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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 - OpenGL 4 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.
                </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>
                    Specify the dimensions of the pixel rectangle.
                    <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> of one correspond to a single pixel.
                </p></dd><dt><span class="term"><em class="parameter"><code>format</code></em></span></dt><dd><p>
                    Specifies the format of the pixel data.
                    The following symbolic values are accepted:
                    <code class="constant">GL_STENCIL_INDEX</code>,
                    <code class="constant">GL_DEPTH_COMPONENT</code>,
                    <code class="constant">GL_DEPTH_STENCIL</code>,
                    <code class="constant">GL_RED</code>,
                    <code class="constant">GL_GREEN</code>,
                    <code class="constant">GL_BLUE</code>,
                    <code class="constant">GL_RGB</code>,
                    <code class="constant">GL_BGR</code>,
                    <code class="constant">GL_RGBA</code>, and
                    <code class="constant">GL_BGRA</code>.
                </p></dd><dt><span class="term"><em class="parameter"><code>type</code></em></span></dt><dd><p>
                    Specifies the data type of the pixel data.
                    Must be one of
                    <code class="constant">GL_UNSIGNED_BYTE</code>,
                    <code class="constant">GL_BYTE</code>,
                    <code class="constant">GL_UNSIGNED_SHORT</code>,
                    <code class="constant">GL_SHORT</code>,
                    <code class="constant">GL_UNSIGNED_INT</code>,
                    <code class="constant">GL_INT</code>,
                    <code class="constant">GL_HALF_FLOAT</code>,
                    <code class="constant">GL_FLOAT</code>,
                    <code class="constant">GL_UNSIGNED_BYTE_3_3_2</code>,
                    <code class="constant">GL_UNSIGNED_BYTE_2_3_3_REV</code>,
                    <code class="constant">GL_UNSIGNED_SHORT_5_6_5</code>,
                    <code class="constant">GL_UNSIGNED_SHORT_5_6_5_REV</code>,
                    <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4</code>,
                    <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4_REV</code>,
                    <code class="constant">GL_UNSIGNED_SHORT_5_5_5_1</code>,
                    <code class="constant">GL_UNSIGNED_SHORT_1_5_5_5_REV</code>,
                    <code class="constant">GL_UNSIGNED_INT_8_8_8_8</code>,
                    <code class="constant">GL_UNSIGNED_INT_8_8_8_8_REV</code>,
                    <code class="constant">GL_UNSIGNED_INT_10_10_10_2</code>,
                    <code class="constant">GL_UNSIGNED_INT_2_10_10_10_REV</code>,
                    <code class="constant">GL_UNSIGNED_INT_24_8</code>,
                    <code class="constant">GL_UNSIGNED_INT_10F_11F_11F_REV</code>,
                    <code class="constant">GL_UNSIGNED_INT_5_9_9_9_REV</code>, or
                    <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" 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 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 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>
            <code class="function">glReadPixels</code> returns values from each pixel with lower left corner at
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            row.
            Pixels are returned in row order from the lowest to the highest row,
            left to right in each row.
        </p><p>
            <em class="parameter"><code>format</code></em> specifies the format for the returned pixel values;
            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>.
                    </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 
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                    </p></dd><dt><span class="term"><code class="constant">GL_DEPTH_STENCIL</code></span></dt><dd><p>
                        Values are taken from both the depth and stencil buffers. The <em class="parameter"><code>type</code></em> parameter
                        must be <code class="constant">GL_UNSIGNED_INT_24_8</code> or <code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>.
                    </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>
            Finally, the indices or components
            are converted to the proper format,
            as specified by <em class="parameter"><code>type</code></em>.
            If <em class="parameter"><code>format</code></em> is <code class="constant">GL_STENCIL_INDEX</code>
            and <em class="parameter"><code>type</code></em> is not <code class="constant">GL_FLOAT</code>,
            each index is masked with the mask value given in the following table.
            If <em class="parameter"><code>type</code></em> is <code class="constant">GL_FLOAT</code>, then each integer index is converted to
            single-precision floating-point format.
        </p><p>
            If <em class="parameter"><code>format</code></em> is
            <code class="constant">GL_RED</code>,
            <code class="constant">GL_GREEN</code>,
            <code class="constant">GL_BLUE</code>,
            <code class="constant">GL_RGB</code>,
            <code class="constant">GL_BGR</code>,
            <code class="constant">GL_RGBA</code>, or
            <code class="constant">GL_BGRA</code> and <em class="parameter"><code>type</code></em> is not <code class="constant">GL_FLOAT</code>,
            each component is multiplied by the multiplier shown in the following table.
            If type is <code class="constant">GL_FLOAT</code>, then each component is passed as is
            (or converted to the client's single-precision floating-point format if
            it is different from the one used by the GL).
