upstream-doc/man2/xhtml/glCopyPixels.xml

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
   2 <!-- saved from url=(0013)about:internet -->
   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>glCopyPixels</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glCopyPixels"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glCopyPixels — copy pixels in the frame buffer</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">glCopyPixels</b>(</code></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>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">type</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>x</code></em>, </span><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p>
   4                     Specify the window coordinates of the lower left corner
   5                     of the rectangular region of pixels to be copied.
   6                 </p></dd><dt><span class="term"><em class="parameter"><code>width</code></em>, </span><span class="term"><em class="parameter"><code>height</code></em></span></dt><dd><p>
   7                     Specify the dimensions of the rectangular region of pixels to be copied.
   8                     Both must be nonnegative.
   9                 </p></dd><dt><span class="term"><em class="parameter"><code>type</code></em></span></dt><dd><p>
  10                     Specifies whether color values,
  11                     depth values,
  12                     or stencil values are to be copied.
  13                     Symbolic constants
  14                     <code class="constant">GL_COLOR</code>,
  15                     <code class="constant">GL_DEPTH</code>,
  16                     and <code class="constant">GL_STENCIL</code> are accepted.
  17                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  18             <code class="function">glCopyPixels</code> copies a screen-aligned rectangle of pixels
  19             from the specified frame buffer location to a region relative to the
  20             current raster position.
  21             Its operation is well defined only if the entire pixel source region
  22             is within the exposed portion of the window.
  23             Results of copies from outside the window,
  24             or from regions of the window that are not exposed,
  25             are hardware dependent and undefined.
  26         </p><p>
  27             <em class="parameter"><code>x</code></em> and <em class="parameter"><code>y</code></em> specify the window coordinates of
  28             the lower left corner of the rectangular region to be copied.
  29             <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> specify the dimensions of the
  30             rectangular region to be copied.
  31             Both <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> must not be negative.
  32         </p><p>
  33             Several parameters control the processing of the pixel data
  34             while it is being copied.
  35             These parameters are set with three commands:
  36             <a class="citerefentry" href="glPixelTransfer.xml"><span class="citerefentry"><span class="refentrytitle">glPixelTransfer</span></span></a>,
  37             <a class="citerefentry" href="glPixelMap.xml"><span class="citerefentry"><span class="refentrytitle">glPixelMap</span></span></a>, and
  38             <a class="citerefentry" href="glPixelZoom.xml"><span class="citerefentry"><span class="refentrytitle">glPixelZoom</span></span></a>.
  39             This reference page describes the effects on <code class="function">glCopyPixels</code> of most,
  40             but not all, of the parameters specified by these three commands.
  41         </p><p>
  42             <code class="function">glCopyPixels</code> copies values from each pixel with the lower left-hand corner at
  43             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  44
  45                 <mml:mfenced open="(" close=")">
  46                     <mml:mrow>
  47                         <mml:mi mathvariant="italic">x</mml:mi>
  48                         <mml:mo>+</mml:mo>
  49                         <mml:mi mathvariant="italic">i</mml:mi>
  50                     </mml:mrow>
  51                     <mml:mrow>
  52                         <mml:mi mathvariant="italic">y</mml:mi>
  53                         <mml:mo>+</mml:mo>
  54                         <mml:mi mathvariant="italic">j</mml:mi>
  55                     </mml:mrow>
  56                 </mml:mfenced>
  57             </mml:math>
  58             for
  59             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  60
  61                 <mml:mrow>
  62                     <mml:mn>0</mml:mn>
  63                     <mml:mo>&lt;=</mml:mo>
  64                     <mml:mi mathvariant="italic">i</mml:mi>
  65                     <mml:mo>&lt;</mml:mo>
  66                     <mml:mi mathvariant="italic">width</mml:mi>
  67                 </mml:mrow>
  68             </mml:math>
  69             and
  70             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  71
  72                 <mml:mrow>
  73                     <mml:mn>0</mml:mn>
  74                     <mml:mo>&lt;=</mml:mo>
  75                     <mml:mi mathvariant="italic">j</mml:mi>
  76                     <mml:mo>&lt;</mml:mo>
  77                     <mml:mi mathvariant="italic">height</mml:mi>
  78                 </mml:mrow>
  79             </mml:math>.
  80             This pixel is said to be the
  81             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
  82             pixel in the
  83             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
  84             row.
  85             Pixels are copied in row order from the lowest to the highest row,
  86             left to right in each row.
  87         </p><p>
  88             <em class="parameter"><code>type</code></em> specifies whether color, depth, or stencil data is to be copied.
