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AW		 1<?xml version="1.0" encoding="UTF-8"?>
2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
3<!-- saved from url=(0013)about:internet -->
4<?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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glReadPixels</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /></head><body><div class="refentry" title="glReadPixels"><a id="glReadPixels"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glReadPixels — read a block of pixels from the frame buffer</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glReadPixels</b>(</code></td><td>GLint <var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">height</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">format</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">type</var>, </td></tr><tr><td> </td><td>GLvoid * <var class="pdparam">data</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><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>
5 Specify the window coordinates of the first pixel
6 that is read from the frame buffer.
7 This location is the lower left corner of a rectangular block of pixels.
8 </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>
9 Specify the dimensions of the pixel rectangle.
10 <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> of one correspond to a single pixel.
11 </p></dd><dt><span class="term"><em class="parameter"><code>format</code></em></span></dt><dd><p>
12 Specifies the format of the pixel data.
13 The following symbolic values are accepted:
14 <code class="constant">GL_STENCIL_INDEX</code>,
15 <code class="constant">GL_DEPTH_COMPONENT</code>,
16 <code class="constant">GL_DEPTH_STENCIL</code>,
17 <code class="constant">GL_RED</code>,
18 <code class="constant">GL_GREEN</code>,
19 <code class="constant">GL_BLUE</code>,
20 <code class="constant">GL_RGB</code>,
21 <code class="constant">GL_BGR</code>,
22 <code class="constant">GL_RGBA</code>, and
23 <code class="constant">GL_BGRA</code>.
24 </p></dd><dt><span class="term"><em class="parameter"><code>type</code></em></span></dt><dd><p>
25 Specifies the data type of the pixel data.
26 Must be one of
27 <code class="constant">GL_UNSIGNED_BYTE</code>,
28 <code class="constant">GL_BYTE</code>,
29 <code class="constant">GL_UNSIGNED_SHORT</code>,
30 <code class="constant">GL_SHORT</code>,
31 <code class="constant">GL_UNSIGNED_INT</code>,
32 <code class="constant">GL_INT</code>,
33 <code class="constant">GL_HALF_FLOAT</code>,
34 <code class="constant">GL_FLOAT</code>,
35 <code class="constant">GL_UNSIGNED_BYTE_3_3_2</code>,
36 <code class="constant">GL_UNSIGNED_BYTE_2_3_3_REV</code>,
37 <code class="constant">GL_UNSIGNED_SHORT_5_6_5</code>,
38 <code class="constant">GL_UNSIGNED_SHORT_5_6_5_REV</code>,
39 <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4</code>,
40 <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4_REV</code>,
41 <code class="constant">GL_UNSIGNED_SHORT_5_5_5_1</code>,
42 <code class="constant">GL_UNSIGNED_SHORT_1_5_5_5_REV</code>,
43 <code class="constant">GL_UNSIGNED_INT_8_8_8_8</code>,
44 <code class="constant">GL_UNSIGNED_INT_8_8_8_8_REV</code>,
45 <code class="constant">GL_UNSIGNED_INT_10_10_10_2</code>,
46 <code class="constant">GL_UNSIGNED_INT_2_10_10_10_REV</code>,
47 <code class="constant">GL_UNSIGNED_INT_24_8</code>,
48 <code class="constant">GL_UNSIGNED_INT_10F_11F_11F_REV</code>,
49 <code class="constant">GL_UNSIGNED_INT_5_9_9_9_REV</code>, or
50 <code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>.
51 </p></dd><dt><span class="term"><em class="parameter"><code>data</code></em></span></dt><dd><p>
52 Returns the pixel data.
53 </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>
54 <code class="function">glReadPixels</code> returns pixel data from the frame buffer,
55 starting with the pixel whose lower left corner
56 is at location (<em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em>),
57 into client memory starting at location <em class="parameter"><code>data</code></em>.
58 Several parameters control the processing of the pixel data before
59 it is placed into client memory.
60 These parameters are set with <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>.
61 This reference page describes the effects on <code class="function">glReadPixels</code> of most,
62 but not all of the parameters specified by these three commands.
63 </p><p>
64 If a non-zero named buffer object is bound to the <code class="constant">GL_PIXEL_PACK_BUFFER</code> target
65 (see <a class="citerefentry" href="glBindBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glBindBuffer</span></span></a>) while a block of pixels is
66 requested, <em class="parameter"><code>data</code></em> is treated as a byte offset into the buffer object's data store
67 rather than a pointer to client memory.
