<div class="refentry" lang="en" xml:lang="en"><a id="glConvolutionParameter"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glConvolutionParameter — set convolution parameters</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glConvolutionParameterf</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat  </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glConvolutionParameteri</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div></div><p>

</p><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>target</code></em></span></dt><dd><p>

The target for the convolution parameter.

Must be one of

<code class="constant">GL_CONVOLUTION_1D</code>,

<code class="constant">GL_CONVOLUTION_2D</code>, or

<code class="constant">GL_SEPARABLE_2D</code>.

</p></dd><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p>

The parameter to be set.

Must be

<code class="constant">GL_CONVOLUTION_BORDER_MODE</code>.

</p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p>

The parameter value.

Must be one of

<code class="constant">GL_REDUCE</code>, <code class="constant">GL_CONSTANT_BORDER</code>, <code class="constant">GL_REPLICATE_BORDER</code>.

</p><p>

</p></dd></dl></div></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glConvolutionParameterfv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLfloat *  </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glConvolutionParameteriv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>const GLint *  </td><td><var class="pdparam">params</var><code>)</code>;</td></tr></table></div></div><p>

</p><div class="refsect1" lang="en" xml:lang="en"><a id="parameters2"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>target</code></em></span></dt><dd><p>

The target for the convolution parameter.

Must be one of

<code class="constant">GL_CONVOLUTION_1D</code>,

<code class="constant">GL_CONVOLUTION_2D</code>, or

<code class="constant">GL_SEPARABLE_2D</code>.

</p></dd><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p>

The parameter to be set.

Must be one of

<code class="constant">GL_CONVOLUTION_BORDER_MODE</code>,

<code class="constant">GL_CONVOLUTION_BORDER_COLOR</code>,

<code class="constant">GL_CONVOLUTION_FILTER_SCALE</code>, or

<code class="constant">GL_CONVOLUTION_FILTER_BIAS</code>.

</p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p>

The parameter value.

If <em class="parameter"><code>pname</code></em>v is <code class="constant">GL_CONVOLUTION_BORDER_MODE</code>, <em class="parameter"><code>params</code></em>v must be one of

<code class="constant">GL_REDUCE</code>, <code class="constant">GL_CONSTANT_BORDER</code>, or <code class="constant">GL_REPLICATE_BORDER</code>.

Otherwise, must be a vector of four values (for red, green, blue, and alpha,

respectively) to be used for

scaling (when <em class="parameter"><code>pname</code></em>v is <code class="constant">GL_CONVOLUTION_FILTER_SCALE</code>), or

biasing (when <em class="parameter"><code>pname</code></em>v is <code class="constant">GL_CONVOLUTION_FILTER_BIAS</code>) a convolution

filter kernel or setting the constant border color (when <em class="parameter"><code>pname</code></em>v is

<code class="constant">GL_CONVOLUTION_BORDER_COLOR</code>.

</p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>

<code class="function">glConvolutionParameter</code> sets the value of a convolution parameter.

</p><p>

<em class="parameter"><code>target</code></em> selects the convolution filter to be affected:

<code class="constant">GL_CONVOLUTION_1D</code>,

<code class="constant">GL_CONVOLUTION_2D</code>, or

<code class="constant">GL_SEPARABLE_2D</code>

for the 1D, 2D, or separable 2D filter, respectively.

</p><p>

<em class="parameter"><code>pname</code></em> selects the parameter to be changed.

<code class="constant">GL_CONVOLUTION_FILTER_SCALE</code> and <code class="constant">GL_CONVOLUTION_FILTER_BIAS</code>

affect the definition of the convolution filter kernel; see

<a class="citerefentry" href="glConvolutionFilter1D"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter1D</span></span></a>, <a class="citerefentry" href="glConvolutionFilter2D"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter2D</span></span></a>, and

<a class="citerefentry" href="glSeparableFilter2D"><span class="citerefentry"><span class="refentrytitle">glSeparableFilter2D</span></span></a> for details.

In these cases, <em class="parameter"><code>params</code></em>v is an array of four values to be applied to

red, green, blue, and alpha values, respectively. The initial value for

<code class="constant">GL_CONVOLUTION_FILTER_SCALE</code> is (1, 1, 1, 1), and the initial value

for <code class="constant">GL_CONVOLUTION_FILTER_BIAS</code> is (0, 0, 0, 0).

</p><p>

A <em class="parameter"><code>pname</code></em> value of <code class="constant">GL_CONVOLUTION_BORDER_MODE</code> controls the

convolution border mode. The accepted modes are:

</p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_REDUCE</code></span></dt><dd><p>

The image resulting from convolution is

smaller than the source image.

