[clinton/guile-figl.git] / upstream-doc / man2 / glHistogram.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>
Commit	Line	Data
7faf1d71 AW	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="glHistogram">
	5	<refmeta>
	6	<refmetainfo>
	7	<copyright>
	8	<year>1991-2006</year>
	9	<holder>Silicon Graphics, Inc.</holder>
	10	</copyright>
	11	</refmetainfo>
	12	<refentrytitle>glHistogram</refentrytitle>
	13	<manvolnum>3G</manvolnum>
	14	</refmeta>
	15	<refnamediv>
	16	<refname>glHistogram</refname>
	17	<refpurpose>define histogram table</refpurpose>
	18	</refnamediv>
	19	<refsynopsisdiv><title>C Specification</title>
	20	<funcsynopsis>
	21	<funcprototype>
	22	<funcdef>void <function>glHistogram</function></funcdef>
	23	<paramdef>GLenum <parameter>target</parameter></paramdef>
	24	<paramdef>GLsizei <parameter>width</parameter></paramdef>
	25	<paramdef>GLenum <parameter>internalformat</parameter></paramdef>
	26	<paramdef>GLboolean <parameter>sink</parameter></paramdef>
	27	</funcprototype>
	28	</funcsynopsis>
	29	</refsynopsisdiv>
	30	<!-- eqn: ignoring delim $$ -->
	31	<refsect1 id="parameters"><title>Parameters</title>
	32	<variablelist>
	33	<varlistentry>
	34	<term><parameter>target</parameter></term>
	35	<listitem>
	36	<para>
	37	The histogram whose parameters are to be set.
	38	Must be one of
	39	<constant>GL_HISTOGRAM</constant> or
	40	<constant>GL_PROXY_HISTOGRAM</constant>.
	41	</para>
	42	</listitem>
	43	</varlistentry>
	44	<varlistentry>
	45	<term><parameter>width</parameter></term>
	46	<listitem>
	47	<para>
	48	The number of entries in the histogram table. Must be a power of 2.
	49	</para>
	50	</listitem>
	51	</varlistentry>
	52	<varlistentry>
	53	<term><parameter>internalformat</parameter></term>
	54	<listitem>
	55	<para>
	56	The format of entries in the histogram table.
	57	Must be one of
	58	<constant>GL_ALPHA</constant>,
	59	<constant>GL_ALPHA4</constant>,
	60	<constant>GL_ALPHA8</constant>,
	61	<constant>GL_ALPHA12</constant>,
	62	<constant>GL_ALPHA16</constant>,
	63	<constant>GL_LUMINANCE</constant>,
	64	<constant>GL_LUMINANCE4</constant>,
65	<constant>GL_LUMINANCE8</constant>,
66	<constant>GL_LUMINANCE12</constant>,
67	<constant>GL_LUMINANCE16</constant>,
68	<constant>GL_LUMINANCE_ALPHA</constant>,
69	<constant>GL_LUMINANCE4_ALPHA4</constant>,
70	<constant>GL_LUMINANCE6_ALPHA2</constant>,
71	<constant>GL_LUMINANCE8_ALPHA8</constant>,
72	<constant>GL_LUMINANCE12_ALPHA4</constant>,
73	<constant>GL_LUMINANCE12_ALPHA12</constant>,
74	<constant>GL_LUMINANCE16_ALPHA16</constant>,
75	<constant>GL_R3_G3_B2</constant>,
76	<constant>GL_RGB</constant>,
77	<constant>GL_RGB4</constant>,
78	<constant>GL_RGB5</constant>,
79	<constant>GL_RGB8</constant>,
80	<constant>GL_RGB10</constant>,
81	<constant>GL_RGB12</constant>,
82	<constant>GL_RGB16</constant>,
83	<constant>GL_RGBA</constant>,
84	<constant>GL_RGBA2</constant>,
85	<constant>GL_RGBA4</constant>,
86	<constant>GL_RGB5_A1</constant>,
87	<constant>GL_RGBA8</constant>,
88	<constant>GL_RGB10_A2</constant>,
89	<constant>GL_RGBA12</constant>, or
90	<constant>GL_RGBA16</constant>.
91	</para>
92	</listitem>
93	</varlistentry>
94	<varlistentry>
95	<term><parameter>sink</parameter></term>
96	<listitem>
97	<para>
98	If <constant>GL_TRUE</constant>, pixels will be consumed by the histogramming
99	process and no drawing or texture loading will take place.