        </p><p>
        </p><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /><col align="center" /></colgroup><thead><tr><th align="left">
                        <em class="parameter"><code>type</code></em>
                        </th><th align="center"><span class="bold"><strong>
                        Index Mask
                        </strong></span></th><th align="center"><span class="bold"><strong>
                        Component Conversion
                        </strong></span></th></tr></thead><tbody><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_BYTE</code>
                        </td><td align="center">
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                        <code class="constant">GL_BYTE</code>
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                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT</code>
                        </td><td align="center">
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                        <code class="constant">GL_SHORT</code>
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                        <code class="constant">GL_UNSIGNED_INT</code>
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                        </td></tr><tr><td align="left">
                        <code class="constant">GL_HALF_FLOAT</code>
                        </td><td align="center">
                        none
                        </td><td align="center">
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                        <code class="constant">GL_FLOAT</code>
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                        <code class="constant">GL_UNSIGNED_BYTE_3_3_2</code>
                        </td><td align="center">
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                        <code class="constant">GL_UNSIGNED_BYTE_2_3_3_REV</code>
                        </td><td align="center">
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                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT_5_6_5</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT_5_6_5_REV</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4_REV</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT_5_5_5_1</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_SHORT_1_5_5_5_REV</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_8_8_8_8</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_8_8_8_8_REV</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_10_10_10_2</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_2_10_10_10_REV</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_24_8</code>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:msup><mml:mn>2</mml:mn>
                                <mml:mn>N</mml:mn>
                                </mml:msup>
                                <mml:mo>-</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:math>
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                            
                            <mml:mrow>
                                <mml:mfenced open="(" close=")">
                                    <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mn>N</mml:mn>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mo>⁢</mml:mo>
                                <mml:mi mathvariant="italic">c</mml:mi>
                            </mml:mrow>
                        </mml:math>
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_10F_11F_11F_REV</code>
                        </td><td align="center">
                        --
                        </td><td align="left">
                        Special
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_UNSIGNED_INT_5_9_9_9_REV</code>
                        </td><td align="center">
                        --
                        </td><td align="left">
                        Special
                        </td></tr><tr><td align="left">
                        <code class="constant">GL_FLOAT_32_UNSIGNED_INT_24_8_REV</code>
                        </td><td align="center">
                        none
                        </td><td align="center">
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">c</mml:mi></mml:math> (Depth Only)
                        </td></tr></tbody></table></div><p>
            Return values are placed in memory as follows.
            If <em class="parameter"><code>format</code></em> is
            <code class="constant">GL_STENCIL_INDEX</code>,
            <code class="constant">GL_DEPTH_COMPONENT</code>,
            <code class="constant">GL_RED</code>,
            <code class="constant">GL_GREEN</code>, or
            <code class="constant">GL_BLUE</code>,
            a single value is returned and the data for the 
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>th
            pixel in the 
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>th
            row
            is placed in location 
            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                
                <mml:mrow>
                    <mml:mfenced open="(" close=")">
                        <mml:mi mathvariant="italic">j</mml:mi>
                    </mml:mfenced>
                    <mml:mo>⁢</mml:mo>
                    <mml:mi mathvariant="italic">width</mml:mi>
                    <mml:mo>+</mml:mo>
                    <mml:mi mathvariant="italic">i</mml:mi>
                </mml:mrow>
            </mml:math>.
            <code class="constant">GL_RGB</code> and <code class="constant">GL_BGR</code> return three values,
            <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 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 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" 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_VALUE</code> is generated if either <em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em> is negative.
        </p><p>
            <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>
            and there is no stencil buffer.
        </p><p>
            <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>
            and there is no depth buffer.
        </p><p>
            <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>
            and there is no depth buffer or if there is no stencil buffer.
        </p><p>
            <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>
            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>.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>type</code></em> is one of
            <code class="constant">GL_UNSIGNED_BYTE_3_3_2</code>,
            <code class="constant">GL_UNSIGNED_BYTE_2_3_3_REV</code>,
            <code class="constant">GL_UNSIGNED_SHORT_5_6_5</code>, or
            <code class="constant">GL_UNSIGNED_SHORT_5_6_5_REV</code>
            and <em class="parameter"><code>format</code></em> is not <code class="constant">GL_RGB</code>.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>type</code></em> is one of
            <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4</code>,
            <code class="constant">GL_UNSIGNED_SHORT_4_4_4_4_REV</code>,
            <code class="constant">GL_UNSIGNED_SHORT_5_5_5_1</code>,
            <code class="constant">GL_UNSIGNED_SHORT_1_5_5_5_REV</code>,
            <code class="constant">GL_UNSIGNED_INT_8_8_8_8</code>,
            <code class="constant">GL_UNSIGNED_INT_8_8_8_8_REV</code>,
            <code class="constant">GL_UNSIGNED_INT_10_10_10_2</code>, or
            <code class="constant">GL_UNSIGNED_INT_2_10_10_10_REV</code>
            and <em class="parameter"><code>format</code></em> is neither <code class="constant">GL_RGBA</code> nor <code class="constant">GL_BGRA</code>.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
            <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and the buffer object's data store is currently mapped.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
            <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and the data would be packed to the buffer 
            object such that the memory writes required would exceed the data store size.
        </p><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to the
            <code class="constant">GL_PIXEL_PACK_BUFFER</code> target and <em class="parameter"><code>data</code></em> is not evenly divisible 
            into the number of bytes needed to store in memory a datum indicated by <em class="parameter"><code>type</code></em>.
        </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" 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_INDEX_MODE</code>
        </p><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 href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>