  89             The details of the transfer for each data type are as follows:
  90         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_COLOR</code></span></dt><dd><p>
  91                         Indices or RGBA colors are read from the buffer currently specified as the
  92                         read source buffer (see <a class="citerefentry" href="glReadBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a>).
  93                         If the GL is in color index mode,
  94                         each index that is read from this buffer is converted
  95                         to a fixed-point format with an unspecified
  96                         number of bits to the right of the binary point.
  97                         Each index is then shifted left by <code class="constant">GL_INDEX_SHIFT</code> bits,
  98                         and added to <code class="constant">GL_INDEX_OFFSET</code>.
  99                         If <code class="constant">GL_INDEX_SHIFT</code> is negative,
 100                         the shift is to the right.
 101                         In either case, zero bits fill otherwise unspecified bit locations in the
 102                         result.
 103                         If <code class="constant">GL_MAP_COLOR</code> is true,
 104                         the index is replaced with the value that it references in lookup table
 105                         <code class="constant">GL_PIXEL_MAP_I_TO_I</code>.
 106                         Whether the lookup replacement of the index is done or not,
 107                         the integer part of the index is then ANDed with
 108                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 109
 110                             <mml:mrow>
 111                                 <mml:msup><mml:mn>2</mml:mn>
 112                                 <mml:mi mathvariant="italic">b</mml:mi>
 113                                 </mml:msup>
 114                                 <mml:mo>-</mml:mo>
 115                                 <mml:mn>1</mml:mn>
 116                             </mml:mrow>
 117                         </mml:math>,
 118                         where
 119                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">b</mml:mi></mml:math>
 120                         is the number of bits in a color index buffer.
 121                     </p><p>
 122                         If the GL is in RGBA mode,
 123                         the red, green, blue, and alpha components of each pixel that is read
 124                         are converted to an internal floating-point format with unspecified
 125                         precision.
 126                         The conversion maps the largest representable component value to 1.0,
 127                         and component value 0 to 0.0.
 128                         The resulting floating-point color values are then multiplied
 129                         by <code class="constant">GL_c_SCALE</code> and added to <code class="constant">GL_c_BIAS</code>,
 130                         where <span class="emphasis"><em>c</em></span> is RED, GREEN, BLUE, and ALPHA
 131                         for the respective color components.
 132                         The results are clamped to the range [0,1].
 133                         If <code class="constant">GL_MAP_COLOR</code> is true,
 134                         each color component is scaled by the size of lookup table
 135                         <code class="constant">GL_PIXEL_MAP_c_TO_c</code>,
 136                         then replaced by the value that it references in that table.
 137                         <span class="emphasis"><em>c</em></span> is R, G, B, or A.
 138                     </p><p>
 139                         If the <code class="code">ARB_imaging</code> extension is supported, the color values may
 140                         be
 141                         additionally processed by color-table lookups, color-matrix
 142                         transformations, and convolution filters.
 143                     </p><p>
 144                         The GL then converts the resulting indices or RGBA colors to fragments
 145                         by attaching the current raster position <span class="emphasis"><em>z</em></span> coordinate and
 146                         texture coordinates to each pixel,
 147                         then assigning window coordinates
 148                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 149
 150                             <mml:mfenced open="(" close=")">
 151                                 <mml:mrow>
 152                                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 153                                     <mml:mi mathvariant="italic">r</mml:mi>
 154                                     </mml:msub>
 155                                     <mml:mo>+</mml:mo>
 156                                     <mml:mi mathvariant="italic">i</mml:mi>
 157                                 </mml:mrow>
 158                                 <mml:mrow>
 159                                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 160                                     <mml:mi mathvariant="italic">r</mml:mi>
 161                                     </mml:msub>
 162                                     <mml:mo>+</mml:mo>
 163                                     <mml:mi mathvariant="italic">j</mml:mi>
 164                                 </mml:mrow>
 165                             </mml:mfenced>
 166                         </mml:math>,
 167                         where
 168                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 169
 170                             <mml:mfenced open="(" close=")">
 171                                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 172                                 <mml:mi mathvariant="italic">r</mml:mi>
 173                                 </mml:msub>
 174                                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 175                                 <mml:mi mathvariant="italic">r</mml:mi>
 176                                 </mml:msub>
 177                             </mml:mfenced>
 178                         </mml:math>
 179                         is the current raster position,
 180                         and the pixel was the
 181                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
 182                         pixel in the
 183                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
 184                         row.
 185                         These pixel fragments are then treated just like the fragments generated by
 186                         rasterizing points, lines, or polygons.
 187                         Texture mapping,
 188                         fog,
 189                         and all the fragment operations are applied before the fragments are written
 190                         to the frame buffer.