68 </p><p>
69 <code class="function">glReadPixels</code> returns values from each pixel with lower left corner at
70 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
71
72 <mml:mfenced open="(" close=")">
73 <mml:mrow>
74 <mml:mi mathvariant="italic">x</mml:mi>
75 <mml:mo>+</mml:mo>
76 <mml:mi mathvariant="italic">i</mml:mi>
77 </mml:mrow>
78 <mml:mrow>
79 <mml:mi mathvariant="italic">y</mml:mi>
80 <mml:mo>+</mml:mo>
81 <mml:mi mathvariant="italic">j</mml:mi>
82 </mml:mrow>
83 </mml:mfenced>
84 </mml:math>
85 for
86 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
87
88 <mml:mrow>
89 <mml:mn>0</mml:mn>
90 <mml:mo>&lt;=</mml:mo>
91 <mml:mi mathvariant="italic">i</mml:mi>
92 <mml:mo>&lt;</mml:mo>
93 <mml:mi mathvariant="italic">width</mml:mi>
94 </mml:mrow>
95 </mml:math>
96 and
97 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
98
99 <mml:mrow>
100 <mml:mn>0</mml:mn>
101 <mml:mo>&lt;=</mml:mo>
102 <mml:mi mathvariant="italic">j</mml:mi>
103 <mml:mo>&lt;</mml:mo>
104 <mml:mi mathvariant="italic">height</mml:mi>
105 </mml:mrow>
106 </mml:math>.
107 This pixel is said to be the
108 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
109 pixel in the
110 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
111 row.
112 Pixels are returned in row order from the lowest to the highest row,
113 left to right in each row.
114 </p><p>
115 <em class="parameter"><code>format</code></em> specifies the format for the returned pixel values;
116 accepted values are:
117 </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_STENCIL_INDEX</code></span></dt><dd><p>
118 Stencil values are read from the stencil buffer.
119 Each index is converted to fixed point,
120 shifted left or right depending on the value and sign of <code class="constant">GL_INDEX_SHIFT</code>,
121 and added to <code class="constant">GL_INDEX_OFFSET</code>.
122 If <code class="constant">GL_MAP_STENCIL</code> is <code class="constant">GL_TRUE</code>,
123 indices are replaced by their mappings in the table <code class="constant">GL_PIXEL_MAP_S_TO_S</code>.
124 </p></dd><dt><span class="term"><code class="constant">GL_DEPTH_COMPONENT</code></span></dt><dd><p>
125 Depth values are read from the depth buffer.
126 Each component is converted to floating point such that the minimum depth
127 value maps to 0 and the maximum value maps to 1.
128 Each component is then multiplied by <code class="constant">GL_DEPTH_SCALE</code>,
129 added to <code class="constant">GL_DEPTH_BIAS</code>,
130 and finally clamped to the range
131 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
132
133 <mml:mfenced open="[" close="]">
134 <mml:mn>0</mml:mn>
135 <mml:mn>1</mml:mn>
136 </mml:mfenced>
137 </mml:math>.
138 </p></dd><dt><span class="term"><code class="constant">GL_DEPTH_STENCIL</code></span></dt><dd><p>
139 Values are taken from both the depth and stencil buffers. The <em class="parameter"><code>type</code></em> parameter
140 must be <code class="constant">GL_UNSIGNED_INT_24_8</code> or <code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>.
141 </p></dd><dt><span class="term"><code class="constant">GL_RED</code></span></dt><dd></dd><dt><span class="term"><code class="constant">GL_GREEN</code></span></dt><dd></dd><dt><span class="term"><code class="constant">GL_BLUE</code></span></dt><dd></dd><dt><span class="term"><code class="constant">GL_RGB</code></span></dt><dd></dd><dt><span class="term"><code class="constant">GL_BGR</code></span></dt><dd></dd><dt><span class="term"><code class="constant">GL_RGBA</code></span></dt><dd></dd><dt><span class="term"><code class="constant">GL_BGRA</code></span></dt><dd></dd></dl></div><p>
142 Finally, the indices or components
143 are converted to the proper format,
144 as specified by <em class="parameter"><code>type</code></em>.
145 If <em class="parameter"><code>format</code></em> is <code class="constant">GL_STENCIL_INDEX</code>
146 and <em class="parameter"><code>type</code></em> is not <code class="constant">GL_FLOAT</code>,
147 each index is masked with the mask value given in the following table.
148 If <em class="parameter"><code>type</code></em> is <code class="constant">GL_FLOAT</code>, then each integer index is converted to
149 single-precision floating-point format.
150 </p><p>
151 If <em class="parameter"><code>format</code></em> is
152 <code class="constant">GL_RED</code>,
153 <code class="constant">GL_GREEN</code>,
154 <code class="constant">GL_BLUE</code>,
155 <code class="constant">GL_RGB</code>,
156 <code class="constant">GL_BGR</code>,
157 <code class="constant">GL_RGBA</code>, or
158 <code class="constant">GL_BGRA</code> and <em class="parameter"><code>type</code></em> is not <code class="constant">GL_FLOAT</code>,
159 each component is multiplied by the multiplier shown in the following table.
