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 61applications 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 64with a pointer to this structure. The driver fills the rest of the 65structure 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 71structure.</para> 72 73 <para>The driver first adjusts the requested dimensions against 74hardware limits, &ie; the bounds given by the capture/output window, 75and it rounds to the closest possible values of horizontal and 76vertical offset, width and height. In particular the driver must round 77the vertical offset of the cropping rectangle to frame lines modulo 78two, such that the field order cannot be confused.</para> 79 80 <para>Second the driver adjusts the image size (the opposite 81rectangle of the scaling process, source or target depending on the 82data direction) to the closest size possible while maintaining the 83current horizontal and vertical scaling factor.</para> 84 85 <para>Finally the driver programs the hardware with the actual 86cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a 87write-only ioctl, it does not return the actual parameters. To query 88them applications must call <constant>VIDIOC_G_CROP</constant> and 89&VIDIOC-G-FMT;. When the parameters are unsuitable the application may 90modify the cropping or image parameters and repeat the cycle until 91satisfactory parameters have been negotiated.</para> 92 93 <para>When cropping is not supported then no parameters are 94changed and <constant>VIDIOC_S_CROP</constant> returns the 95&EINVAL;.</para> 96 97 <table pgwide="1" frame="none" id="v4l2-crop"> 98 <title>struct <structname>v4l2_crop</structname></title> 99 <tgroup cols="3"> 100 &cs-str; 101 <tbody valign="top"> 102 <row> 103 <entry>__u32</entry> 104 <entry><structfield>type</structfield></entry> 105 <entry>Type of the data stream, set by the application. 106Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, 107<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and 108<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry> 109 </row> 110 <row> 111 <entry>&v4l2-rect;</entry> 112 <entry><structfield>c</structfield></entry> 113 <entry>Cropping rectangle. The same co-ordinate system as 114for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry> 115 </row> 116 </tbody> 117 </tgroup> 118 </table> 119 </refsect1> 120 121 <refsect1> 122 &return-value; 123 </refsect1> 124</refentry> 125