upstream-man-pages/man2/xhtml/glCopyConvolutionFilter2D.xml

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   3 <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glCopyConvolutionFilter2D</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glCopyConvolutionFilter2D"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glCopyConvolutionFilter2D — copy pixels into a two-dimensional convolution filter</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glCopyConvolutionFilter2D</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">internalformat</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei  </td><td><var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei  </td><td><var class="pdparam">height</var><code>)</code>;</td></tr></table></div></div><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>
   4                     Must be <code class="constant">GL_CONVOLUTION_2D</code>.
   5                 </p></dd><dt><span class="term"><em class="parameter"><code>internalformat</code></em></span></dt><dd><p>
   6                     The internal format of the convolution filter kernel.
   7                     The allowable values are
   8                     <code class="constant">GL_ALPHA</code>,
   9                     <code class="constant">GL_ALPHA4</code>,
  10                     <code class="constant">GL_ALPHA8</code>,
  11                     <code class="constant">GL_ALPHA12</code>,
  12                     <code class="constant">GL_ALPHA16</code>,
  13                     <code class="constant">GL_LUMINANCE</code>,
  14                     <code class="constant">GL_LUMINANCE4</code>,
  15                     <code class="constant">GL_LUMINANCE8</code>,
  16                     <code class="constant">GL_LUMINANCE12</code>,
  17                     <code class="constant">GL_LUMINANCE16</code>,
  18                     <code class="constant">GL_LUMINANCE_ALPHA</code>,
  19                     <code class="constant">GL_LUMINANCE4_ALPHA4</code>,
  20                     <code class="constant">GL_LUMINANCE6_ALPHA2</code>,
  21                     <code class="constant">GL_LUMINANCE8_ALPHA8</code>,
  22                     <code class="constant">GL_LUMINANCE12_ALPHA4</code>,
  23                     <code class="constant">GL_LUMINANCE12_ALPHA12</code>,
  24                     <code class="constant">GL_LUMINANCE16_ALPHA16</code>,
  25                     <code class="constant">GL_INTENSITY</code>,
  26                     <code class="constant">GL_INTENSITY4</code>,
  27                     <code class="constant">GL_INTENSITY8</code>,
  28                     <code class="constant">GL_INTENSITY12</code>,
  29                     <code class="constant">GL_INTENSITY16</code>,
  30                     <code class="constant">GL_R3_G3_B2</code>,
  31                     <code class="constant">GL_RGB</code>,
  32                     <code class="constant">GL_RGB4</code>,
  33                     <code class="constant">GL_RGB5</code>,
  34                     <code class="constant">GL_RGB8</code>,
  35                     <code class="constant">GL_RGB10</code>,
  36                     <code class="constant">GL_RGB12</code>,
  37                     <code class="constant">GL_RGB16</code>,
  38                     <code class="constant">GL_RGBA</code>,
  39                     <code class="constant">GL_RGBA2</code>,
  40                     <code class="constant">GL_RGBA4</code>,
  41                     <code class="constant">GL_RGB5_A1</code>,
  42                     <code class="constant">GL_RGBA8</code>,
  43                     <code class="constant">GL_RGB10_A2</code>,
  44                     <code class="constant">GL_RGBA12</code>, or
  45                     <code class="constant">GL_RGBA16</code>.
  46                 </p></dd><dt><span class="term"><em class="parameter"><code>x</code></em>, </span><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p>
  47                     The window space coordinates of the lower-left coordinate of the
  48                     pixel array to copy.
  49                 </p></dd><dt><span class="term"><em class="parameter"><code>width</code></em></span></dt><dd><p>
  50                     The width of the pixel array to copy.
  51                 </p></dd><dt><span class="term"><em class="parameter"><code>height</code></em></span></dt><dd><p>
  52                     The height of the pixel array to copy.
  53                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  54             <code class="function">glCopyConvolutionFilter2D</code> defines a two-dimensional convolution filter kernel with pixels
  55             from the current <code class="constant">GL_READ_BUFFER</code> (rather than from main memory,
  56             as is the case for <a class="citerefentry" href="glConvolutionFilter2D.xml"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter2D</span></span></a>).