160 If type is <code class="constant">GL_FLOAT</code>, then each component is passed as is
161 (or converted to the client's single-precision floating-point format if
162 it is different from the one used by the GL).
163 </p><p>
164 </p><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /><col align="center" /></colgroup><thead><tr><th align="left">
165 <em class="parameter"><code>type</code></em>
166 </th><th align="center"><span class="bold"><strong>
167 Index Mask
168 </strong></span></th><th align="center"><span class="bold"><strong>
169 Component Conversion
170 </strong></span></th></tr></thead><tbody><tr><td align="left">
171 <code class="constant">GL_UNSIGNED_BYTE</code>
172 </td><td align="center">
173 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
174
175 <mml:mrow>
176 <mml:msup><mml:mn>2</mml:mn>
177 <mml:mn>8</mml:mn>
178 </mml:msup>
179 <mml:mo>-</mml:mo>
180 <mml:mn>1</mml:mn>
181 </mml:mrow>
182 </mml:math>
183 </td><td align="center">
184 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
185
186 <mml:mrow>
187 <mml:mfenced open="(" close=")">
188 <mml:mrow>
189 <mml:msup><mml:mn>2</mml:mn>
190 <mml:mn>8</mml:mn>
191 </mml:msup>
192 <mml:mo>-</mml:mo>
193 <mml:mn>1</mml:mn>
194 </mml:mrow>
195 </mml:mfenced>
196 <mml:mo>⁢</mml:mo>
197 <mml:mi mathvariant="italic">c</mml:mi>
198 </mml:mrow>
199 </mml:math>
200 </td></tr><tr><td align="left">
201 <code class="constant">GL_BYTE</code>
202 </td><td align="center">
203 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
204
205 <mml:mrow>
206 <mml:msup><mml:mn>2</mml:mn>
207 <mml:mn>7</mml:mn>
208 </mml:msup>
209 <mml:mo>-</mml:mo>
210 <mml:mn>1</mml:mn>
211 </mml:mrow>
212 </mml:math>
213 </td><td align="center">
214 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
215
216 <mml:mfrac>
217 <mml:mfenced open="" close="">
218 <mml:mrow>
219 <mml:mfenced open="(" close=")">
220 <mml:mrow>
221 <mml:msup><mml:mn>2</mml:mn>
222 <mml:mn>8</mml:mn>
223 </mml:msup>
224 <mml:mo>-</mml:mo>
225 <mml:mn>1</mml:mn>
226 </mml:mrow>
227 </mml:mfenced>
228 <mml:mo>⁢</mml:mo>
229 <mml:mi mathvariant="italic">c</mml:mi>
230 <mml:mo>-</mml:mo>
231 <mml:mn>1</mml:mn>
232 </mml:mrow>
233 </mml:mfenced>
234 <mml:mn>2</mml:mn>
235 </mml:mfrac>
236 </mml:math>
237 </td></tr><tr><td align="left">
238 <code class="constant">GL_UNSIGNED_SHORT</code>
239 </td><td align="center">
240 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
241
242 <mml:mrow>
243 <mml:msup><mml:mn>2</mml:mn>
244 <mml:mn>16</mml:mn>
245 </mml:msup>
246 <mml:mo>-</mml:mo>
247 <mml:mn>1</mml:mn>
248 </mml:mrow>
249 </mml:math>
250 </td><td align="center">
251 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
252
253 <mml:mrow>
254 <mml:mfenced open="(" close=")">
255 <mml:mrow>
256 <mml:msup><mml:mn>2</mml:mn>
257 <mml:mn>16</mml:mn>
258 </mml:msup>
259 <mml:mo>-</mml:mo>
260 <mml:mn>1</mml:mn>
261 </mml:mrow>
262 </mml:mfenced>
263 <mml:mo>⁢</mml:mo>
264 <mml:mi mathvariant="italic">c</mml:mi>
265 </mml:mrow>
266 </mml:math>
267 </td></tr><tr><td align="left">
268 <code class="constant">GL_SHORT</code>
269 </td><td align="center">
270 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
271
272 <mml:mrow>
273 <mml:msup><mml:mn>2</mml:mn>
274 <mml:mn>15</mml:mn>
275 </mml:msup>
276 <mml:mo>-</mml:mo>
277 <mml:mn>1</mml:mn>
278 </mml:mrow>
279 </mml:math>
280 </td><td align="center">
281 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
282
283 <mml:mfrac>
284 <mml:mfenced open="" close="">
285 <mml:mrow>