100	If <constant>GL_FALSE</constant>, pixels will proceed to the minmax process after
101	histogramming.
102	</para>
103	</listitem>
104	</varlistentry>
105	</variablelist>
106	</refsect1>
107	<refsect1 id="description"><title>Description</title>
108	<para>
109	When <constant>GL_HISTOGRAM</constant> is enabled, RGBA color components are converted to
110	histogram table indices by clamping to the range [0,1], multiplying by
111	the width of the histogram table, and rounding to the nearest integer.
112	The table entries selected by the RGBA indices are then incremented.
113	(If the internal format of the histogram table includes luminance, then
114	the index derived from the R color component determines the luminance
115	table entry to be incremented.) If a histogram table entry is incremented
116	beyond its maximum value, then its value becomes undefined. (This is
117	not an error.)
118	</para>
119	<para>
120	Histogramming is performed only for RGBA pixels (though these may
121	be specified originally as color indices and converted to RGBA by
122	index table lookup).
123	Histogramming is enabled with <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and disabled with <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>.
124	</para>
125	<para>
126	When <parameter>target</parameter> is <constant>GL_HISTOGRAM</constant>, <function>glHistogram</function> redefines the current
127	histogram table to have <parameter>width</parameter> entries of the format specified by
128	<parameter>internalformat</parameter>.
129	The entries are indexed 0 through
130	<inlineequation><mml:math>
131	<!-- eqn: width - 1:-->
132	<mml:mrow>
133	<mml:mi mathvariant="italic">width</mml:mi>
134	<mml:mo>-</mml:mo>
135	<mml:mn>1</mml:mn>
136	</mml:mrow>
137	</mml:math></inlineequation>,
138	and
139	all entries are initialized to zero.
140	The values in the previous histogram table, if any, are lost.
141	If <parameter>sink</parameter> is <constant>GL_TRUE</constant>, then pixels are discarded after histogramming;
142	no further processing of the pixels takes place, and no drawing,
143	texture loading, or pixel readback will result.
144	</para>
145	<para>
146	When <parameter>target</parameter> is <constant>GL_PROXY_HISTOGRAM</constant>, <function>glHistogram</function> computes all
147	state information as if the histogram table were to be redefined,
148	but does not actually define the new table.
149	If the requested histogram table is too large to be supported, then the
150	state information will be set to zero.
151	This provides a way to determine if a histogram table with the given
152	parameters can be supported.
153	</para>
154	<para>
155	</para>
156	</refsect1>
157	<refsect1 id="notes"><title>Notes</title>
158	<para>
159	<function>glHistogram</function> is present only if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry>
160	is called with an argument of <constant>GL_EXTENSIONS</constant>.
161	</para>
162	</refsect1>
163	<refsect1 id="errors"><title>Errors</title>
164	<para>
165	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not one of the allowable
166	values.
167	</para>
168	<para>
169	<constant>GL_INVALID_VALUE</constant> is generated if <parameter>width</parameter> is less than zero or is
170	not a power of 2.
171	</para>
172	<para>
173	<constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the
174	allowable values.
175	</para>
176	<para>
177	<constant>GL_TABLE_TOO_LARGE</constant> is generated if <parameter>target</parameter> is <constant>GL_HISTOGRAM</constant>
178	and the histogram table specified is too large for the implementation.
179	</para>
180	<para>
181	<constant>GL_INVALID_OPERATION</constant> is generated if <function>glHistogram</function> is executed
182	between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding
183	execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
184	</para>
185	</refsect1>
186	<refsect1 id="associatedgets"><title>Associated Gets</title>
187	<para>
188	<citerefentry><refentrytitle>glGetHistogramParameter</refentrytitle></citerefentry>
189	</para>
190	</refsect1>
191	<refsect1 id="seealso"><title>See Also</title>
192	<para>
193	<citerefentry><refentrytitle>glGetHistogram</refentrytitle></citerefentry>,
194	<citerefentry><refentrytitle>glResetHistogram</refentrytitle></citerefentry>
195	</para>
196	</refsect1>
197	<refsect1 id="Copyright"><title>Copyright</title>
198	<para>
199	Copyright <trademark class="copyright"></trademark> 1991-2006
200	Silicon Graphics, Inc. This document is licensed under the SGI
201	Free Software B License. For details, see
202	<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
203	</para>
204	</refsect1>
205	</refentry>