  57         </p><p>
  58             The screen-aligned pixel rectangle with lower-left corner at (<em class="parameter"><code>x</code></em>,\ <em class="parameter"><code>y</code></em>),
  59             width <em class="parameter"><code>width</code></em> and height <em class="parameter"><code>height</code></em>
  60             is used to define the convolution filter. If any pixels within this
  61             region are
  62             outside the window that is associated with the GL context, the
  63             values obtained for those pixels are undefined.
  64         </p><p>
  65             The pixels in the rectangle are processed
  66             exactly as if <a class="citerefentry" href="glReadPixels.xml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a> had been called with <span class="emphasis"><em>format</em></span>
  67             set to RGBA, but the process stops just before final conversion.
  68             The R, G, B, and A components of each pixel are next scaled by the four
  69             2D <code class="constant">GL_CONVOLUTION_FILTER_SCALE</code> parameters and biased by the
  70             four 2D <code class="constant">GL_CONVOLUTION_FILTER_BIAS</code> parameters.
  71             (The scale and bias parameters are set by <a class="citerefentry" href="glConvolutionParameter.xml"><span class="citerefentry"><span class="refentrytitle">glConvolutionParameter</span></span></a>
  72             using the <code class="constant">GL_CONVOLUTION_2D</code> target and the names
  73             <code class="constant">GL_CONVOLUTION_FILTER_SCALE</code> and <code class="constant">GL_CONVOLUTION_FILTER_BIAS</code>.
  74             The parameters themselves are vectors of four values that are applied to red,
  75             green, blue, and alpha, in that order.)
  76             The R, G, B, and A values are not clamped to [0,1] at any time during this
  77             process.
  78         </p><p>
  79             Each pixel is then converted to the internal format specified by
  80             <em class="parameter"><code>internalformat</code></em>.
  81             This conversion simply maps the component values of the pixel (R, G, B,
  82             and A) to the values included in the internal format (red, green, blue,
  83             alpha, luminance, and intensity).  The mapping is as follows:
  84         </p><p>
  85         </p><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>
  86                         Internal Format
  87                         </strong></span></th><th align="center"><span class="bold"><strong>
  88                         Red
  89                         </strong></span></th><th align="center"><span class="bold"><strong>
  90                         Green
  91                         </strong></span></th><th align="center"><span class="bold"><strong>
  92                         Blue
  93                         </strong></span></th><th align="center"><span class="bold"><strong>
  94                         Alpha
  95                         </strong></span></th><th align="center"><span class="bold"><strong>
  96                         Luminance
  97                         </strong></span></th><th align="center"><span class="bold"><strong>
  98                         Intensity
  99                         </strong></span></th></tr></thead><tbody><tr><td align="left">
 100                         <code class="constant">GL_ALPHA</code>
 101                         </td><td align="center">
 102                         </td><td align="center">
 103                         </td><td align="center">
 104                         </td><td align="center">
 105                         A
 106                         </td><td align="center">
 107                         </td><td align="center">
 108
 109                         </td></tr><tr><td align="left">
 110                         <code class="constant">GL_LUMINANCE</code>
 111                         </td><td align="center">
 112                         </td><td align="center">
 113                         </td><td align="center">
 114                         </td><td align="center">
 115                         </td><td align="center">
 116                         R
 117                         </td><td align="center">
 118
 119                         </td></tr><tr><td align="left">
 120                         <code class="constant">GL_LUMINANCE_ALPHA</code>
 121                         </td><td align="center">
 122                         </td><td align="center">
 123                         </td><td align="center">
 124                         </td><td align="center">
 125                         A
 126                         </td><td align="center">
 127                         R
 128                         </td><td align="center">
 129
 130                         </td></tr><tr><td align="left">
 131                         <code class="constant">GL_INTENSITY</code>
 132                         </td><td align="center">
 133                         </td><td align="center">
 134                         </td><td align="center">
 135                         </td><td align="center">
 136                         </td><td align="center">
 137                         </td><td align="center">
 138                         R
 139                         </td></tr><tr><td align="left">
 140                         <code class="constant">GL_RGB</code>
 141                         </td><td align="center">
 142                         R
 143                         </td><td align="center">
 144                         G
 145                         </td><td align="center">
 146                         B
 147                         </td><td align="center">
 148                         </td><td align="center">
 149                         </td><td align="center">
 150
 151                         </td></tr><tr><td align="left">
 152                         <code class="constant">GL_RGBA</code>
 153                         </td><td align="center">
 154                         R
 155                         </td><td align="center">
 156                         G
 157                         </td><td align="center">
 158                         B
 159                         </td><td align="center">
 160                         A
 161                         </td><td align="center">
 162                         </td><td align="center">
 163
 164                         </td></tr></tbody></table></div><p>
 165             The red, green, blue, alpha, luminance, and/or intensity components of
 166             the resulting pixels are stored in floating-point rather than integer
 167             format.
