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