
<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>&CenterDot;</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>&CenterDot;</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>&CenterDot;</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>&CenterDot;</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>