286 <mml:mfenced open="(" close=")">
287 <mml:mrow>
288 <mml:msup><mml:mn>2</mml:mn>
289 <mml:mn>16</mml:mn>
290 </mml:msup>
291 <mml:mo>-</mml:mo>
292 <mml:mn>1</mml:mn>
293 </mml:mrow>
294 </mml:mfenced>
295 <mml:mo>⁢</mml:mo>
296 <mml:mi mathvariant="italic">c</mml:mi>
297 <mml:mo>-</mml:mo>
298 <mml:mn>1</mml:mn>
299 </mml:mrow>
300 </mml:mfenced>
301 <mml:mn>2</mml:mn>
302 </mml:mfrac>
303 </mml:math>
304 </td></tr><tr><td align="left">
305 <code class="constant">GL_UNSIGNED_INT</code>
306 </td><td align="center">
307 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
308
309 <mml:mrow>
310 <mml:msup><mml:mn>2</mml:mn>
311 <mml:mn>32</mml:mn>
312 </mml:msup>
313 <mml:mo>-</mml:mo>
314 <mml:mn>1</mml:mn>
315 </mml:mrow>
316 </mml:math>
317 </td><td align="center">
318 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
319
320 <mml:mrow>
321 <mml:mfenced open="(" close=")">
322 <mml:mrow>
323 <mml:msup><mml:mn>2</mml:mn>
324 <mml:mn>32</mml:mn>
325 </mml:msup>
326 <mml:mo>-</mml:mo>
327 <mml:mn>1</mml:mn>
328 </mml:mrow>
329 </mml:mfenced>
330 <mml:mo>⁢</mml:mo>
331 <mml:mi mathvariant="italic">c</mml:mi>
332 </mml:mrow>
333 </mml:math>
334 </td></tr><tr><td align="left">
335 <code class="constant">GL_INT</code>
336 </td><td align="center">
337 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
338
339 <mml:mrow>
340 <mml:msup><mml:mn>2</mml:mn>
341 <mml:mn>31</mml:mn>
342 </mml:msup>
343 <mml:mo>-</mml:mo>
344 <mml:mn>1</mml:mn>
345 </mml:mrow>
346 </mml:math>
347 </td><td align="center">
348 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
349
350 <mml:mfrac>
351 <mml:mfenced open="" close="">
352 <mml:mrow>
353 <mml:mfenced open="(" close=")">
354 <mml:mrow>
355 <mml:msup><mml:mn>2</mml:mn>
356 <mml:mn>32</mml:mn>
357 </mml:msup>
358 <mml:mo>-</mml:mo>
359 <mml:mn>1</mml:mn>
360 </mml:mrow>
361 </mml:mfenced>
362 <mml:mo>⁢</mml:mo>
363 <mml:mi mathvariant="italic">c</mml:mi>
364 <mml:mo>-</mml:mo>
365 <mml:mn>1</mml:mn>
366 </mml:mrow>
367 </mml:mfenced>
368 <mml:mn>2</mml:mn>
369 </mml:mfrac>
370 </mml:math>
371 </td></tr><tr><td align="left">
372 <code class="constant">GL_HALF_FLOAT</code>
373 </td><td align="center">
374 none
375 </td><td align="center">
376 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">c</mml:mi></mml:math>
377 </td></tr><tr><td align="left">
378 <code class="constant">GL_FLOAT</code>
379 </td><td align="center">
380 none
381 </td><td align="center">
382 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">c</mml:mi></mml:math>
383 </td></tr><tr><td align="left">
384 <code class="constant">GL_UNSIGNED_BYTE_3_3_2</code>
385 </td><td align="center">
386 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
387
388 <mml:mrow>
389 <mml:msup><mml:mn>2</mml:mn>
390 <mml:mn>N</mml:mn>
391 </mml:msup>
392 <mml:mo>-</mml:mo>
393 <mml:mn>1</mml:mn>
394 </mml:mrow>
395 </mml:math>
396 </td><td align="center">
397 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
398
399 <mml:mrow>
400 <mml:mfenced open="(" close=")">
401 <mml:mrow>
402 <mml:msup><mml:mn>2</mml:mn>
403 <mml:mn>N</mml:mn>
404 </mml:msup>
405 <mml:mo>-</mml:mo>
406 <mml:mn>1</mml:mn>
407 </mml:mrow>
408 </mml:mfenced>
409 <mml:mo>⁢</mml:mo>
410 <mml:mi mathvariant="italic">c</mml:mi>
411 </mml:mrow>
412 </mml:math>
413 </td></tr><tr><td align="left">
414 <code class="constant">GL_UNSIGNED_BYTE_2_3_3_REV</code>
415 </td><td align="center">
416 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
417
418 <mml:mrow>
419 <mml:msup><mml:mn>2</mml:mn>
