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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>The driver first adjusts the requested dimensions against | |
74 | hardware limits, &ie; the bounds given by the capture/output window, | |
75 | and it rounds to the closest possible values of horizontal and | |
76 | vertical offset, width and height. In particular the driver must round | |
77 | the vertical offset of the cropping rectangle to frame lines modulo | |
78 | two, such that the field order cannot be confused.</para> | |
79 | ||
80 | <para>Second the driver adjusts the image size (the opposite | |
81 | rectangle of the scaling process, source or target depending on the | |
82 | data direction) to the closest size possible while maintaining the | |
83 | current horizontal and vertical scaling factor.</para> | |
84 | ||
85 | <para>Finally the driver programs the hardware with the actual | |
86 | cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a | |
87 | write-only ioctl, it does not return the actual parameters. To query | |
88 | them applications must call <constant>VIDIOC_G_CROP</constant> and | |
89 | &VIDIOC-G-FMT;. When the parameters are unsuitable the application may | |
90 | modify the cropping or image parameters and repeat the cycle until | |
91 | satisfactory parameters have been negotiated.</para> | |
92 | ||
93 | <para>When cropping is not supported then no parameters are | |
94 | changed 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> | |
6016af82 | 103 | <entry>__u32</entry> |
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104 | <entry><structfield>type</structfield></entry> |
105 | <entry>Type of the data stream, set by the application. | |
106 | Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, | |
9495356f HV |
107 | <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and |
108 | <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry> | |
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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 | |
114 | for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry> | |
115 | </row> | |
116 | </tbody> | |
117 | </tgroup> | |
118 | </table> | |
119 | </refsect1> | |
120 | ||
121 | <refsect1> | |
122 | &return-value; | |
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123 | </refsect1> |
124 | </refentry> |