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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry>
<refentryinfo>
<keywordset>
<keyword>clEnqueueReadImage</keyword>
</keywordset>
</refentryinfo>
<refmeta>
<refentrytitle>
clEnqueueReadImage
</refentrytitle>
<refmiscinfo>
<copyright>
<year>2007-2011</year>
<holder>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.</holder>
</copyright>
</refmiscinfo>
<manvolnum>3</manvolnum>
</refmeta>
<!-- ================================ SYNOPSIS -->
<refnamediv id="clEnqueueReadImage">
<refname>
clEnqueueReadImage
</refname>
<refpurpose>
Enqueue commands to read from an image or image array object to host memory.
</refpurpose>
</refnamediv>
<refsynopsisdiv xmlns:xlink="http://www.w3.org/1999/xlink"><title></title>
<funcsynopsis>
<funcprototype>
<funcdef>
<link xlink:href="scalarDataTypes.html">cl_int</link>
<function>clEnqueueReadImage</function>
</funcdef>
<paramdef>
<link xlink:href="abstractDataTypes.html">cl_command_queue</link>
<parameter>command_queue</parameter>
</paramdef>
<paramdef>
<link xlink:href="abstractDataTypes.html">cl_mem</link>
<parameter>image</parameter>
</paramdef>
<paramdef>
<link xlink:href="enums.html#cl_bool">cl_bool</link>
<parameter>blocking_read</parameter>
</paramdef>
<paramdef>const
<link xlink:href="scalarDataTypes.html">size_t</link>
<parameter>*origin</parameter>
</paramdef>
<paramdef>const
<link xlink:href="scalarDataTypes.html">size_t</link>
<parameter>*region</parameter>
</paramdef>
<paramdef>
<link xlink:href="scalarDataTypes.html">size_t</link>
<parameter>row_pitch</parameter>
</paramdef>
<paramdef>
<link xlink:href="scalarDataTypes.html">size_t</link>
<parameter>slice_pitch</parameter>
</paramdef>
<paramdef>
<link xlink:href="scalarDataTypes.html">void</link>
<parameter>*ptr</parameter>
</paramdef>
<paramdef>
<link xlink:href="scalarDataTypes.html">cl_uint</link>
<parameter>num_events_in_wait_list</parameter>
</paramdef>
<paramdef>const
<link xlink:href="abstractDataTypes.html">cl_event</link>
<parameter>*event_wait_list</parameter>
</paramdef>
<paramdef>
<link xlink:href="abstractDataTypes.html">cl_event</link><parameter>*event</parameter>
</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- ================================ PARAMETERS -->
<refsect1 id="parameters">
<title>Parameters</title>
<variablelist>
<varlistentry>
<term> <varname> command_queue </varname> </term>
<listitem>
<para>
Refers to the command-queue in which the read command will be
queued. <varname>command_queue</varname> and <varname>image</varname>
must be created with the same OpenCL context.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> image </varname> </term>
<listitem>
<para>
Refers to a valid image or image array object.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> blocking_read </varname> </term>
<listitem>
<para>
Indicates if the read operations are <varname>blocking</varname> or
<varname>non-blocking</varname>.
</para>
<para>
If <varname>blocking_read</varname> is <constant>CL_TRUE</constant>
i.e. the read command is blocking, <function>clEnqueueReadImage</function>
does not return until the buffer data has been read and copied into memory
pointed to by <varname>ptr</varname>.