 191                     </p></dd><dt><span class="term"><code class="constant">GL_DEPTH</code></span></dt><dd><p>
 192                         Depth values are read from the depth buffer and
 193                         converted directly to an internal floating-point format
 194                         with unspecified precision.
 195                         The resulting floating-point depth value is then multiplied
 196                         by <code class="constant">GL_DEPTH_SCALE</code> and added to <code class="constant">GL_DEPTH_BIAS</code>.
 197                         The result is clamped to the range [0,1].
 198                     </p><p>
 199                         The GL then converts the resulting depth components to fragments
 200                         by attaching the current raster position color or color index and
 201                         texture coordinates to each pixel,
 202                         then assigning window coordinates
 203                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 204
 205                             <mml:mfenced open="(" close=")">
 206                                 <mml:mrow>
 207                                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 208                                     <mml:mi mathvariant="italic">r</mml:mi>
 209                                     </mml:msub>
 210                                     <mml:mo>+</mml:mo>
 211                                     <mml:mi mathvariant="italic">i</mml:mi>
 212                                 </mml:mrow>
 213                                 <mml:mrow>
 214                                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 215                                     <mml:mi mathvariant="italic">r</mml:mi>
 216                                     </mml:msub>
 217                                     <mml:mo>+</mml:mo>
 218                                     <mml:mi mathvariant="italic">j</mml:mi>
 219                                 </mml:mrow>
 220                             </mml:mfenced>
 221                         </mml:math>,
 222                         where
 223                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 224
 225                             <mml:mfenced open="(" close=")">
 226                                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 227                                 <mml:mi mathvariant="italic">r</mml:mi>
 228                                 </mml:msub>
 229                                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 230                                 <mml:mi mathvariant="italic">r</mml:mi>
 231                                 </mml:msub>
 232                             </mml:mfenced>
 233                         </mml:math>
 234                         is the current raster position,
 235                         and the pixel was the
 236                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
 237                         pixel in the
 238                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
 239                         row.
 240                         These pixel fragments are then treated just like the fragments generated by
 241                         rasterizing points, lines, or polygons.
 242                         Texture mapping,
 243                         fog,
 244                         and all the fragment operations are applied before the fragments are written
 245                         to the frame buffer.
 246                     </p></dd><dt><span class="term"><code class="constant">GL_STENCIL</code></span></dt><dd><p>
 247                         Stencil indices are read from the stencil buffer and
 248                         converted to an internal fixed-point format
 249                         with an unspecified number of bits to the right of the binary point.
 250                         Each fixed-point index is then shifted left by <code class="constant">GL_INDEX_SHIFT</code> bits,
 251                         and added to <code class="constant">GL_INDEX_OFFSET</code>.
 252                         If <code class="constant">GL_INDEX_SHIFT</code> is negative,
 253                         the shift is to the right.
 254                         In either case, zero bits fill otherwise unspecified bit locations in the
 255                         result.
 256                         If <code class="constant">GL_MAP_STENCIL</code> is true,
 257                         the index is replaced with the value that it references in lookup table
 258                         <code class="constant">GL_PIXEL_MAP_S_TO_S</code>.
 259                         Whether the lookup replacement of the index is done or not,
 260                         the integer part of the index is then ANDed with
 261                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 262
 263                             <mml:mrow>
 264                                 <mml:msup><mml:mn>2</mml:mn>
 265                                 <mml:mi mathvariant="italic">b</mml:mi>
 266                                 </mml:msup>
 267                                 <mml:mo>-</mml:mo>
 268                                 <mml:mn>1</mml:mn>
 269                             </mml:mrow>
 270                         </mml:math>,
 271                         where
 272                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">b</mml:mi></mml:math>
 273                         is the number of bits in the stencil buffer.
 274                         The resulting stencil indices are then written to the stencil buffer
 275                         such that the index read from the
 276                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
 277                         location of the
 278                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
 279                         row
 280                         is written to location
 281                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 282
 283                             <mml:mfenced open="(" close=")">
 284                                 <mml:mrow>
 285                                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 286                                     <mml:mi mathvariant="italic">r</mml:mi>
 287                                     </mml:msub>
 288                                     <mml:mo>+</mml:mo>
 289                                     <mml:mi mathvariant="italic">i</mml:mi>
 290                                 </mml:mrow>
 291                                 <mml:mrow>
 292                                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 293                                     <mml:mi mathvariant="italic">r</mml:mi>
 294                                     </mml:msub>
 295                                     <mml:mo>+</mml:mo>
 296                                     <mml:mi mathvariant="italic">j</mml:mi>
 297                                 </mml:mrow>
 298                             </mml:mfenced>
 299                         </mml:math>,
 300                         where
 301                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 302
 303                             <mml:mfenced open="(" close=")">
 304                                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 305                                 <mml:mi mathvariant="italic">r</mml:mi>
 306                                 </mml:msub>
 307                                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 308                                 <mml:mi mathvariant="italic">r</mml:mi>
 309                                 </mml:msub>
 310                             </mml:mfenced>
 311                         </mml:math>
 312                         is the current raster position.
