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- <refentry id="vidioc-g-crop">
- <refmeta>
- <refentrytitle>ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</refentrytitle>
- &manvol;
- </refmeta>
- <refnamediv>
- <refname>VIDIOC_G_CROP</refname>
- <refname>VIDIOC_S_CROP</refname>
- <refpurpose>Get or set the current cropping rectangle</refpurpose>
- </refnamediv>
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>int <function>ioctl</function></funcdef>
- <paramdef>int <parameter>fd</parameter></paramdef>
- <paramdef>int <parameter>request</parameter></paramdef>
- <paramdef>struct v4l2_crop *<parameter>argp</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- <funcsynopsis>
- <funcprototype>
- <funcdef>int <function>ioctl</function></funcdef>
- <paramdef>int <parameter>fd</parameter></paramdef>
- <paramdef>int <parameter>request</parameter></paramdef>
- <paramdef>const struct v4l2_crop *<parameter>argp</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
- <refsect1>
- <title>Arguments</title>
- <variablelist>
- <varlistentry>
- <term><parameter>fd</parameter></term>
- <listitem>
- <para>&fd;</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>request</parameter></term>
- <listitem>
- <para>VIDIOC_G_CROP, VIDIOC_S_CROP</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>argp</parameter></term>
- <listitem>
- <para></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
- <refsect1>
- <title>Description</title>
- <para>To query the cropping rectangle size and position
- applications set the <structfield>type</structfield> field of a
- <structname>v4l2_crop</structname> structure to the respective buffer
- (stream) type and call the <constant>VIDIOC_G_CROP</constant> ioctl
- with a pointer to this structure. The driver fills the rest of the
- structure or returns the &EINVAL; if cropping is not supported.</para>
- <para>To change the cropping rectangle applications initialize the
- <structfield>type</structfield> and &v4l2-rect; substructure named
- <structfield>c</structfield> of a v4l2_crop structure and call the
- <constant>VIDIOC_S_CROP</constant> ioctl with a pointer to this
- structure.</para>
- <para>Do not use the multiplanar buffer types. Use <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>
- instead of <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>
- and use <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> instead of
- <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>.</para>
- <para>The driver first adjusts the requested dimensions against
- hardware limits, &ie; the bounds given by the capture/output window,
- and it rounds to the closest possible values of horizontal and
- vertical offset, width and height. In particular the driver must round
- the vertical offset of the cropping rectangle to frame lines modulo
- two, such that the field order cannot be confused.</para>
- <para>Second the driver adjusts the image size (the opposite
- rectangle of the scaling process, source or target depending on the
- data direction) to the closest size possible while maintaining the
- current horizontal and vertical scaling factor.</para>
- <para>Finally the driver programs the hardware with the actual
- cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a
- write-only ioctl, it does not return the actual parameters. To query
- them applications must call <constant>VIDIOC_G_CROP</constant> and
- &VIDIOC-G-FMT;. When the parameters are unsuitable the application may
- modify the cropping or image parameters and repeat the cycle until
- satisfactory parameters have been negotiated.</para>
- <para>When cropping is not supported then no parameters are
- changed and <constant>VIDIOC_S_CROP</constant> returns the
- &EINVAL;.</para>
- <table pgwide="1" frame="none" id="v4l2-crop">
- <title>struct <structname>v4l2_crop</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>type</structfield></entry>
- <entry>Type of the data stream, set by the application.
- Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
- <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and
- <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry>
- </row>
- <row>
- <entry>&v4l2-rect;</entry>
- <entry><structfield>c</structfield></entry>
- <entry>Cropping rectangle. The same co-ordinate system as
- for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
- <refsect1>
- &return-value;
- </refsect1>
- </refentry>
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