</para>
<para>
If <varname>blocking_read</varname> is <constant>CL_FALSE</constant>
i.e. map operation is non-blocking, <function>clEnqueueReadImage</function>
queues a non-blocking read command and returns. The contents of the
buffer that <varname>ptr</varname> points to cannot be used until the read
command has completed. The <varname>event</varname> argument returns an
event object which can be used to query the execution status of the read
command. When the read command has completed, the contents of the buffer
that <varname>ptr</varname> points to can be used by the application.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> origin </varname> </term>
<listitem>
<para>
Defines the (<emphasis>x, y, z</emphasis>) offset in pixels in the 1D, 2D, or
3D image, the (<emphasis>x, y</emphasis>) offset and the image index in the
image array or the (x) offset and the image index in the 1D image array. If
<varname>image</varname> is a 2D image object, <varname>origin</varname>[2]
must be 0. If <varname>image</varname> is a 1D image or 1D image buffer
object, <varname>origin</varname>[1] and <varname>origin</varname>[2]
must be 0. If <varname>image</varname> is a 1D image array object,
<varname>origin</varname>[2] must be 0. If <varname>image</varname>
is a 1D image array object, <varname>origin</varname>[1] describes the
image index in the 1D image array. If <varname>image</varname> is a 2D
image array object, <varname>origin</varname>[2] describes the image
index in the 2D image array.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> region </varname> </term>
<listitem>
<para>
Defines the (<emphasis>width, height, depth</emphasis>) in pixels of the
1D, 2D or 3D rectangle, the (<emphasis>width, height</emphasis>) in pixels
of the 2D rectangle and the number of images of a 2D image array or the
(<emphasis>width</emphasis>) in pixels of the 1D rectangle and the number
of images of a 1D image array. If <varname>image</varname> is a 2D image
object, <varname>region</varname>[2] must be 1. If <varname>image</varname>
is a 1D image or 1D image buffer object, <varname>region</varname>[1]
and <varname>region</varname>[2] must be 1. If image is a 1D image array
object, <varname>region</varname>[2] must be 1.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> row_pitch </varname> </term>
<listitem>
<para>
The length of each row in bytes. This value must be greater than or
equal to the element size in bytes * <varname>width</varname>. If
<varname>row_pitch</varname> is set to 0, the appropriate row pitch
is calculated based on the size of each element in bytes multiplied by
<varname>width</varname>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> slice_pitch </varname> </term>
<listitem>
<para>
Size in bytes of the 2D slice of the 3D region of a 3D image or
each image of a 1D or 2D image array being read. This must be 0 if
<varname>image</varname> is a 1D or 2D image. This value must be greater
than or equal to <varname>row_pitch</varname> * <varname>height</varname>.
If <varname>slice_pitch</varname> is set to 0, the appropriate slice
pitch is calculated based on the <varname>row_pitch</varname> *
<varname>height</varname>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname> ptr </varname> </term>
<listitem>
<para>
The pointer to a buffer in host memory where image data is to be read from.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term> <varname>
event_wait_list
,</varname>
<varname>
num_events_in_wait_list
</varname>
</term>
<listitem>
<para>
Specify events that need to complete before this particular
command can be executed. If <varname>event_wait_list</varname>
is NULL, then this particular command does not wait on any
event to complete. If <varname>event_wait_list</varname> is
NULL, <varname>num_events_in_wait_list</varname> must be 0. If
<varname>event_wait_list</varname> is not NULL, the list of events
pointed to by <varname>event_wait_list</varname> must be valid
and <varname>num_events_in_wait_list</varname> must be greater
than 0. The events specified in <varname>event_wait_list</varname>
act as synchronization points. The context associated with events in
<varname>event_wait_list</varname> and <varname>command_queue</varname> must
be the same. The memory associated with <varname>event_wait_list</varname>
can be reused or freed after the function returns.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>
event
</varname>
</term>
<listitem>
<para>
Returns an event object that identifies this particular read command
and can be used to query or queue a wait for this particular command
to complete. <varname>event</varname> can be NULL in which case
it will not be possible for the application to query the status of
this command or queue a wait for this command to complete. If the
<varname>event_wait_list</varname> and the <varname>event</varname>
arguments are not NULL, the <varname>event</varname> argument should not
refer to an element of the <varname>event_wait_list</varname> array.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<!-- ================================ NOTES -->
<refsect1 id="notes"><title>Notes</title>
<para>
Calling <function>clEnqueueReadImage</function> to read a region of the
<varname>image</varname> with the <varname>ptr</varname> argument value set to
<varname>host_ptr</varname> + (<varname>origin</varname>[2] * <varname>image
slice pitch</varname> + <varname>origin</varname>[1] * <varname>image
row pitch</varname> + <varname>origin</varname>[0] * <varname>bytes per
pixel</varname>), where <varname>host_ptr</varname> is a pointer to the memory
region specified when the <varname>image</varname> being read is created with
<constant>CL_MEM_USE_HOST_PTR</constant>, must meet the following requirements in
order to avoid undefined behavior:
</para>
<itemizedlist mark="disc">
<listitem>
All commands that use this image object have finished execution before the read
command begins execution.
</listitem>
<listitem>
The <varname>row_pitch</varname> and <varname>slice_pitch</varname> argument
values in <function>clEnqueueReadImage</function> must be set to the image row
pitch and slice pitch.
</listitem>
<listitem>
The image object is not mapped.
</listitem>
<listitem>
The image object is not used by any command-queue until the read command has
finished execution.
</listitem>
</itemizedlist>
</refsect1>
<!-- ================================ ERRORS -->
<refsect1 id="errors"><title>Errors</title>
<para>
<function>clEnqueueReadImage</function> returns <errorname>CL_SUCCESS</errorname> if
the function is executed successfully. Otherwise, it returns one of the following errors.
</para>
<itemizedlist mark="disc">
<listitem>
<errorname>CL_INVALID_COMMAND_QUEUE</errorname> if <varname>command_queue</varname>
is not a valid command-queue.
