Subversion Repositories AndroidProjects

<?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="glSeparableFilter2D">

    <refmeta>

        <refmetainfo>

            <copyright>

                <year>1991-2006</year>

                <holder>Silicon Graphics, Inc.</holder>

            </copyright>

        </refmetainfo>

        <refentrytitle>glSeparableFilter2D</refentrytitle>

        <manvolnum>3G</manvolnum>

    </refmeta>

    <refnamediv>

        <refname>glSeparableFilter2D</refname>

        <refpurpose>define a separable two-dimensional convolution filter</refpurpose>

    </refnamediv>

    <refsynopsisdiv><title>C Specification</title>

        <funcsynopsis>

            <funcprototype>

                <funcdef>void <function>glSeparableFilter2D</function></funcdef>

                <paramdef>GLenum <parameter>target</parameter></paramdef>

                <paramdef>GLenum <parameter>internalformat</parameter></paramdef>

                <paramdef>GLsizei <parameter>width</parameter></paramdef>

                <paramdef>GLsizei <parameter>height</parameter></paramdef>

                <paramdef>GLenum <parameter>format</parameter></paramdef>

                <paramdef>GLenum <parameter>type</parameter></paramdef>

                <paramdef>const GLvoid * <parameter>row</parameter></paramdef>

                <paramdef>const GLvoid * <parameter>column</parameter></paramdef>

            </funcprototype>

        </funcsynopsis>

    </refsynopsisdiv>

    <refsect1 id="parameters"><title>Parameters</title>

        <variablelist>

        <varlistentry>

            <term><parameter>target</parameter></term>

            <listitem>

                <para>

                    Must be <constant>GL_SEPARABLE_2D</constant>.

                </para>

            </listitem>

        </varlistentry>

        <varlistentry>

            <term><parameter>internalformat</parameter></term>

            <listitem>

                <para>

                    The internal format of the convolution filter kernel.

                    The allowable values are

                    <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_INTENSITY</constant>,

                    <constant>GL_INTENSITY4</constant>,

                    <constant>GL_INTENSITY8</constant>,

                    <constant>GL_INTENSITY12</constant>,

                    <constant>GL_INTENSITY16</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>width</parameter></term>

            <listitem>

                <para>

                    The number of elements in the pixel array referenced by <parameter>row</parameter>.

                    (This is the width of the separable filter kernel.)

                </para>

            </listitem>

        </varlistentry>

        <varlistentry>

            <term><parameter>height</parameter></term>

            <listitem>

                <para>

                    The number of elements in the pixel array referenced by <parameter>column</parameter>.

                    (This is the height of the separable filter kernel.)

                </para>

            </listitem>

        </varlistentry>

        <varlistentry>

            <term><parameter>format</parameter></term>

            <listitem>

                <para>

                    The format of the pixel data in <parameter>row</parameter> and <parameter>column</parameter>.

                    The allowable values are

                    <constant>GL_RED</constant>,

                    <constant>GL_GREEN</constant>,

                    <constant>GL_BLUE</constant>,

                    <constant>GL_ALPHA</constant>,

                    <constant>GL_RGB</constant>,

                    <constant>GL_BGR</constant>,

                    <constant>GL_RGBA</constant>,

                    <constant>GL_BGRA</constant>,

                    <constant>GL_INTENSITY</constant>,

                    <constant>GL_LUMINANCE</constant>, and

                    <constant>GL_LUMINANCE_ALPHA</constant>.

                </para>

            </listitem>

        </varlistentry>

        <varlistentry>

            <term><parameter>type</parameter></term>

            <listitem>

                <para>

                    The type of the pixel data in <parameter>row</parameter> and <parameter>column</parameter>.

                    Symbolic constants

                    <constant>GL_UNSIGNED_BYTE</constant>,

                    <constant>GL_BYTE</constant>,

                    <constant>GL_BITMAP</constant>,

                    <constant>GL_UNSIGNED_SHORT</constant>,

                    <constant>GL_SHORT</constant>,

                    <constant>GL_UNSIGNED_INT</constant>,

                    <constant>GL_INT</constant>,

                    <constant>GL_FLOAT</constant>,

                    <constant>GL_UNSIGNED_BYTE_3_3_2</constant>,

                    <constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>,

                    <constant>GL_UNSIGNED_SHORT_5_6_5</constant>,

                    <constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>,

                    <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>,

                    <constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>,

                    <constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>,

                    <constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>,

                    <constant>GL_UNSIGNED_INT_8_8_8_8</constant>,

                    <constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>,

                    <constant>GL_UNSIGNED_INT_10_10_10_2</constant>, and

                    <constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>

                    are accepted.

                </para>

            </listitem>

        </varlistentry>

        <varlistentry>

            <term><parameter>row</parameter></term>

            <listitem>

                <para>

                    Pointer to a one-dimensional array of pixel data that is processed to

                    build the row filter kernel.