 168         </p><p>
 169             Pixel ordering is such that lower x screen coordinates correspond to
 170             lower <span class="emphasis"><em>i</em></span> filter image coordinates, and lower y screen coordinates
 171             correspond to lower <span class="emphasis"><em>j</em></span> filter image coordinates.
 172         </p><p>
 173             Note that after a convolution is performed, the resulting color
 174             components are also scaled by their corresponding
 175             <code class="constant">GL_POST_CONVOLUTION_c_SCALE</code> parameters and biased by their
 176             corresponding <code class="constant">GL_POST_CONVOLUTION_c_BIAS</code> parameters (where
 177             <span class="emphasis"><em>c</em></span> takes on the values <span class="bold"><strong>RED</strong></span>, <span class="bold"><strong>GREEN</strong></span>, <span class="bold"><strong>BLUE</strong></span>, and
 178             <span class="bold"><strong>ALPHA</strong></span>).
 179             These parameters are set by <a class="citerefentry" href="glPixelTransfer.xml"><span class="citerefentry"><span class="refentrytitle">glPixelTransfer</span></span></a>.
 180         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
 181             <code class="function">glCopyConvolutionFilter2D</code> is present only if <code class="code">ARB_imaging</code> is returned when <a class="citerefentry" href="glGetString.xml"><span class="citerefentry"><span class="refentrytitle">glGetString</span></span></a>
 182             is called with an argument of <code class="constant">GL_EXTENSIONS</code>.
 183         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 184             <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>target</code></em> is not
 185             <code class="constant">GL_CONVOLUTION_2D</code>.
 186         </p><p>
 187             <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>internalformat</code></em> is not one of the
 188             allowable values.
 189         </p><p>
 190             <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>width</code></em> is less than zero or greater
 191             than the maximum supported value.
 192             This value may be queried with <a class="citerefentry" href="glGetConvolutionParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetConvolutionParameter</span></span></a>
 193             using target <code class="constant">GL_CONVOLUTION_2D</code> and name
 194             <code class="constant">GL_MAX_CONVOLUTION_WIDTH</code>.
 195         </p><p>
 196             <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>height</code></em> is less than zero or greater
 197             than the maximum supported value.
 198             This value may be queried with <a class="citerefentry" href="glGetConvolutionParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetConvolutionParameter</span></span></a>
 199             using target <code class="constant">GL_CONVOLUTION_2D</code> and name
 200             <code class="constant">GL_MAX_CONVOLUTION_HEIGHT</code>.
 201         </p><p>
 202             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glCopyConvolutionFilter2D</code> is executed
 203             between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> and the corresponding
 204             execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 205         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 206             <a class="citerefentry" href="glGetConvolutionParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetConvolutionParameter</span></span></a>, <a class="citerefentry" href="glGetConvolutionFilter.xml"><span class="citerefentry"><span class="refentrytitle">glGetConvolutionFilter</span></span></a>
 207         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 208             <a class="citerefentry" href="glConvolutionFilter2D.xml"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter2D</span></span></a>,
 209             <a class="citerefentry" href="glConvolutionParameter.xml"><span class="citerefentry"><span class="refentrytitle">glConvolutionParameter</span></span></a>,
 210             <a class="citerefentry" href="glPixelTransfer.xml"><span class="citerefentry"><span class="refentrytitle">glPixelTransfer</span></span></a>
 211         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 212             Copyright <span class="trademark"></span>© 1991-2006
 213             Silicon Graphics, Inc. This document is licensed under the SGI
 214             Free Software B License. For details, see
 215             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 216         </p></div></div></body></html>