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| </style> |
| <title>read_image (2D, Half)</title> |
| <meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /> |
| <meta name="keywords" content="read_imageh (2D, Half)" /> |
| </head> |
| <body> |
| <div class="refentry"> |
| <a id="id-1"></a> |
| <div class="titlepage"></div> |
| <div xmlns="" class="refnamediv"> |
| <a xmlns="http://www.w3.org/1999/xhtml" id="read_image2d"></a> |
| <h1>read_imageh (2D, Half)</h1> |
| <p> |
| Do an element lookup in the 2D image object, returning half floating-point values. |
| </p> |
| </div> |
| <div class="refsynopsisdiv"> |
| <h2></h2> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="vectorDataTypes.html" target="pagedisplay">half4</a> |
| <strong class="fsfunc"> |
| read_imageh |
| </strong> |
| (</code> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="otherDataTypes.html" target="pagedisplay">image2d_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">image</var> |
| , </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="sampler_t.html" target="pagedisplay">sampler_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">sampler</var> |
| , </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="vectorDataTypes.html" target="pagedisplay">int2</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">coord</var> |
| <code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="vectorDataTypes.html" target="pagedisplay">half4</a> |
| <strong class="fsfunc"> |
| read_imageh |
| </strong> |
| (</code> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="otherDataTypes.html" target="pagedisplay">image2d_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">image</var> |
| , </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="sampler_t.html" target="pagedisplay">sampler_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">sampler</var> |
| , </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="vectorDataTypes.html" target="pagedisplay">float2</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">coord</var> |
| <code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="vectorDataTypes.html" target="pagedisplay">half4</a> |
| <strong class="fsfunc"> |
| read_imageh |
| </strong> |
| (</code> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="otherDataTypes.html" target="pagedisplay">image2d_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">image</var> |
| , </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="vectorDataTypes.html" target="pagedisplay">int2</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">coord</var> |
| <code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="vectorDataTypes.html" target="pagedisplay">half4</a> |
| <strong class="fsfunc"> |
| read_imageh |
| </strong> |
| (</code> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="otherDataTypes.html" target="pagedisplay">image2d_array_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">image</var> |
| , </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="vectorDataTypes.html" target="pagedisplay">int4</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">coord</var> |
| <code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="vectorDataTypes.html" target="pagedisplay">half4</a> |
| <strong class="fsfunc"> |
| read_imageh |
| </strong> |
| (</code> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="otherDataTypes.html" target="pagedisplay">image2d_array_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">image</var> |
| , </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="sampler_t.html" target="pagedisplay">sampler_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">sampler</var> |
| , </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="vectorDataTypes.html" target="pagedisplay">int4</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">coord</var> |
| <code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="vectorDataTypes.html" target="pagedisplay">half4</a> |
| <strong class="fsfunc"> |
| read_imageh |
| </strong> |
| (</code> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="otherDataTypes.html" target="pagedisplay">image2d_array_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">image</var> |
| , </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="sampler_t.html" target="pagedisplay">sampler_t</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">sampler</var> |
| , </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td> |
| <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="vectorDataTypes.html" target="pagedisplay">float4</a> |
| <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">coord</var> |
| <code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="description"></a> |
| <h2>Description</h2> |
| <p> |
| For the forms that take an <span class="type">image2d_t</span>, use the coordinate <span class="emphasis"><em>(x, |
| y)</em></span> to do an element lookup in the 2D image object specified by |
| <code class="varname">image</code>. |
| </p> |
| <p> |
| For the forms that take an <span class="type">image2d_array_t</span>, Use |
| <span class="emphasis"><em>coord.xy</em></span> to do an element lookup in the 2D image identified by |
| <span class="emphasis"><em>coord.z</em></span> in the 2D image array specified by <code class="varname">image</code>. |
| </p> |
| <p> |
| The samplerless read image functions behave exactly as the corresponding read |
| image functions that take integer coordinates and a sampler with filter mode |
| set to <code class="constant">CLK_FILTER_NEAREST</code>, normalized coordinates set |
| to <code class="constant">CLK_NORMALIZED_COORDS_FALSE</code> and addressing mode to |
| <code class="constant">CLK_ADDRESS_NONE</code>. |
| </p> |
| <p> |
| <code class="function">read_imageh</code> returns half floating-point values in the range |
| [0.0... 1.0] for image objects created with <code class="varname">image_channel_data_type</code> |
| set to one of the predefined packed formats or <code class="constant">CL_UNORM_INT8</code> |
| or <code class="constant">CL_UNORM_INT16</code>. |
| </p> |
| <p> |
| <code class="function">read_imageh</code> returns half floating-point values in the range |
| [-1.0... 1.0] for image objects created with <code class="varname">image_channel_data_type</code> |
| set to <code class="constant">CL_SNORM_INT8</code>, or <code class="constant">CL_SNORM_INT16</code>. |
| </p> |
| <p> |
| <code class="function">read_imageh</code> returns half floating-point values for |
| image objects created with <code class="varname">image_channel_data_type</code> set to |
| <code class="constant">CL_HALF_FLOAT</code>. |
| </p> |
| <p> |
| The <code class="function">read_imageh</code> calls that take integer coordinates must |
| use a sampler with filter mode set to <code class="constant">CLK_FILTER_NEAREST</code>, |