420 <mml:mn>N</mml:mn>
421 </mml:msup>
422 <mml:mo>-</mml:mo>
423 <mml:mn>1</mml:mn>
424 </mml:mrow>
425 </mml:math>
426 </td><td align="center">
427 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
428
429 <mml:mrow>
430 <mml:mfenced open="(" close=")">
431 <mml:mrow>
432 <mml:msup><mml:mn>2</mml:mn>
433 <mml:mn>N</mml:mn>
434 </mml:msup>
435 <mml:mo>-</mml:mo>
436 <mml:mn>1</mml:mn>
437 </mml:mrow>
438 </mml:mfenced>
439 <mml:mo>⁢</mml:mo>
440 <mml:mi mathvariant="italic">c</mml:mi>
441 </mml:mrow>
442 </mml:math>
443 </td></tr><tr><td align="left">
444 <code class="constant">GL_UNSIGNED_SHORT_5_6_5</code>
445 </td><td align="center">
446 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
447
448 <mml:mrow>
449 <mml:msup><mml:mn>2</mml:mn>
450 <mml:mn>N</mml:mn>
451 </mml:msup>
452 <mml:mo>-</mml:mo>
453 <mml:mn>1</mml:mn>
454 </mml:mrow>
455 </mml:math>
456 </td><td align="center">
457 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
458
459 <mml:mrow>
460 <mml:mfenced open="(" close=")">
461 <mml:mrow>
462 <mml:msup><mml:mn>2</mml:mn>
463 <mml:mn>N</mml:mn>
464 </mml:msup>
465 <mml:mo>-</mml:mo>
466 <mml:mn>1</mml:mn>
467 </mml:mrow>
468 </mml:mfenced>
469 <mml:mo>⁢</mml:mo>
470 <mml:mi mathvariant="italic">c</mml:mi>
471 </mml:mrow>
472 </mml:math>
473 </td></tr><tr><td align="left">
474 <code class="constant">GL_UNSIGNED_SHORT_5_6_5_REV</code>
475 </td><td align="center">
476 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
477
478 <mml:mrow>
479 <mml:msup><mml:mn>2</mml:mn>
480 <mml:mn>N</mml:mn>
481 </mml:msup>
482 <mml:mo>-</mml:mo>
483 <mml:mn>1</mml:mn>
484 </mml:mrow>
485 </mml:math>
486 </td><td align="center">
487 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
488
489 <mml:mrow>
490 <mml:mfenced open="(" close=")">
491 <mml:mrow>
492 <mml:msup><mml:mn>2</mml:mn>
493 <mml:mn>N</mml:mn>
494 </mml:msup>
495 <mml:mo>-</mml:mo>
496 <mml:mn>1</mml:mn>
497 </mml:mrow>
498 </mml:mfenced>
499 <mml:mo>⁢</mml:mo>
500 <mml:mi mathvariant="italic">c</mml:mi>
501 </mml:mrow>
502 </mml:math>
503 </td></tr><tr><td align="left">
504 <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4</code>
505 </td><td align="center">
506 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
507
508 <mml:mrow>
509 <mml:msup><mml:mn>2</mml:mn>
510 <mml:mn>N</mml:mn>
511 </mml:msup>
512 <mml:mo>-</mml:mo>
513 <mml:mn>1</mml:mn>
514 </mml:mrow>
515 </mml:math>
516 </td><td align="center">
517 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
518
519 <mml:mrow>
520 <mml:mfenced open="(" close=")">
521 <mml:mrow>
522 <mml:msup><mml:mn>2</mml:mn>
523 <mml:mn>N</mml:mn>
524 </mml:msup>
525 <mml:mo>-</mml:mo>
526 <mml:mn>1</mml:mn>
527 </mml:mrow>
528 </mml:mfenced>
529 <mml:mo>⁢</mml:mo>
530 <mml:mi mathvariant="italic">c</mml:mi>
531 </mml:mrow>
532 </mml:math>
533 </td></tr><tr><td align="left">
534 <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4_REV</code>
535 </td><td align="center">
536 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
537
538 <mml:mrow>
539 <mml:msup><mml:mn>2</mml:mn>
540 <mml:mn>N</mml:mn>
541 </mml:msup>
542 <mml:mo>-</mml:mo>
543 <mml:mn>1</mml:mn>
544 </mml:mrow>
545 </mml:math>
546 </td><td align="center">
547 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
548
549 <mml:mrow>
550 <mml:mfenced open="(" close=")">
551 <mml:mrow>
552 <mml:msup><mml:mn>2</mml:mn>
553 <mml:mn>N</mml:mn>
554 </mml:msup>
555 <mml:mo>-</mml:mo>
556 <mml:mn>1</mml:mn>
557 </mml:mrow>
558 </mml:mfenced>
