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| >Video for Linux Two API Specification: Revision 0.24</TH |
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| ><TR |
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| ><H1 |
| ><A |
| NAME="VIDIOC-G-CROP" |
| ></A |
| >ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN9998" |
| ></A |
| ><H2 |
| >Name</H2 |
| >VIDIOC_G_CROP, VIDIOC_S_CROP -- Get or set the current cropping rectangle</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN10002" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN10003" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, struct v4l2_crop *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><P |
| ></P |
| ><A |
| NAME="AEN10013" |
| ></A |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int ioctl</CODE |
| >(int fd, int request, const struct v4l2_crop *argp);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN10023" |
| ></A |
| ><H2 |
| >Arguments</H2 |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >fd</CODE |
| ></DT |
| ><DD |
| ><P |
| >File descriptor returned by <A |
| HREF="r14090.htm" |
| ><CODE |
| CLASS="FUNCTION" |
| >open()</CODE |
| ></A |
| >.</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >request</CODE |
| ></DT |
| ><DD |
| ><P |
| >VIDIOC_G_CROP, VIDIOC_S_CROP</P |
| ></DD |
| ><DT |
| ><CODE |
| CLASS="PARAMETER" |
| >argp</CODE |
| ></DT |
| ><DD |
| ><P |
| ></P |
| ></DD |
| ></DL |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN10043" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >To query the cropping rectangle size and position |
| applications set the <CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| > field of a |
| <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_crop</CODE |
| > structure to the respective buffer |
| (stream) type and call the <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CROP</CODE |
| > ioctl |
| with a pointer to this structure. The driver fills the rest of the |
| structure or returns the <SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| > error code if cropping is not supported.</P |
| ><P |
| >To change the cropping rectangle applications initialize the |
| <CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| > and struct <A |
| HREF="x6570.htm#V4L2-RECT" |
| >v4l2_rect</A |
| > substructure named |
| <CODE |
| CLASS="STRUCTFIELD" |
| >c</CODE |
| > of a v4l2_crop structure and call the |
| <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_S_CROP</CODE |
| > ioctl with a pointer to this |
| structure.</P |
| ><P |
| >The driver first adjusts the requested dimensions against |
| hardware limits, i. e. 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.</P |
| ><P |
| >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.</P |
| ><P |
| >Finally the driver programs the hardware with the actual |
| cropping and image parameters. <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_S_CROP</CODE |
| > is a |
| write-only ioctl, it does not return the actual parameters. To query |
| them applications must call <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_CROP</CODE |
| > and |
| <A |
| HREF="r10944.htm" |
| ><CODE |
| CLASS="CONSTANT" |
| >VIDIOC_G_FMT</CODE |
| ></A |
| >. When the parameters are unsuitable the application may |
| modify the cropping or image parameters and repeat the cycle until |
| satisfactory parameters have been negotiated.</P |
| ><P |
| >When cropping is not supported then no parameters are |
| changed and <CODE |
| CLASS="CONSTANT" |
| >VIDIOC_S_CROP</CODE |
| > returns the |
| <SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| > error code.</P |
| ><DIV |
| CLASS="TABLE" |
| ><A |
| NAME="V4L2-CROP" |
| ></A |
| ><P |
| ><B |
| >Table 1. struct <CODE |
| CLASS="STRUCTNAME" |
| >v4l2_crop</CODE |
| ></B |
| ></P |
| ><TABLE |
| BORDER="0" |
| FRAME="void" |
| WIDTH="100%" |
| CLASS="CALSTABLE" |
| ><COL |
| WIDTH="25%" |
| TITLE="C1"><COL |
| WIDTH="25%" |
| TITLE="C2"><COL |
| WIDTH="50%" |
| TITLE="C3"><TBODY |
| VALIGN="TOP" |
| ><TR |
| ><TD |
| >enum <A |
| HREF="x5953.htm#V4L2-BUF-TYPE" |
| >v4l2_buf_type</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >type</CODE |
| ></TD |
| ><TD |
| >Type of the data stream, set by the application. |
| Only these types are valid here: <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_VIDEO_CAPTURE</CODE |
| >, |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_VIDEO_OUTPUT</CODE |
| >, |
| <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_VIDEO_OVERLAY</CODE |
| >, and custom (driver |
| defined) types with code <CODE |
| CLASS="CONSTANT" |
| >V4L2_BUF_TYPE_PRIVATE</CODE |
| > |
| and higher.</TD |
| ></TR |
| ><TR |
| ><TD |
| >struct <A |
| HREF="x6570.htm#V4L2-RECT" |
| >v4l2_rect</A |
| ></TD |
| ><TD |
| ><CODE |
| CLASS="STRUCTFIELD" |
| >c</CODE |
| ></TD |
| ><TD |
| >Cropping rectangle. The same co-ordinate system as |
| for struct <A |
| HREF="r7771.htm#V4L2-CROPCAP" |
| >v4l2_cropcap</A |
| > <CODE |
| CLASS="STRUCTFIELD" |
| >bounds</CODE |
| > is used.</TD |
| ></TR |
| ></TBODY |
| ></TABLE |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN10092" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >On success <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > is returned, on error <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > and the <CODE |
| CLASS="VARNAME" |
| >errno</CODE |
| > variable is set appropriately:</P |
| ><P |
| ></P |
| ><DIV |
| CLASS="VARIABLELIST" |
| ><DL |
| ><DT |
| ><SPAN |
| CLASS="ERRORCODE" |
| >EINVAL</SPAN |
| ></DT |
| ><DD |
| ><P |
| >Cropping is not supported.</P |
| ></DD |
| ></DL |
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