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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glPixelZoom">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glPixelZoom</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glPixelZoom</refname>
<refpurpose>specify the pixel zoom factors</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glPixelZoom</function></funcdef>
<paramdef>GLfloat <parameter>xfactor</parameter></paramdef>
<paramdef>GLfloat <parameter>yfactor</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>xfactor</parameter></term>
<term><parameter>yfactor</parameter></term>
<listitem>
<para>
Specify the
<inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
and
<inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
zoom factors for pixel write operations.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glPixelZoom</function> specifies values for the
<inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
and
<inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
zoom factors.
During the execution of <citerefentry><refentrytitle>glDrawPixels</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry>,
if
(<inlineequation><mml:math>
<!-- eqn: xr:-->
<mml:mi mathvariant="italic">xr</mml:mi>
</mml:math></inlineequation>,
<inlineequation><mml:math>
<!-- eqn: yr:-->
<mml:mi mathvariant="italic">yr</mml:mi>
</mml:math></inlineequation>)
is the current raster position,
and a given element is in the
<inlineequation><mml:math><mml:mi mathvariant="italic">m</mml:mi></mml:math></inlineequation>th
row and
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
column of the pixel rectangle,
then pixels whose centers are in the rectangle with corners at
</para>
<para>
(<inlineequation><mml:math>
<!-- eqn: xr + n cdot xfactor:-->
<mml:mrow>
<mml:mi mathvariant="italic">xr</mml:mi>
<mml:mo>+</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">n</mml:mi>
<mml:mo>·</mml:mo>
<mml:mi mathvariant="italic">xfactor</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></inlineequation>,
<inlineequation><mml:math>
<!-- eqn: yr + m cdot yfactor:-->
<mml:mrow>
<mml:mi mathvariant="italic">yr</mml:mi>
<mml:mo>+</mml:mo>
<mml:mrow>
<mml:mi mathvariant="italic">m</mml:mi>
<mml:mo>·</mml:mo>
<mml:mi mathvariant="italic">yfactor</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></inlineequation>)
</para>
<para>
(<inlineequation><mml:math>
<!-- eqn: xr + (n+1) cdot xfactor:-->
<mml:mrow>
<mml:mi mathvariant="italic">xr</mml:mi>
<mml:mo>+</mml:mo>
<mml:mrow>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:mi mathvariant="italic">n</mml:mi>
<mml:mo>+</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:mfenced>
<mml:mo>·</mml:mo>
<mml:mi mathvariant="italic">xfactor</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></inlineequation>,
<inlineequation><mml:math>
<!-- eqn: yr + (m+1) cdot yfactor:-->
<mml:mrow>
<mml:mi mathvariant="italic">yr</mml:mi>
<mml:mo>+</mml:mo>
<mml:mrow>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:mi mathvariant="italic">m</mml:mi>
<mml:mo>+</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:mfenced>
<mml:mo>·</mml:mo>
<mml:mi mathvariant="italic">yfactor</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></inlineequation>)
</para>
<para>
are candidates for replacement.
Any pixel whose center lies on the bottom or left edge of this rectangular
region is also modified.
</para>
<para>
Pixel zoom factors are not limited to positive values.
Negative zoom factors reflect the resulting image about the current
raster position.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glPixelZoom</function>
is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_ZOOM_X</constant>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_ZOOM_Y</constant>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glDrawPixels</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>