| normalized coordinates set to <code class="constant">CLK_NORMALIZED_COORDS_FALSE</code> |
| and addressing mode set to <code class="constant">CLK_ADDRESS_CLAMP_TO_EDGE</code>, |
| <code class="constant">CLK_ADDRESS_CLAMP</code> or <code class="constant">CLK_ADDRESS_NONE</code>; |
| otherwise the values returned are undefined. |
| </p> |
| <p> |
| Values returned by <code class="function">read_imageh</code> for image objects with |
| <code class="varname">image_channel_data_type</code> values not specified in the description |
| above are undefined. |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="notes"></a> |
| <h2>Notes</h2> |
| <p> |
| General information about the <code class="function">read_image</code>* functions follows. |
| </p> |
| <p> |
| The built-in functions defined in this section |
| can only be used with image memory objects. An image memory object can be accessed by |
| specific function calls that read from and/or write to specific locations in the image. |
| </p> |
| <p> |
| Image memory objects that are being read by a kernel should be declared with the <a class="citerefentry" href="accessQualifiers.html"><span class="citerefentry"><span class="refentrytitle">__read_only</span></span></a> |
| qualifier. <code class="function">write_image</code> calls to image memory objects declared with the |
| <a class="citerefentry" href="accessQualifiers.html"><span class="citerefentry"><span class="refentrytitle">__read_only</span></span></a> |
| qualifier will generate a compilation error. Image memory objects that |
| are being written to by a kernel should be declared with the <a class="citerefentry" href="accessQualifiers.html"><span class="citerefentry"><span class="refentrytitle">__write_only</span></span></a> qualifier. |
| <code class="function">read_image</code> calls to image memory objects declared with the <a class="citerefentry" href="accessQualifiers.html"><span class="citerefentry"><span class="refentrytitle">__write_only</span></span></a> |
| qualifier will generate a compilation error. <code class="function">read_image</code> and |
| <code class="function">write_image</code> calls to the same image memory object in a kernel are |
| not supported. |
| </p> |
| <p> |
| The <code class="function">read_image</code> calls returns a four component floating-point, integer or |
| unsigned integer color value. The color values returned by <code class="function">read_image</code> |
| are identified as <code class="code">x, y, z, w</code> where <code class="code">x</code> refers to the red component, |
| <code class="code">y</code> refers to the green component, <code class="code">z</code> refers to the blue component |
| and <code class="code">w</code> refers to the alpha component. |
| </p> |
| <p> |
| The following table describes the mapping |
| of the number of channels of an image element to the appropriate components in the |
| <span class="type">float4</span>, <span class="type">int4</span> or <span class="type">uint4</span> vector data type for |
| the color values returned by <code class="function">read_image{f|i|ui}</code> or supplied |
| to <code class="function">write_image{f|i|ui}</code>. The unmapped components will be set |
| to <code class="constant">0.0</code> for red, green and blue channels and will be set to |
| <code class="constant">1.0</code> for the alpha channel. |
| </p> |
| <p> |
| </p> |
| <div class="informaltable"> |
| <table border="1"> |
| <colgroup> |
| <col align="center" class="col1" /> |
| <col align="center" class="col2" /> |
| </colgroup> |
| <thead> |
| <tr> |
| <th align="center">Channel Order</th> |
| <th align="center"><span class="type">float4</span>, <span class="type">int4</span> or <span class="type">uint4</span> components of channel data</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td align="center"><code class="constant">CL_R</code>, <code class="constant">CL_Rx</code></td> |
| <td align="center"> |
| <code class="constant">(r, 0.0, 0.0, 1.0)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"> |
| <code class="constant">CL_A</code> |
| </td> |
| <td align="center"> |
| <code class="constant">(0.0, 0.0, 0.0, a)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"><code class="constant">CL_RG</code>, <code class="constant">CL_RGx</code></td> |
| <td align="center"> |
| <code class="constant">(r, g, 0.0, 1.0)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"> |
| <code class="constant">CL_RA</code> |
| </td> |
| <td align="center"> |
| <code class="constant">(r, 0.0, 0.0, a)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"><code class="constant">CL_RGB</code>, <code class="constant">CL_RGBx</code></td> |
| <td align="center"> |
| <code class="constant">(r, g, b, 1.0)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"> |
| <code class="constant">CL_RGBA, CL_BGRA, CL_ARGB</code> |
| </td> |
| <td align="center"> |
| <code class="constant">(r, g, b, a)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"> |
| <code class="constant">CL_INTENSITY</code> |
| </td> |
| <td align="center"> |
| <code class="constant">(I, I, I, I)</code> |
| </td> |
| </tr> |
| <tr> |
| <td align="center"> |
| <code class="constant">CL_LUMINANCE</code> |
| </td> |
| <td align="center"> |
| <code class="constant">(L, L, L, 1.0)</code> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <p> |
| </p> |
| <p> |
| A kernel that uses a sampler with the <code class="constant">CL_ADDRESS_CLAMP</code> addressing |
| mode with multiple images may result in additional samplers being used internally |
| by an implementation. If the same sampler is used with multiple images called via |
| <code class="function">read_image{f|i|ui}</code>, then it is possible that an implementation may |
| need to allocate an additional sampler to handle the different border color values that |
| may be needed depending on the image formats being used. These implementation allocated |
| samplers will count against the maximum sampler values supported by the device and given by |
| <code class="constant">CL_DEVICE_MAX_SAMPLERS</code>. Enqueuing a kernel that requires more samplers |
| than the implementation can support will result in a <code class="constant">CL_OUT_OF_RESOURCES</code> |
| error being returned. |
| </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-1.2-extensions.pdf#page=27" target="OpenCL Spec">OpenCL Specification</a> |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="seealso"></a> |
| <h2>Also see</h2> |
| <p> |
| <a class="citerefentry" href="imageFunctions.html"><span class="citerefentry"><span class="refentrytitle">Image 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 © 2007-2011 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 |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials. |
| </div> |
| </div> |
| </body> |
| </html> |