 313                         Only the pixel ownership test,
 314                         the scissor test,
 315                         and the stencil writemask affect these write operations.
 316                     </p></dd></dl></div><p>
 317             The rasterization described thus far assumes pixel zoom factors of 1.0.
 318             If
 319             <a class="citerefentry" href="glPixelZoom.xml"><span class="citerefentry"><span class="refentrytitle">glPixelZoom</span></span></a> is used to change the
 320             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math>
 321             and
 322             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math>
 323             pixel zoom factors,
 324             pixels are converted to fragments as follows.
 325             If
 326             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 327
 328                 <mml:mfenced open="(" close=")">
 329                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 330                     <mml:mi mathvariant="italic">r</mml:mi>
 331                     </mml:msub>
 332                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 333                     <mml:mi mathvariant="italic">r</mml:mi>
 334                     </mml:msub>
 335                 </mml:mfenced>
 336             </mml:math>
 337             is the current raster position,
 338             and a given pixel is in the
 339             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
 340             location in the
 341             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
 342             row of the source
 343             pixel rectangle,
 344             then fragments are generated for pixels whose centers are in the rectangle
 345             with corners at
 346         </p><p>
 347             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 348
 349                 <mml:mfenced open="(" close=")">
 350                     <mml:mrow>
 351                         <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 352                         <mml:mi mathvariant="italic">r</mml:mi>
 353                         </mml:msub>
 354                         <mml:mo>+</mml:mo>
 355                         <mml:mfenced open="" close="">
 356                             <mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
 357                             <mml:mi mathvariant="italic">x</mml:mi>
 358                             </mml:msub>
 359                         </mml:mfenced>
 360                         <mml:mo>⁢</mml:mo>
 361                         <mml:mi mathvariant="italic">i</mml:mi>
 362                     </mml:mrow>
 363                     <mml:mrow>
 364                         <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 365                         <mml:mi mathvariant="italic">r</mml:mi>
 366                         </mml:msub>
 367                         <mml:mo>+</mml:mo>
 368                         <mml:mfenced open="" close="">
 369                             <mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
 370                             <mml:mi mathvariant="italic">y</mml:mi>
 371                             </mml:msub>
 372                         </mml:mfenced>
 373                         <mml:mo>⁢</mml:mo>
 374                         <mml:mi mathvariant="italic">j</mml:mi>
 375                     </mml:mrow>
 376                 </mml:mfenced>
 377             </mml:math>
 378         </p><p>
 379              and
 380         </p><p>
 381             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 382
 383                 <mml:mfenced open="(" close=")">
 384                     <mml:mrow>
 385                         <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
 386                         <mml:mi mathvariant="italic">r</mml:mi>
 387                         </mml:msub>
 388                         <mml:mo>+</mml:mo>
 389                         <mml:mrow>
 390                             <mml:mfenced open="" close="">
 391                                 <mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
 392                                 <mml:mi mathvariant="italic">x</mml:mi>
 393                                 </mml:msub>
 394                             </mml:mfenced>
 395                             <mml:mo>⁡</mml:mo>
 396                             <mml:mfenced open="(" close=")">
 397                                 <mml:mrow>
 398                                     <mml:mi mathvariant="italic">i</mml:mi>
 399                                     <mml:mo>+</mml:mo>
 400                                     <mml:mn>1</mml:mn>
 401                                 </mml:mrow>
 402                             </mml:mfenced>
 403                         </mml:mrow>
 404                     </mml:mrow>
 405                     <mml:mrow>
 406                         <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
 407                         <mml:mi mathvariant="italic">r</mml:mi>
 408                         </mml:msub>
 409                         <mml:mo>+</mml:mo>
 410                         <mml:mrow>
 411                             <mml:mfenced open="" close="">
 412                                 <mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
 413                                 <mml:mi mathvariant="italic">y</mml:mi>
 414                                 </mml:msub>
 415                             </mml:mfenced>
 416                             <mml:mo>⁡</mml:mo>
 417                             <mml:mfenced open="(" close=")">
 418                                 <mml:mrow>
 419                                     <mml:mi mathvariant="italic">j</mml:mi>
 420                                     <mml:mo>+</mml:mo>
 421                                     <mml:mn>1</mml:mn>
 422                                 </mml:mrow>
 423                             </mml:mfenced>
 424                         </mml:mrow>
 425                     </mml:mrow>
 426                 </mml:mfenced>
 427             </mml:math>
 428         </p><p>
 429             where
 430             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 431
 432                 <mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
 433                 <mml:mi mathvariant="italic">x</mml:mi>
 434                 </mml:msub>
 435             </mml:math>
 436             is the value of <code class="constant">GL_ZOOM_X</code> and
 437             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 438
 439                 <mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
 440                 <mml:mi mathvariant="italic">y</mml:mi>
 441                 </mml:msub>
 442             </mml:math>
 443             is the value of <code class="constant">GL_ZOOM_Y</code>.