559 <mml:mo>⁢</mml:mo>
560 <mml:mi mathvariant="italic">c</mml:mi>
561 </mml:mrow>
562 </mml:math>
563 </td></tr><tr><td align="left">
564 <code class="constant">GL_UNSIGNED_SHORT_5_5_5_1</code>
565 </td><td align="center">
566 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
567
568 <mml:mrow>
569 <mml:msup><mml:mn>2</mml:mn>
570 <mml:mn>N</mml:mn>
571 </mml:msup>
572 <mml:mo>-</mml:mo>
573 <mml:mn>1</mml:mn>
574 </mml:mrow>
575 </mml:math>
576 </td><td align="center">
577 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
578
579 <mml:mrow>
580 <mml:mfenced open="(" close=")">
581 <mml:mrow>
582 <mml:msup><mml:mn>2</mml:mn>
583 <mml:mn>N</mml:mn>
584 </mml:msup>
585 <mml:mo>-</mml:mo>
586 <mml:mn>1</mml:mn>
587 </mml:mrow>
588 </mml:mfenced>
589 <mml:mo>⁢</mml:mo>
590 <mml:mi mathvariant="italic">c</mml:mi>
591 </mml:mrow>
592 </mml:math>
593 </td></tr><tr><td align="left">
594 <code class="constant">GL_UNSIGNED_SHORT_1_5_5_5_REV</code>
595 </td><td align="center">
596 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
597
598 <mml:mrow>
599 <mml:msup><mml:mn>2</mml:mn>
600 <mml:mn>N</mml:mn>
601 </mml:msup>
602 <mml:mo>-</mml:mo>
603 <mml:mn>1</mml:mn>
604 </mml:mrow>
605 </mml:math>
606 </td><td align="center">
607 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
608
609 <mml:mrow>
610 <mml:mfenced open="(" close=")">
611 <mml:mrow>
612 <mml:msup><mml:mn>2</mml:mn>
613 <mml:mn>N</mml:mn>
614 </mml:msup>
615 <mml:mo>-</mml:mo>
616 <mml:mn>1</mml:mn>
617 </mml:mrow>
618 </mml:mfenced>
619 <mml:mo>⁢</mml:mo>
620 <mml:mi mathvariant="italic">c</mml:mi>
621 </mml:mrow>
622 </mml:math>
623 </td></tr><tr><td align="left">
624 <code class="constant">GL_UNSIGNED_INT_8_8_8_8</code>
625 </td><td align="center">
626 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
627
628 <mml:mrow>
629 <mml:msup><mml:mn>2</mml:mn>
630 <mml:mn>N</mml:mn>
631 </mml:msup>
632 <mml:mo>-</mml:mo>
633 <mml:mn>1</mml:mn>
634 </mml:mrow>
635 </mml:math>
636 </td><td align="center">
637 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
638
639 <mml:mrow>
640 <mml:mfenced open="(" close=")">
641 <mml:mrow>
642 <mml:msup><mml:mn>2</mml:mn>
643 <mml:mn>N</mml:mn>
644 </mml:msup>
645 <mml:mo>-</mml:mo>
646 <mml:mn>1</mml:mn>
647 </mml:mrow>
648 </mml:mfenced>
649 <mml:mo>⁢</mml:mo>
650 <mml:mi mathvariant="italic">c</mml:mi>
651 </mml:mrow>
652 </mml:math>
653 </td></tr><tr><td align="left">
654 <code class="constant">GL_UNSIGNED_INT_8_8_8_8_REV</code>
655 </td><td align="center">
656 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
657
658 <mml:mrow>
659 <mml:msup><mml:mn>2</mml:mn>
660 <mml:mn>N</mml:mn>
661 </mml:msup>
662 <mml:mo>-</mml:mo>
663 <mml:mn>1</mml:mn>
664 </mml:mrow>
665 </mml:math>
666 </td><td align="center">
667 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
668
669 <mml:mrow>
670 <mml:mfenced open="(" close=")">
671 <mml:mrow>
672 <mml:msup><mml:mn>2</mml:mn>
673 <mml:mn>N</mml:mn>
674 </mml:msup>
675 <mml:mo>-</mml:mo>
676 <mml:mn>1</mml:mn>
677 </mml:mrow>
678 </mml:mfenced>
679 <mml:mo>⁢</mml:mo>
680 <mml:mi mathvariant="italic">c</mml:mi>
681 </mml:mrow>
682 </mml:math>
683 </td></tr><tr><td align="left">
684 <code class="constant">GL_UNSIGNED_INT_10_10_10_2</code>
685 </td><td align="center">
686 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
687
688 <mml:mrow>
689 <mml:msup><mml:mn>2</mml:mn>
690 <mml:mn>N</mml:mn>
691 </mml:msup>
692 <mml:mo>-</mml:mo>
693 <mml:mn>1</mml:mn>
694 </mml:mrow>
695 </mml:math>