</listitem>
<listitem>
<errorname>CL_INVALID_CONTEXT</errorname> if the context associated with
<varname>command_queue</varname> and <varname>image</varname> are not the same
or if the context associated with <varname>command_queue</varname> and events in
<varname>event_wait_list</varname> are not the same.
</listitem>
<listitem>
<errorname>CL_INVALID_MEM_OBJECT</errorname> if <varname>image</varname> is not
a valid image object.
</listitem>
<listitem>
<errorname>CL_INVALID_VALUE</errorname> if the region being read specified by
<varname>origin</varname> and <varname>region</varname> is out of bounds or if
<varname>ptr</varname> is a NULL value.
</listitem>
<listitem>
<errorname>CL_INVALID_VALUE</errorname> if values in <varname>origin</varname>
and <varname>region</varname> do not follow rules described in the argument
description for <varname>origin</varname> and <varname>region</varname>.
</listitem>
<listitem>
<errorname>CL_INVALID_EVENT_WAIT_LIST</errorname>
if <varname>event_wait_list</varname> is NULL and
<varname>num_events_in_wait_list</varname> > 0,
or <varname>event_wait_list</varname> is not NULL and
<varname>num_events_in_wait_list</varname> is 0, or if event objects in
<varname>event_wait_list</varname> are not valid events.
</listitem>
<listitem>
<errorname>CL_INVALID_IMAGE_SIZE</errorname> if image dimensions (image width,
height, specified or compute row and/or slice pitch) for <varname>image</varname>
are not supported by device associated with <varname>queue</varname>.
</listitem>
<listitem>
<errorname>CL_INVALID_IMAGE_FORMAT</errorname> if image format (image channel
order and data type) for <varname>image</varname> are not supported by device
associated with <varname>queue</varname>.
</listitem>
<listitem>
<errorname>CL_MEM_OBJECT_ALLOCATION_FAILURE</errorname> if there is a failure to
allocate memory for data store associated with <varname>image</varname>.
</listitem>
<listitem>
<errorname>CL_INVALID_OPERATION</errorname> if the device associated
with <varname>command_queue</varname> does not support images
(i.e. <constant>CL_DEVICE_IMAGE_SUPPORT</constant> specified in
the table of allowed values for <varname>param_name</varname> for
<citerefentry><refentrytitle>clGetDeviceInfo</refentrytitle></citerefentry>
is <constant>CL_FALSE</constant>).
</listitem>
<listitem>
<errorname>CL_INVALID_OPERATION</errorname> if
<function>clEnqueueReadImage</function> is called on <varname>image</varname>
which has been created with <constant>CL_MEM_HOST_WRITE_ONLY</constant> or
<constant>CL_MEM_HOST_NO_ACCESS</constant>
</listitem>
<listitem>
<errorname>CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST</errorname> if the read
and write operations are blocking and the execution status of any of the events
in <varname>event_wait_list</varname> is a negative integer value.
</listitem>
<listitem>
<errorname>CL_OUT_OF_RESOURCES</errorname> if there is a failure to allocate
resources required by the OpenCL implementation on the device.
</listitem>
<listitem>
<errorname>CL_OUT_OF_HOST_MEMORY</errorname> if there is a failure to allocate
resources required by the OpenCL implementation on the host.
</listitem>
</itemizedlist>
</refsect1>
<!-- ================================ EXAMPLE -->
<!-- DO NOT DELETE IN CASE AN EXAMPLE IS ADDED IN THE FUTURE -->
<!--
<refsect2 id="example1">
<title>
Example
</title>
<informaltable frame="none">
<tgroup cols="1" align="left" colsep="0" rowsep="0">
<colspec colname="col1" colnum="1" />
<tbody>
<row>
<entry>
Example goes here - it will be set in "code" type with white space preserved.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect2>
-->
<!-- ================================ SPECIFICATION -->
<!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page
-->
<refsect1 id="specification"><title>Specification</title>
<para>
<imageobject>
<imagedata fileref="pdficon_small1.gif" format="gif" />
</imageobject>
<olink uri="clEnqueueReadImage">OpenCL Specification</olink>
</para>
</refsect1>
<!-- ================================ ALSO SEE -->
<refsect1 id="seealso"><title>Also see</title>
<para>
<citerefentry><refentrytitle>clEnqueueWriteImage</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>clEnqueueCopyImage</refentrytitle></citerefentry>
</para>
</refsect1>
<!-- ================================ COPYRIGHT -->
<!-- Content included from copyright.inc.xsl -->
<refsect3 id="Copyright"><title></title>
<imageobject>
<imagedata fileref="KhronosLogo.jpg" format="jpg" />
</imageobject>
<para />
</refsect3>
<!-- 20-Oct-2011 -->
</refentry>
|
