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    <title>sampler_t</title>
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      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="sampler_t"></a>
        <h1> sampler_t</h1>
        <p>
            A type used to control how elements of a 2D or 3D image object are read by <code xmlns="http://www.w3.org/1999/xhtml" class="function">read_image{f|i|ui}</code>.
        </p>
      </div>
      <div class="refsect2">
        <a id="synopsis"></a>
        <h3>
        </h3>
        <div class="informaltable">
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                <td align="left">
const sampler_t &lt;sampler name&gt; = &lt;value&gt;
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="description"></a>
        <h2>Description</h2>
        <p>
The image read functions take a sampler argument. The sampler can be passed as an argument
to the kernel using <a class="citerefentry" href="clSetKernelArg.html"><span class="citerefentry"><span class="refentrytitle">clSetKernelArg</span></span></a>, or it can be a constant variable of type <span class="type">sampler_t</span> declared in the program source.
        </p>
        <p>
Sampler variables in a program are declared to be of type <span class="type">sampler_t</span>.
The <span class="type">sampler_t</span> type is a 32-bit unsigned int constant and is interpreted as a bit-field that specifies the following properties:
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem">
              <p>
            Addressing Mode
       </p>
            </li>
            <li class="listitem">
              <p>
            Filter Mode
       </p>
            </li>
            <li class="listitem">
              <p>
           Normalized Coordinates
       </p>
            </li>
          </ul>
        </div>
        <p>
These properties control how elements of a 2D or 3D image object are read by
<a class="citerefentry" href="imageFunctions.html"><span class="citerefentry"><span class="refentrytitle">read_image{f|i|ui}</span></span></a>.
        </p>
        <p>
Samplers can also be declared as global constants in the program source using the syntax shown at the top of this page.
        </p>
        <p>
The sampler fields are described in the table below:
        </p>
        <p>
        </p>
        <div class="informaltable">
          <table border="1">
            <colgroup>
              <col align="left" class="col1" />
              <col align="left" class="col2" />
            </colgroup>
            <thead>
              <tr>
                <th align="left">Sampler State</th>
                <th align="left">Description</th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td align="left">
<p>
<code class="constant">&lt;normalized coords&gt;</code>
</p>
                        </td>
                <td align="left">
<p>
Specifies whether the <code class="varname">x</code>, <code class="varname">y</code> and <code class="varname">z</code> coordinates are passed in as normalized or unnormalized values. This must be one of the following predefined enums:
</p>

<p>
</p><div class="literallayout"><p>CLK_NORMALIZED_COORDS_TRUE or<br />
CLK_NORMALIZED_COORDS_FALSE.</p></div><p>
</p>

<p>
In OpenCL 1.0, the samplers specified with an image in multiple <code class="function">read_image{f|i|ui}</code> calls declared in a kernel must use
the same value for <code class="constant">&lt;normalized coords&gt;</code>.
</p>
                        </td>
              </tr>
              <tr>
                <td align="left">
<p>
<code class="constant">&lt;address mode&gt;</code>
</p>
                        </td>
                <td align="left">
<p>
Specifies the image addressing-mode i.e. how out-of-range
image coordinates are handled. This must be a literal value
and can be one of the following predefined enums:
</p>

<p>
CLK_ADDRESS_REPEAT - out-of-range image coordinates
are wrapped to the valid range. This <code class="constant">address mode</code> can
only be used with normalized coordinates. If normalized
coordinates are not used, this addressing mode may generate
image coordinates that are undefined.
</p>

<p>
CLK_ADDRESS_CLAMP_TO_EDGE - out-of-range image
coordinates are clamped to the extent.
</p>

<p>
CLK_ADDRESS_CLAMP<sup>32</sup> - out-of-range image coordinates
will return a border color. The border color is (<code class="constant">0.0f</code>,
<code class="constant">0.0f</code>, <code class="constant">0.0f</code>, <code class="constant">0.0f</code>) if image channel order is CL_A,
CL_INTENSITY, CL_RA, CL_ARGB, CL_BGRA or CL_RGBA
and is (<code class="constant">0.0f</code>, <code class="constant">0.0f</code>,
<code class="constant">0.0f</code>, <code class="constant">1.0f</code>) if image channel
order is CL_R, CL_RG, CL_RGB or CL_LUMINANCE.
</p>

<p>
CLK_ADDRESS_NONE - for this address mode the
programmer guarantees that the image coordinates used to
sample elements of the image refer to a location inside the
image; otherwise the results are undefined.
</p>
                        </td>
              </tr>
              <tr>
                <td align="left">
<p>
<code class="constant">&lt;filter mode&gt;</code>
</p>
                        </td>
                <td align="left">
<p>
Specifies the filtering mode to use. This must be a literal value
and can be one of the following predefined enums:
CLK_FILTER_NEAREST or CLK_FILTER_LINEAR.
</p>


<p>
Refer to section on Image Addressing and Filtering in the <a href="http://www.khronos.org/registry/cl/specs/opencl-1.x-latest.pdf#page=212" target="OpenCL Spec">OpenCL specification</a> for a description of these filtering modes.
</p>
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
	</p>
        <p>
Samplers cannot be declared as arrays, pointers, or be used as the type for local variables inside a function or as the return value of a function defined in a program. Samplers cannot be passed as arguments to functions called by a <a class="citerefentry" href="functionQualifiers.html"><span class="citerefentry"><span class="refentrytitle">__kernel</span></span></a> function.
A sampler argument to a <a class="citerefentry" href="functionQualifiers.html"><span class="citerefentry"><span class="refentrytitle">__kernel</span></span></a>
function cannot be modified.
</p>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
The maximum number of samplers that can be declared in a kernel can be queried using the
<code class="constant">CL_DEVICE_MAX_SAMPLERS</code> token in the table of OpenCL Device Queries for <a class="citerefentry" href="clGetDeviceInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetDeviceInfo</span></span></a>.
        </p>
      </div>
      <div class="refsect2">
        <a id="example1"></a>
        <h3>
            Example
        </h3>
        <div class="informaltable">
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                <td align="left">
const sampler_t samplerA = CLK_NORMALIZED_COORDS_TRUE |
                           CLK_ADDRESS_REPEAT         |
                           CLK_FILTER_NEAREST;
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
samplerA specifies a sampler that uses normalized coordinates, the repeat addressing mode and
a nearest filter.
</p>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p>
            <img src="pdficon_small1.gif" />
                                                 
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.x-latest.pdf#page=130" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
            <a class="citerefentry" href="otherDataTypes.html"><span class="citerefentry"><span class="refentrytitle">Other Data Types</span></span></a>,
<a class="citerefentry" href="imageFunctions.html"><span class="citerefentry"><span class="refentrytitle">Image Read and Write Functions</span></span></a>,

        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2009 The Khronos Group Inc. 
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
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