                </para>

            </listitem>

        </varlistentry>

        <varlistentry>

            <term><parameter>column</parameter></term>

            <listitem>

                <para>

                    Pointer to a one-dimensional array of pixel data that is processed to

                    build the column filter kernel.

                </para>

            </listitem>

        </varlistentry>

        </variablelist>

    </refsect1>

    <refsect1 id="description"><title>Description</title>

        <para>

            <function>glSeparableFilter2D</function> builds a two-dimensional separable convolution filter kernel from

            two arrays of pixels.

        </para>

        <para>

            The pixel arrays specified by (<parameter>width</parameter>, <parameter>format</parameter>, <parameter>type</parameter>, <parameter>row</parameter>)

            and (<parameter>height</parameter>, <parameter>format</parameter>, <parameter>type</parameter>, <parameter>column</parameter>) are processed just as if

            they had been passed to <citerefentry><refentrytitle>glDrawPixels</refentrytitle></citerefentry>,

            but processing stops after the final expansion to RGBA is completed.

        </para>

        <para>

            If a non-zero named buffer object is bound to the <constant>GL_PIXEL_UNPACK_BUFFER</constant> target

            (see <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>) while a convolution filter is

            specified, <parameter>row</parameter> and <parameter>column</parameter> are treated as byte offsets into the buffer object's data store.

        </para>

        <para>

            Next, the R, G, B, and A components of all pixels in both arrays are scaled

            by the four separable 2D <constant>GL_CONVOLUTION_FILTER_SCALE</constant> parameters and

            biased by the four separable 2D <constant>GL_CONVOLUTION_FILTER_BIAS</constant> parameters.

            (The scale and bias parameters are set by <citerefentry><refentrytitle>glConvolutionParameter</refentrytitle></citerefentry>

            using the <constant>GL_SEPARABLE_2D</constant> target and the names

            <constant>GL_CONVOLUTION_FILTER_SCALE</constant> and <constant>GL_CONVOLUTION_FILTER_BIAS</constant>.

            The parameters themselves are vectors of four values that are applied to red,

            green, blue, and alpha, in that order.)

            The R, G, B, and A values are not clamped to [0,1] at any time during this

            process.

        </para>

        <para>

            Each pixel is then converted to the internal format specified by

            <parameter>internalformat</parameter>.

            This conversion simply maps the component values of the pixel (R, G, B,

            and A) to the values included in the internal format (red, green, blue,

            alpha, luminance, and intensity).  The mapping is as follows:

        </para>

        <informaltable frame="topbot">

            <tgroup cols="7" align="left">

                <colspec colwidth="2.5*" />

                <colspec colwidth="1*" align="center"/>

                <colspec colwidth="1*"  align="center"/>

                <colspec colwidth="1*"  align="center"/>

                <colspec colwidth="1*"  align="center"/>

                <colspec colwidth="1.5*"  align="center"/>

                <colspec colwidth="1.5*"  align="center"/>

                <thead>

                    <row>

                        <entry rowsep="1" align="left"><emphasis role="bold">

                        Internal Format

                        </emphasis></entry>

                        <entry rowsep="1" align="center"><emphasis role="bold">

                        Red

                        </emphasis></entry>

                        <entry rowsep="1" align="center"><emphasis role="bold">

                        Green

                        </emphasis></entry>

                        <entry rowsep="1" align="center"><emphasis role="bold">

                        Blue

                        </emphasis></entry>

                        <entry rowsep="1" align="center"><emphasis role="bold">

                        Alpha

                        </emphasis></entry>

                        <entry rowsep="1" align="center"><emphasis role="bold">

                        Luminance

                        </emphasis></entry>

                        <entry rowsep="1" align="center"><emphasis role="bold">

                        Intensity

                        </emphasis></entry>

                    </row>

                </thead>

                <tbody>

                    <row>

                        <entry align="left">

                        <constant>GL_LUMINANCE</constant>

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        R

                        </entry>

                        <entry align="center">

                        </entry>

                    </row>

                    <row>

                        <entry align="left">

                        <constant>GL_LUMINANCE_ALPHA</constant>

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        A

                        </entry>

                        <entry align="center">

                        R

                        </entry>

                        <entry align="center">

                        </entry>

                    </row>

                    <row>

                        <entry align="left">

                        <constant>GL_INTENSITY</constant>

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        R

                        </entry>

                    </row>

                    <row>

                        <entry align="left">

                        <constant>GL_RGB</constant>

                        </entry>

                        <entry align="center">

                        R

                        </entry>

                        <entry align="center">

                        G

                        </entry>

                        <entry align="center">

                        B

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                    </row>

                    <row>

                        <entry align="left">

                        <constant>GL_RGBA</constant>

                        </entry>

                        <entry align="center">

                        R

                        </entry>

                        <entry align="center">

                        G

                        </entry>

                        <entry align="center">

                        B

                        </entry>

                        <entry align="center">

                        A

                        </entry>

                        <entry align="center">

                        </entry>

                        <entry align="center">

                        </entry>

                    </row>

                </tbody>

            </tgroup>

        </informaltable>

        <para>

            The red, green, blue, alpha, luminance, and/or intensity components of

            the resulting pixels are stored in floating-point rather than integer

            format.

