Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
1 <refentry id="vidioc-g-crop"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_G_CROP</refname> 9 <refname>VIDIOC_S_CROP</refname> 10 <refpurpose>Get or set the current cropping rectangle</refpurpose> 11 </refnamediv> 12 13 <refsynopsisdiv> 14 <funcsynopsis> 15 <funcprototype> 16 <funcdef>int <function>ioctl</function></funcdef> 17 <paramdef>int <parameter>fd</parameter></paramdef> 18 <paramdef>int <parameter>request</parameter></paramdef> 19 <paramdef>struct v4l2_crop *<parameter>argp</parameter></paramdef> 20 </funcprototype> 21 </funcsynopsis> 22 <funcsynopsis> 23 <funcprototype> 24 <funcdef>int <function>ioctl</function></funcdef> 25 <paramdef>int <parameter>fd</parameter></paramdef> 26 <paramdef>int <parameter>request</parameter></paramdef> 27 <paramdef>const struct v4l2_crop *<parameter>argp</parameter></paramdef> 28 </funcprototype> 29 </funcsynopsis> 30 </refsynopsisdiv> 31 32 <refsect1> 33 <title>Arguments</title> 34 35 <variablelist> 36 <varlistentry> 37 <term><parameter>fd</parameter></term> 38 <listitem> 39 <para>&fd;</para> 40 </listitem> 41 </varlistentry> 42 <varlistentry> 43 <term><parameter>request</parameter></term> 44 <listitem> 45 <para>VIDIOC_G_CROP, VIDIOC_S_CROP</para> 46 </listitem> 47 </varlistentry> 48 <varlistentry> 49 <term><parameter>argp</parameter></term> 50 <listitem> 51 <para></para> 52 </listitem> 53 </varlistentry> 54 </variablelist> 55 </refsect1> 56 57 <refsect1> 58 <title>Description</title> 59 60 <para>To query the cropping rectangle size and position 61 applications set the <structfield>type</structfield> field of a 62 <structname>v4l2_crop</structname> structure to the respective buffer 63 (stream) type and call the <constant>VIDIOC_G_CROP</constant> ioctl 64 with a pointer to this structure. The driver fills the rest of the 65 structure or returns the &EINVAL; if cropping is not supported.</para> 66 67 <para>To change the cropping rectangle applications initialize the 68 <structfield>type</structfield> and &v4l2-rect; substructure named 69 <structfield>c</structfield> of a v4l2_crop structure and call the 70 <constant>VIDIOC_S_CROP</constant> ioctl with a pointer to this 71 structure.</para> 72 73 <para>Do not use the multiplanar buffer types. Use <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant> 74 instead of <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant> 75 and use <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> instead of 76 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>.</para> 77 78 <para>The driver first adjusts the requested dimensions against 79 hardware limits, &ie; the bounds given by the capture/output window, 80 and it rounds to the closest possible values of horizontal and 81 vertical offset, width and height. In particular the driver must round 82 the vertical offset of the cropping rectangle to frame lines modulo 83 two, such that the field order cannot be confused.</para> 84 85 <para>Second the driver adjusts the image size (the opposite 86 rectangle of the scaling process, source or target depending on the 87 data direction) to the closest size possible while maintaining the 88 current horizontal and vertical scaling factor.</para> 89 90 <para>Finally the driver programs the hardware with the actual 91 cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a 92 write-only ioctl, it does not return the actual parameters. To query 93 them applications must call <constant>VIDIOC_G_CROP</constant> and 94 &VIDIOC-G-FMT;. When the parameters are unsuitable the application may 95 modify the cropping or image parameters and repeat the cycle until 96 satisfactory parameters have been negotiated.</para> 97 98 <para>When cropping is not supported then no parameters are 99 changed and <constant>VIDIOC_S_CROP</constant> returns the 100 &EINVAL;.</para> 101 102 <table pgwide="1" frame="none" id="v4l2-crop"> 103 <title>struct <structname>v4l2_crop</structname></title> 104 <tgroup cols="3"> 105 &cs-str; 106 <tbody valign="top"> 107 <row> 108 <entry>__u32</entry> 109 <entry><structfield>type</structfield></entry> 110 <entry>Type of the data stream, set by the application. 111 Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, 112 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and 113 <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry> 114 </row> 115 <row> 116 <entry>&v4l2-rect;</entry> 117 <entry><structfield>c</structfield></entry> 118 <entry>Cropping rectangle. The same co-ordinate system as 119 for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry> 120 </row> 121 </tbody> 122 </tgroup> 123 </table> 124 </refsect1> 125 126 <refsect1> 127 &return-value; 128 </refsect1> 129 </refentry>