696 </td><td align="center">
697 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
698
699 <mml:mrow>
700 <mml:mfenced open="(" close=")">
701 <mml:mrow>
702 <mml:msup><mml:mn>2</mml:mn>
703 <mml:mn>N</mml:mn>
704 </mml:msup>
705 <mml:mo>-</mml:mo>
706 <mml:mn>1</mml:mn>
707 </mml:mrow>
708 </mml:mfenced>
709 <mml:mo>⁢</mml:mo>
710 <mml:mi mathvariant="italic">c</mml:mi>
711 </mml:mrow>
712 </mml:math>
713 </td></tr><tr><td align="left">
714 <code class="constant">GL_UNSIGNED_INT_2_10_10_10_REV</code>
715 </td><td align="center">
716 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
717
718 <mml:mrow>
719 <mml:msup><mml:mn>2</mml:mn>
720 <mml:mn>N</mml:mn>
721 </mml:msup>
722 <mml:mo>-</mml:mo>
723 <mml:mn>1</mml:mn>
724 </mml:mrow>
725 </mml:math>
726 </td><td align="center">
727 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
728
729 <mml:mrow>
730 <mml:mfenced open="(" close=")">
731 <mml:mrow>
732 <mml:msup><mml:mn>2</mml:mn>
733 <mml:mn>N</mml:mn>
734 </mml:msup>
735 <mml:mo>-</mml:mo>
736 <mml:mn>1</mml:mn>
737 </mml:mrow>
738 </mml:mfenced>
739 <mml:mo>⁢</mml:mo>
740 <mml:mi mathvariant="italic">c</mml:mi>
741 </mml:mrow>
742 </mml:math>
743 </td></tr><tr><td align="left">
744 <code class="constant">GL_UNSIGNED_INT_24_8</code>
745 </td><td align="center">
746 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
747
748 <mml:mrow>
749 <mml:msup><mml:mn>2</mml:mn>
750 <mml:mn>N</mml:mn>
751 </mml:msup>
752 <mml:mo>-</mml:mo>
753 <mml:mn>1</mml:mn>
754 </mml:mrow>
755 </mml:math>
756 </td><td align="center">
757 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
758
759 <mml:mrow>
760 <mml:mfenced open="(" close=")">
761 <mml:mrow>
762 <mml:msup><mml:mn>2</mml:mn>
763 <mml:mn>N</mml:mn>
764 </mml:msup>
765 <mml:mo>-</mml:mo>
766 <mml:mn>1</mml:mn>
767 </mml:mrow>
768 </mml:mfenced>
769 <mml:mo>⁢</mml:mo>
770 <mml:mi mathvariant="italic">c</mml:mi>
771 </mml:mrow>
772 </mml:math>
773 </td></tr><tr><td align="left">
774 <code class="constant">GL_UNSIGNED_INT_10F_11F_11F_REV</code>
775 </td><td align="center">
776 --
777 </td><td align="left">
778 Special
779 </td></tr><tr><td align="left">
780 <code class="constant">GL_UNSIGNED_INT_5_9_9_9_REV</code>
781 </td><td align="center">
782 --
783 </td><td align="left">
784 Special
785 </td></tr><tr><td align="left">
786 <code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>
787 </td><td align="center">
788 none
789 </td><td align="center">
790 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">c</mml:mi></mml:math> (Depth Only)
791 </td></tr></tbody></table></div><p>
792 Return values are placed in memory as follows.
793 If <em class="parameter"><code>format</code></em> is
794 <code class="constant">GL_STENCIL_INDEX</code>,
795 <code class="constant">GL_DEPTH_COMPONENT</code>,
796 <code class="constant">GL_RED</code>,
797 <code class="constant">GL_GREEN</code>, or
798 <code class="constant">GL_BLUE</code>,
799 a single value is returned and the data for the
800 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
801 pixel in the
802 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
803 row
804 is placed in location
805 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
806
807 <mml:mrow>
808 <mml:mfenced open="(" close=")">
809 <mml:mi mathvariant="italic">j</mml:mi>
810 </mml:mfenced>
811 <mml:mo>⁢</mml:mo>
812 <mml:mi mathvariant="italic">width</mml:mi>
813 <mml:mo>+</mml:mo>
814 <mml:mi mathvariant="italic">i</mml:mi>
815 </mml:mrow>
816 </mml:math>.