            They form two one-dimensional filter kernel images.

            The row image is indexed by coordinate <emphasis>i</emphasis> starting at zero and

            increasing from left to right.

            Each location in the row image is derived from element <emphasis>i</emphasis> of <parameter>row</parameter>.

            The column image is indexed by coordinate <emphasis>j</emphasis> starting at zero

            and increasing from bottom to top.

            Each location in the column image is derived from element <emphasis>j</emphasis> of <parameter>column</parameter>.

        </para>

        <para>

            Note that after a convolution is performed, the resulting color

            components are also scaled by their corresponding

            <constant>GL_POST_CONVOLUTION_c_SCALE</constant> parameters and biased by their

            corresponding <constant>GL_POST_CONVOLUTION_c_BIAS</constant> parameters (where

            <emphasis>c</emphasis> takes on the values <emphasis role="bold">RED</emphasis>, <emphasis role="bold">GREEN</emphasis>, <emphasis role="bold">BLUE</emphasis>, and

            <emphasis role="bold">ALPHA</emphasis>).

            These parameters are set by <citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry>.

        </para>

    </refsect1>

    <refsect1 id="notes"><title>Notes</title>

        <para>

            <function>glSeparableFilter2D</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

            <constant>GL_SEPARABLE_2D</constant>.

        </para>

        <para>

            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the

            allowable values.

        </para>

        <para>

            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>format</parameter> is not one of the allowable

            values.

        </para>

        <para>

            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>type</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 greater

            than the maximum supported value.

            This value may be queried with <citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry>

            using target <constant>GL_SEPARABLE_2D</constant> and name

            <constant>GL_MAX_CONVOLUTION_WIDTH</constant>.

        </para>

        <para>

            <constant>GL_INVALID_VALUE</constant> is generated if <parameter>height</parameter> is less than zero or greater

            than the maximum supported value.

            This value may be queried with <citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry>

            using target <constant>GL_SEPARABLE_2D</constant> and name

            <constant>GL_MAX_CONVOLUTION_HEIGHT</constant>.

        </para>

        <para>

            <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>height</parameter> is one of

            <constant>GL_UNSIGNED_BYTE_3_3_2</constant>,

            <constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>,

            <constant>GL_UNSIGNED_SHORT_5_6_5</constant>, or

            <constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>

            and <parameter>format</parameter> is not <constant>GL_RGB</constant>.

        </para>

        <para>

            <constant>GL_INVALID_OPERATION</constant> is generated if <parameter>height</parameter> is one of

            <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>,

            <constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>,

            <constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>,

            <constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>,

            <constant>GL_UNSIGNED_INT_8_8_8_8</constant>,

            <constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>,

            <constant>GL_UNSIGNED_INT_10_10_10_2</constant>, or

            <constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>

            and <parameter>format</parameter> is neither <constant>GL_RGBA</constant> nor <constant>GL_BGRA</constant>.

        </para>

        <para>

            <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the

            <constant>GL_PIXEL_UNPACK_BUFFER</constant> target and the buffer object's data store is currently mapped.

        </para>

        <para>

            <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the

            <constant>GL_PIXEL_UNPACK_BUFFER</constant> target and the data would be unpacked from the buffer

            object such that the memory reads required would exceed the data store size.

        </para>

        <para>

            <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the

            <constant>GL_PIXEL_UNPACK_BUFFER</constant> target and <parameter>row</parameter> or

            <parameter>column</parameter> is not evenly divisible

            into the number of bytes needed to store in memory a datum indicated by <parameter>type</parameter>.

        </para>

        <para>

            <constant>GL_INVALID_OPERATION</constant> is generated if <function>glSeparableFilter2D</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>glGetConvolutionParameter</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glGetSeparableFilter</refentrytitle></citerefentry>

        </para>

        <para>

            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_PIXEL_UNPACK_BUFFER_BINDING</constant>

        </para>

    </refsect1>

    <refsect1 id="seealso"><title>See Also</title>

        <para>

            <citerefentry><refentrytitle>glConvolutionFilter1D</refentrytitle></citerefentry>,

            <citerefentry><refentrytitle>glConvolutionFilter2D</refentrytitle></citerefentry>,

            <citerefentry><refentrytitle>glConvolutionParameter</refentrytitle></citerefentry>,

            <citerefentry><refentrytitle>glPixelTransfer</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>