to_user()</function></link> except that the
translation components of the inverse CTM will be ignored when
transforming (<parameter>dx</parameter>,<parameter>dy</parameter>).</para>
<para>
</para><variablelist role="params">
<varlistentry><term><parameter>cr</parameter> :</term>
<listitem><simpara> a cairo context
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>dx</parameter> :</term>
<listitem><simpara> X component of a distance vector (in/out parameter)
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>dy</parameter> :</term>
<listitem><simpara> Y component of a distance vector (in/out parameter)
</simpara></listitem></varlistentry>
</variablelist></refsect2>
</refsect1>
</refentry>
|