817 <code class="constant">GL_RGB</code> and <code class="constant">GL_BGR</code> return three values,
818 <code class="constant">GL_RGBA</code> and <code class="constant">GL_BGRA</code> return four values for each pixel,
819 with all values corresponding to a single pixel occupying contiguous space
820 in <em class="parameter"><code>data</code></em>.
821 Storage parameters set by <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>,
822 such as <code class="constant">GL_PACK_LSB_FIRST</code> and <code class="constant">GL_PACK_SWAP_BYTES</code>,
823 affect the way that data is written into memory.
824 See <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a> for a description.
825 </p></div><div class="refsect1" title="Notes"><a id="notes"></a><h2>Notes</h2><p>
826 Values for pixels that lie outside the window
827 connected to the current GL context are undefined.
828 </p><p>
829 If an error is generated,
830 no change is made to the contents of <em class="parameter"><code>data</code></em>.
831 </p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p>
832 <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>format</code></em> or <em class="parameter"><code>type</code></em> is not an
833 accepted value.
834 </p><p>
835 <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.
836 </p><p>
837 <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>format</code></em> is <code class="constant">GL_STENCIL_INDEX</code>
838 and there is no stencil buffer.
839 </p><p>
840 <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>format</code></em> is <code class="constant">GL_DEPTH_COMPONENT</code>
841 and there is no depth buffer.
842 </p><p>
843 <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>format</code></em> is <code class="constant">GL_DEPTH_STENCIL</code>
844 and there is no depth buffer or if there is no stencil buffer.
845 </p><p>
846 <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>format</code></em> is <code class="constant">GL_DEPTH_STENCIL</code>
847 and <em class="parameter"><code>type</code></em> is not <code class="constant">GL_UNSIGNED_INT_24_8</code> or <code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>.
848 </p><p>
849 <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>type</code></em> is one of
850 <code class="constant">GL_UNSIGNED_BYTE_3_3_2</code>,
851 <code class="constant">GL_UNSIGNED_BYTE_2_3_3_REV</code>,
852 <code class="constant">GL_UNSIGNED_SHORT_5_6_5</code>, or
853 <code class="constant">GL_UNSIGNED_SHORT_5_6_5_REV</code>
854 and <em class="parameter"><code>format</code></em> is not <code class="constant">GL_RGB</code>.
855 </p><p>
856 <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>type</code></em> is one of
857 <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4</code>,
858 <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4_REV</code>,
859 <code class="constant">GL_UNSIGNED_SHORT_5_5_5_1</code>,
860 <code class="constant">GL_UNSIGNED_SHORT_1_5_5_5_REV</code>,
861 <code class="constant">GL_UNSIGNED_INT_8_8_8_8</code>,
862 <code class="constant">GL_UNSIGNED_INT_8_8_8_8_REV</code>,
863 <code class="constant">GL_UNSIGNED_INT_10_10_10_2</code>, or
864 <code class="constant">GL_UNSIGNED_INT_2_10_10_10_REV</code>
865 and <em class="parameter"><code>format</code></em> is neither <code class="constant">GL_RGBA</code> nor <code class="constant">GL_BGRA</code>.
866 </p><p>
867 <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
868 <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and the buffer object's data store is currently mapped.
869 </p><p>
870 <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
871 <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and the data would be packed to the buffer
872 object such that the memory writes required would exceed the data store size.
873 </p><p>
874 <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
875 <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and <em class="parameter"><code>data</code></em> is not evenly divisible
876 into the number of bytes needed to store in memory a datum indicated by <em class="parameter"><code>type</code></em>.
877 </p><p>
878 <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="constant">GL_READ_FRAMEBUFFER_BINDING</code>
879 is non-zero, the read framebuffer is complete, and the value of <code class="constant">GL_SAMPLE_BUFFERS</code>
880 for the read framebuffer is greater than zero.
881 </p></div><div class="refsect1" title="Associated Gets"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
882 <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_INDEX_MODE</code>
883 </p><p>
884 <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_PIXEL_PACK_BUFFER_BINDING</code>
885 </p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
886 <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>,
887 <a class="citerefentry" href="glReadBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a>
888 </p></div><div class="refsect1" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p>
889 Copyright <span class="trademark"></span>© 1991-2006
890 Silicon Graphics, Inc. This document is licensed under the SGI
891 Free Software B License. For details, see
892 <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
893 </p></div></div></body></html>
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