205 lines
9.8 KiB
XML
205 lines
9.8 KiB
XML
<?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="glHistogram">
|
|
<refmeta>
|
|
<refmetainfo>
|
|
<copyright>
|
|
<year>1991-2006</year>
|
|
<holder>Silicon Graphics, Inc.</holder>
|
|
</copyright>
|
|
</refmetainfo>
|
|
<refentrytitle>glHistogram</refentrytitle>
|
|
<manvolnum>3G</manvolnum>
|
|
</refmeta>
|
|
<refnamediv>
|
|
<refname>glHistogram</refname>
|
|
<refpurpose>define histogram table</refpurpose>
|
|
</refnamediv>
|
|
<refsynopsisdiv><title>C Specification</title>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>void <function>glHistogram</function></funcdef>
|
|
<paramdef>GLenum <parameter>target</parameter></paramdef>
|
|
<paramdef>GLsizei <parameter>width</parameter></paramdef>
|
|
<paramdef>GLenum <parameter>internalformat</parameter></paramdef>
|
|
<paramdef>GLboolean <parameter>sink</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
<!-- eqn: ignoring delim $$ -->
|
|
<refsect1 id="parameters"><title>Parameters</title>
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><parameter>target</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
The histogram whose parameters are to be set.
|
|
Must be one of
|
|
<constant>GL_HISTOGRAM</constant> or
|
|
<constant>GL_PROXY_HISTOGRAM</constant>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>width</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
The number of entries in the histogram table. Must be a power of 2.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>internalformat</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
The format of entries in the histogram table.
|
|
Must be one of
|
|
<constant>GL_ALPHA</constant>,
|
|
<constant>GL_ALPHA4</constant>,
|
|
<constant>GL_ALPHA8</constant>,
|
|
<constant>GL_ALPHA12</constant>,
|
|
<constant>GL_ALPHA16</constant>,
|
|
<constant>GL_LUMINANCE</constant>,
|
|
<constant>GL_LUMINANCE4</constant>,
|
|
<constant>GL_LUMINANCE8</constant>,
|
|
<constant>GL_LUMINANCE12</constant>,
|
|
<constant>GL_LUMINANCE16</constant>,
|
|
<constant>GL_LUMINANCE_ALPHA</constant>,
|
|
<constant>GL_LUMINANCE4_ALPHA4</constant>,
|
|
<constant>GL_LUMINANCE6_ALPHA2</constant>,
|
|
<constant>GL_LUMINANCE8_ALPHA8</constant>,
|
|
<constant>GL_LUMINANCE12_ALPHA4</constant>,
|
|
<constant>GL_LUMINANCE12_ALPHA12</constant>,
|
|
<constant>GL_LUMINANCE16_ALPHA16</constant>,
|
|
<constant>GL_R3_G3_B2</constant>,
|
|
<constant>GL_RGB</constant>,
|
|
<constant>GL_RGB4</constant>,
|
|
<constant>GL_RGB5</constant>,
|
|
<constant>GL_RGB8</constant>,
|
|
<constant>GL_RGB10</constant>,
|
|
<constant>GL_RGB12</constant>,
|
|
<constant>GL_RGB16</constant>,
|
|
<constant>GL_RGBA</constant>,
|
|
<constant>GL_RGBA2</constant>,
|
|
<constant>GL_RGBA4</constant>,
|
|
<constant>GL_RGB5_A1</constant>,
|
|
<constant>GL_RGBA8</constant>,
|
|
<constant>GL_RGB10_A2</constant>,
|
|
<constant>GL_RGBA12</constant>, or
|
|
<constant>GL_RGBA16</constant>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>sink</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
If <constant>GL_TRUE</constant>, pixels will be consumed by the histogramming
|
|
process and no drawing or texture loading will take place.
|
|
If <constant>GL_FALSE</constant>, pixels will proceed to the minmax process after
|
|
histogramming.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</refsect1>
|
|
<refsect1 id="description"><title>Description</title>
|
|
<para>
|
|
When <constant>GL_HISTOGRAM</constant> is enabled, RGBA color components are converted to
|
|
histogram table indices by clamping to the range [0,1], multiplying by
|
|
the width of the histogram table, and rounding to the nearest integer.
|
|
The table entries selected by the RGBA indices are then incremented.
|
|
(If the internal format of the histogram table includes luminance, then
|
|
the index derived from the R color component determines the luminance
|
|
table entry to be incremented.) If a histogram table entry is incremented
|
|
beyond its maximum value, then its value becomes undefined. (This is
|
|
not an error.)
|
|
</para>
|
|
<para>
|
|
Histogramming is performed only for RGBA pixels (though these may
|
|
be specified originally as color indices and converted to RGBA by
|
|
index table lookup).
|
|
Histogramming is enabled with <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and disabled with <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>.
|
|
</para>
|
|
<para>
|
|
When <parameter>target</parameter> is <constant>GL_HISTOGRAM</constant>, <function>glHistogram</function> redefines the current
|
|
histogram table to have <parameter>width</parameter> entries of the format specified by
|
|
<parameter>internalformat</parameter>.
|
|
The entries are indexed 0 through
|
|
<inlineequation><mml:math>
|
|
<!-- eqn: width - 1:-->
|
|
<mml:mrow>
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
|
<mml:mo>-</mml:mo>
|
|
<mml:mn>1</mml:mn>
|
|
</mml:mrow>
|
|
</mml:math></inlineequation>,
|
|
and
|
|
all entries are initialized to zero.
|
|
The values in the previous histogram table, if any, are lost.
|
|
If <parameter>sink</parameter> is <constant>GL_TRUE</constant>, then pixels are discarded after histogramming;
|
|
no further processing of the pixels takes place, and no drawing,
|
|
texture loading, or pixel readback will result.
|
|
</para>
|
|
<para>
|
|
When <parameter>target</parameter> is <constant>GL_PROXY_HISTOGRAM</constant>, <function>glHistogram</function> computes all
|
|
state information as if the histogram table were to be redefined,
|
|
but does not actually define the new table.
|
|
If the requested histogram table is too large to be supported, then the
|
|
state information will be set to zero.
|
|
This provides a way to determine if a histogram table with the given
|
|
parameters can be supported.
|
|
</para>
|
|
<para>
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="notes"><title>Notes</title>
|
|
<para>
|
|
<function>glHistogram</function> is present only if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>
|
|
is called with an argument of <constant>GL_EXTENSIONS</constant>.
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="errors"><title>Errors</title>
|
|
<para>
|
|
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not one of the allowable
|
|
values.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_VALUE</constant> is generated if <parameter>width</parameter> is less than zero or is
|
|
not a power of 2.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the
|
|
allowable values.
|
|
</para>
|
|
<para>
|
|
<constant>GL_TABLE_TOO_LARGE</constant> is generated if <parameter>target</parameter> is <constant>GL_HISTOGRAM</constant>
|
|
and the histogram table specified is too large for the implementation.
|
|
</para>
|
|
<para>
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glHistogram</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>glGetHistogramParameter</refentrytitle></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
<refsect1 id="seealso"><title>See Also</title>
|
|
<para>
|
|
<citerefentry><refentrytitle>glGetHistogram</refentrytitle></citerefentry>,
|
|
<citerefentry><refentrytitle>glResetHistogram</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>
|