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-<?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>
+<?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
- OpenGL 3.3 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><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"><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">glReadPixels</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">format</var>, </td></tr><tr><td> </td><td>GLenum </td><td><var class="pdparam">type</var>, </td></tr><tr><td> </td><td>GLvoid * </td><td><var class="pdparam">data</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>
Specify the window coordinates of the first pixel
that is read from the frame buffer.
This location is the lower left corner of a rectangular block of pixels.
<code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>.
</p></dd><dt><span class="term"><em class="parameter"><code>data</code></em></span></dt><dd><p>
Returns the pixel data.
- </p></dd></dl></div></div><div class="refsect1"
title="Description"><a id="description"></a><h2>Description</h2><p>
+ </p></dd></dl></div></div><div class="refsect1"
lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
<code class="function">glReadPixels</code> returns pixel data from the frame buffer,
starting with the pixel whose lower left corner
is at location (<em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em>),
into client memory starting at location <em class="parameter"><code>data</code></em>.
Several parameters control the processing of the pixel data before
it is placed into client memory.
- These parameters are set with <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>.
+ These parameters are set with <a href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>.
This reference page describes the effects on <code class="function">glReadPixels</code> of most,
but not all of the parameters specified by these three commands.
</p><p>
If a non-zero named buffer object is bound to the <code class="constant">GL_PIXEL_PACK_BUFFER</code> target
- (see <a class="citerefentry" href="glBindBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glBindBuffer</span></span></a>) while a block of pixels is
+ (see <a href="glBindBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glBindBuffer</span></span></a>) while a block of pixels is
requested, <em class="parameter"><code>data</code></em> is treated as a byte offset into the buffer object's data store
rather than a pointer to client memory.
</p><p>
accepted values are:
</p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_STENCIL_INDEX</code></span></dt><dd><p>
Stencil values are read from the stencil buffer.
- Each index is converted to fixed point,
- shifted left or right depending on the value and sign of <code class="constant">GL_INDEX_SHIFT</code>,
- and added to <code class="constant">GL_INDEX_OFFSET</code>.
- If <code class="constant">GL_MAP_STENCIL</code> is <code class="constant">GL_TRUE</code>,
- indices are replaced by their mappings in the table <code class="constant">GL_PIXEL_MAP_S_TO_S</code>.
+ Each index is converted to fixed point.
</p></dd><dt><span class="term"><code class="constant">GL_DEPTH_COMPONENT</code></span></dt><dd><p>
Depth values are read from the depth buffer.
Each component is converted to floating point such that the minimum depth
value maps to 0 and the maximum value maps to 1.
- Each component is then multiplied by <code class="constant">GL_DEPTH_SCALE</code>,
- added to <code class="constant">GL_DEPTH_BIAS</code>,
- and finally clamped to the range
+ Each component is clamped to the range
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<code class="constant">GL_RGBA</code> and <code class="constant">GL_BGRA</code> return four values for each pixel,
with all values corresponding to a single pixel occupying contiguous space
in <em class="parameter"><code>data</code></em>.
- Storage parameters set by <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>,
+ Storage parameters set by <a href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>,
such as <code class="constant">GL_PACK_LSB_FIRST</code> and <code class="constant">GL_PACK_SWAP_BYTES</code>,
affect the way that data is written into memory.
- See <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a> for a description.
- </p></div><div class="refsect1"
title="Notes"><a id="notes"></a><h2>Notes</h2><p>
+ See <a href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a> for a description.
+ </p></div><div class="refsect1"
lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
Values for pixels that lie outside the window
connected to the current GL context are undefined.
</p><p>
If an error is generated,
no change is made to the contents of <em class="parameter"><code>data</code></em>.
- </p></div><div class="refsect1"
title="Errors"><a id="errors"></a><h2>Errors</h2><p>
+ </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>format</code></em> or <em class="parameter"><code>type</code></em> is not an
accepted value.
</p><p>
<code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="constant">GL_READ_FRAMEBUFFER_BINDING</code>
is non-zero, the read framebuffer is complete, and the value of <code class="constant">GL_SAMPLE_BUFFERS</code>
for the read framebuffer is greater than zero.
- </p></div><div class="refsect1" title="Associated Gets"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
- <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>
- </p><p>
- <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>
- </p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
- <a class="citerefentry" href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>,
- <a class="citerefentry" href="glReadBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a>
- </p></div><div class="refsect1" title="Copyright"><a id="Copyright"></a><h2>Copyright</h2><p>
+ </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
+ <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_PIXEL_PACK_BUFFER_BINDING</code>
+ </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
+ <a href="glPixelStore.xml"><span class="citerefentry"><span class="refentrytitle">glPixelStore</span></span></a>,
+ <a href="glReadBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glReadBuffer</span></span></a>
+ </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
Copyright <span class="trademark"></span>© 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
- <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
+ <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
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