If the filter width is

<math overflow="scroll"><mi mathvariant="italic">Wf</mi></math>

and height is

<math overflow="scroll"><mi mathvariant="italic">Hf</mi></math>,

and the source image width is

<math overflow="scroll"><mi mathvariant="italic">Ws</mi></math>

and height is

<math overflow="scroll"><mi mathvariant="italic">Hs</mi></math>,

then the convolved image width will be

<math overflow="scroll">

<mrow>

<mi mathvariant="italic">Ws</mi>

<mo>-</mo>

<mi mathvariant="italic">Wf</mi>

<mo>+</mo>

<mn>1</mn>

</mrow>

</math>

and height

will be

<math overflow="scroll">

<mrow>

<mi mathvariant="italic">Hs</mi>

<mo>-</mo>

<mi mathvariant="italic">Hf</mi>

<mo>+</mo>

<mn>1</mn>

</mrow>

</math>.

(If this reduction would generate an image with zero or negative width

and/or height, the output is simply null, with no error generated.)

The coordinates of the image resulting from convolution are zero

through

<math overflow="scroll">

<mrow>

<mi mathvariant="italic">Ws</mi>

<mo>-</mo>

<mi mathvariant="italic">Wf</mi>

</mrow>

</math>

in width and zero through

<math overflow="scroll">

<mrow>

<mi mathvariant="italic">Hs</mi>

<mo>-</mo>

<mi mathvariant="italic">Hf</mi>

</mrow>

</math>

in

height.

</p></dd><dt><span class="term"><code class="constant">GL_CONSTANT_BORDER</code></span></dt><dd><p>

The image resulting from convolution is the same size as the source image, and

processed as if the source image were surrounded by pixels with their color

specified by the <code class="constant">GL_CONVOLUTION_BORDER_COLOR</code>.

</p></dd><dt><span class="term"><code class="constant">GL_REPLICATE_BORDER</code></span></dt><dd><p>

The image resulting from convolution is the same size as the source image, and

processed as if the outermost pixel on the border of the source image were

replicated.

</p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>

<code class="function">glConvolutionParameter</code> is present only if <code class="code">ARB_imaging</code> is returned when <a class="citerefentry" href="glGetString"><span class="citerefentry"><span class="refentrytitle">glGetString</span></span></a>

is called with an argument of <code class="constant">GL_EXTENSIONS</code>.

</p><p>

In cases where errors can result from the specification of invalid

image dimensions, it is the dimensions after convolution that are

tested, not the dimensions of the source image.

For example, <a class="citerefentry" href="glTexImage1D"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a> requires power-of-two image size.

When <code class="constant">GL_REDUCE</code> border mode is in effect,

the source image must be larger than the final power-of-two size

by one less than the size of the 1D filter kernel.

</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>

<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>target</code></em> is not one of the allowable

values.

</p><p>

<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>pname</code></em> is not one of the allowable

values.

</p><p>

<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>pname</code></em> is

<code class="constant">GL_CONVOLUTION_BORDER_MODE</code> and <em class="parameter"><code>params</code></em> is not one of

<code class="constant">GL_REDUCE</code>, <code class="constant">GL_CONSTANT_BORDER</code>, or <code class="constant">GL_REPLICATE_BORDER</code>.

</p><p>

<code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glConvolutionParameter</code> is executed

between the execution of <a class="citerefentry" href="glBegin"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> and the corresponding

execution of <a class="citerefentry" href="glEnd"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.

</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>

<a class="citerefentry" href="glGetConvolutionParameter"><span class="citerefentry"><span class="refentrytitle">glGetConvolutionParameter</span></span></a>

</p></div>

{$pipelinestall}{$examples}

<div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>

<a class="citerefentry" href="glConvolutionFilter1D"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter1D</span></span></a>,

<a class="citerefentry" href="glConvolutionFilter2D"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter2D</span></span></a>,

<a class="citerefentry" href="glSeparableFilter2D"><span class="citerefentry"><span class="refentrytitle">glSeparableFilter2D</span></span></a>,

<a class="citerefentry" href="glGetConvolutionParameter"><span class="citerefentry"><span class="refentrytitle">glGetConvolutionParameter</span></span></a>

</p></div><div class="refsect1" lang="en" xml:lang="en"><div id="Copyright"><h2>Copyright</h2><p>

Copyright © 1991-2006

Silicon Graphics, Inc. This document is licensed under the SGI

Free Software B License. For details, see

<a class="ulink" href="https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/" target="_top">https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/</a>.

</p></div></div></div>