 444         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="examples"></a><h2>Examples</h2><p>
 445             To copy the color pixel in the lower left corner of the window to the current raster position,
 446             use
 447         </p><p>
 448             </p><pre class="programlisting">
 449 glCopyPixels(0, 0, 1, 1, <code class="constant">GL_COLOR</code>);
 450             </pre><p>
 451         </p><p>
 452         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
 453             Modes specified by <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a> have no effect on the operation
 454             of <code class="function">glCopyPixels</code>.
 455         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 456             <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>type</code></em> is not an accepted value.
 457         </p><p>
 458             <code class="constant">GL_INVALID_VALUE</code> is generated if either <em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em> is negative.
 459         </p><p>
 460             <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>type</code></em> is <code class="constant">GL_DEPTH</code>
 461             and there is no depth buffer.
 462         </p><p>
 463             <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>type</code></em> is <code class="constant">GL_STENCIL</code>
 464             and there is no stencil buffer.
 465         </p><p>
 466             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glCopyPixels</code>
 467             is executed between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
 468             and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 469         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 470             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_CURRENT_RASTER_POSITION</code>
 471         </p><p>
 472             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_CURRENT_RASTER_POSITION_VALID</code>
 473         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 474             <a class="citerefentry" href="glColorTable.xml"><span class="citerefentry"><span class="refentrytitle">glColorTable</span></span></a>,
 475             <a class="citerefentry" href="glConvolutionFilter1D.xml"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter1D</span></span></a>,
 476             <a class="citerefentry" href="glConvolutionFilter2D.xml"><span class="citerefentry"><span class="refentrytitle">glConvolutionFilter2D</span></span></a>,
 477             <a class="citerefentry" href="glDepthFunc.xml"><span class="citerefentry"><span class="refentrytitle">glDepthFunc</span></span></a>,
 478             <a class="citerefentry" href="glDrawBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>,
 479             <a class="citerefentry" href="glDrawPixels.xml"><span class="citerefentry"><span class="refentrytitle">glDrawPixels</span></span></a>,
 480             <a class="citerefentry" href="glMatrixMode.xml"><span class="citerefentry"><span class="refentrytitle">glMatrixMode</span></span></a>,
 481             <a class="citerefentry" href="glPixelMap.xml"><span class="citerefentry"><span class="refentrytitle">glPixelMap</span></span></a>,
 482             <a class="citerefentry" href="glPixelTransfer.xml"><span class="citerefentry"><span class="refentrytitle">glPixelTransfer</span></span></a>,
 483             <a class="citerefentry" href="glPixelZoom.xml"><span class="citerefentry"><span class="refentrytitle">glPixelZoom</span></span></a>,
 484             <a class="citerefentry" href="glRasterPos.xml"><span class="citerefentry"><span class="refentrytitle">glRasterPos</span></span></a>,
 485             <a class="citerefentry" href="glReadBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a>,
 486             <a class="citerefentry" href="glReadPixels.xml"><span class="citerefentry"><span class="refentrytitle">glReadPixels</span></span></a>,
 487             <a class="citerefentry" href="glSeparableFilter2D.xml"><span class="citerefentry"><span class="refentrytitle">glSeparableFilter2D</span></span></a>,
 488             <a class="citerefentry" href="glStencilFunc.xml"><span class="citerefentry"><span class="refentrytitle">glStencilFunc</span></span></a>,
 489             <a class="citerefentry" href="glWindowPos.xml"><span class="citerefentry"><span class="refentrytitle">glWindowPos</span></span></a>
 490         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 491             Copyright <span class="trademark"></span>© 1991-2006
 492             Silicon Graphics, Inc. This document is licensed under the SGI
 493             Free Software B License. For details, see
 494             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 495         </p></div></div></body></html>