upstream-doc/man2/glMinmax.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glMinmax">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glMinmax</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glMinmax</refname>
  17         <refpurpose>define minmax table</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glMinmax</function></funcdef>
  23                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  24                 <paramdef>GLenum <parameter>internalformat</parameter></paramdef>
  25                 <paramdef>GLboolean <parameter>sink</parameter></paramdef>
  26             </funcprototype>
  27         </funcsynopsis>
  28     </refsynopsisdiv>
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>target</parameter></term>
  33             <listitem>
  34                 <para>
  35                     The minmax table whose parameters are to be set.
  36                     Must be
  37                     <constant>GL_MINMAX</constant>.
  38                 </para>
  39             </listitem>
  40         </varlistentry>
  41         <varlistentry>
  42             <term><parameter>internalformat</parameter></term>
  43             <listitem>
  44                 <para>
  45                     The format of entries in the minmax table.
  46                     Must be one of
  47                     <constant>GL_ALPHA</constant>,
  48                     <constant>GL_ALPHA4</constant>,
  49                     <constant>GL_ALPHA8</constant>,
  50                     <constant>GL_ALPHA12</constant>,
  51                     <constant>GL_ALPHA16</constant>,
  52                     <constant>GL_LUMINANCE</constant>,
  53                     <constant>GL_LUMINANCE4</constant>,
  54                     <constant>GL_LUMINANCE8</constant>,
  55                     <constant>GL_LUMINANCE12</constant>,
  56                     <constant>GL_LUMINANCE16</constant>,
  57                     <constant>GL_LUMINANCE_ALPHA</constant>,
  58                     <constant>GL_LUMINANCE4_ALPHA4</constant>,
  59                     <constant>GL_LUMINANCE6_ALPHA2</constant>,
  60                     <constant>GL_LUMINANCE8_ALPHA8</constant>,
  61                     <constant>GL_LUMINANCE12_ALPHA4</constant>,
  62                     <constant>GL_LUMINANCE12_ALPHA12</constant>,
  63                     <constant>GL_LUMINANCE16_ALPHA16</constant>,
  64                     <constant>GL_R3_G3_B2</constant>,
  65                     <constant>GL_RGB</constant>,
  66                     <constant>GL_RGB4</constant>,
  67                     <constant>GL_RGB5</constant>,
  68                     <constant>GL_RGB8</constant>,
  69                     <constant>GL_RGB10</constant>,
  70                     <constant>GL_RGB12</constant>,
  71                     <constant>GL_RGB16</constant>,
  72                     <constant>GL_RGBA</constant>,
  73                     <constant>GL_RGBA2</constant>,
  74                     <constant>GL_RGBA4</constant>,
  75                     <constant>GL_RGB5_A1</constant>,
  76                     <constant>GL_RGBA8</constant>,
  77                     <constant>GL_RGB10_A2</constant>,
  78                     <constant>GL_RGBA12</constant>, or
  79                     <constant>GL_RGBA16</constant>.
  80                 </para>
  81             </listitem>
  82         </varlistentry>
  83         <varlistentry>
  84             <term><parameter>sink</parameter></term>
  85             <listitem>
  86                 <para>
  87                     If <constant>GL_TRUE</constant>, pixels will be consumed by the minmax
  88                     process and no drawing or texture loading will take place.
  89                     If <constant>GL_FALSE</constant>, pixels will proceed to the final conversion process after
  90                     minmax.
  91                 </para>
  92             </listitem>
  93         </varlistentry>
  94         </variablelist>
  95     </refsect1>
  96     <refsect1 id="description"><title>Description</title>
  97         <para>
  98             When <constant>GL_MINMAX</constant> is enabled, the RGBA components of incoming pixels are
  99             compared to the minimum and maximum values for each component, which are
 100             stored in the two-element minmax table.
 101             (The first element stores the minima, and the second element stores
 102             the maxima.)
 103             If a pixel component is greater than the corresponding component
 104             in the maximum element, then the maximum element is updated with the
 105             pixel component value.
 106             If a pixel component is less than the corresponding component in
 107             the minimum element, then the minimum element is updated with the
 108             pixel component value.
 109             (In both cases, if the internal format of the minmax table includes
 110             luminance, then the R color component of incoming pixels is used
 111             for comparison.)
 112             The contents of the minmax table may be retrieved at a later time
 113             by calling <citerefentry><refentrytitle>glGetMinmax</refentrytitle></citerefentry>.
 114             The minmax operation is enabled or disabled by calling <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> or
 115             <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>, respectively, with an argument of <constant>GL_MINMAX</constant>.
 116         </para>
 117         <para>
 118             <function>glMinmax</function> redefines the current minmax table to have entries of the format
 119             specified by <parameter>internalformat</parameter>.
 120             The maximum element is initialized with the smallest possible component
 121             values, and the minimum element is initialized with the largest possible
 122             component values.
 123             The values in the previous minmax table, if any, are lost.
 124             If <parameter>sink</parameter> is <constant>GL_TRUE</constant>, then pixels are discarded after minmax;
 125             no further processing of the pixels takes place, and no drawing,
 126             texture loading, or pixel readback will result.
 127         </para>
 128         <para>
 129         </para>
 130     </refsect1>
 131     <refsect1 id="notes"><title>Notes</title>
 132         <para>
 133             <function>glMinmax</function> is present only if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>
 134             is called with an argument of <constant>GL_EXTENSIONS</constant>.
 135         </para>
 136     </refsect1>
 137     <refsect1 id="errors"><title>Errors</title>
 138         <para>
 139             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not one of the allowable
 140             values.
 141         </para>
 142         <para>
 143             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the
 144             allowable values.
 145         </para>
 146         <para>
 147             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glMinmax</function> is executed
 148             between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding
 149             execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
 150         </para>
 151     </refsect1>
 152     <refsect1 id="associatedgets"><title>Associated Gets</title>
 153         <para>
 154             <citerefentry><refentrytitle>glGetMinmaxParameter</refentrytitle></citerefentry>
 155         </para>
 156     </refsect1>
 157     <refsect1 id="seealso"><title>See Also</title>
 158         <para>
 159             <citerefentry><refentrytitle>glGetMinmax</refentrytitle></citerefentry>,
 160             <citerefentry><refentrytitle>glResetMinmax</refentrytitle></citerefentry>
 161         </para>
 162     </refsect1>
 163     <refsect1 id="Copyright"><title>Copyright</title>
 164         <para>
 165             Copyright <trademark class="copyright"></trademark> 1991-2006
 166             Silicon Graphics, Inc. This document is licensed under the SGI
 167             Free Software B License. For details, see
 168             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 169         </para>
 170     </refsect1>
 171 </refentry>