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-.. Permission is granted to copy, distribute and/or modify this
-.. document under the terms of the GNU Free Documentation License,
-.. Version 1.1 or any later version published by the Free Software
-.. Foundation, with no Invariant Sections, no Front-Cover Texts
-.. and no Back-Cover Texts. A copy of the license is included at
-.. Documentation/media/uapi/fdl-appendix.rst.
-..
-.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
-
-********
-Examples
-********
-
-(A video capture device is assumed; change
-``V4L2_BUF_TYPE_VIDEO_CAPTURE`` for other devices; change target to
-``V4L2_SEL_TGT_COMPOSE_*`` family to configure composing area)
-
-Example: Resetting the cropping parameters
-==========================================
-
-.. code-block:: c
-
- struct v4l2_selection sel = {
- .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
- .target = V4L2_SEL_TGT_CROP_DEFAULT,
- };
- ret = ioctl(fd, VIDIOC_G_SELECTION, &sel);
- if (ret)
- exit(-1);
- sel.target = V4L2_SEL_TGT_CROP;
- ret = ioctl(fd, VIDIOC_S_SELECTION, &sel);
- if (ret)
- exit(-1);
-
-Setting a composing area on output of size of *at most* half of limit
-placed at a center of a display.
-
-Example: Simple downscaling
-===========================
-
-.. code-block:: c
-
- struct v4l2_selection sel = {
- .type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
- .target = V4L2_SEL_TGT_COMPOSE_BOUNDS,
- };
- struct v4l2_rect r;
-
- ret = ioctl(fd, VIDIOC_G_SELECTION, &sel);
- if (ret)
- exit(-1);
- /* setting smaller compose rectangle */
- r.width = sel.r.width / 2;
- r.height = sel.r.height / 2;
- r.left = sel.r.width / 4;
- r.top = sel.r.height / 4;
- sel.r = r;
- sel.target = V4L2_SEL_TGT_COMPOSE;
- sel.flags = V4L2_SEL_FLAG_LE;
- ret = ioctl(fd, VIDIOC_S_SELECTION, &sel);
- if (ret)
- exit(-1);
-
-A video output device is assumed; change ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
-for other devices
-
-Example: Querying for scaling factors
-=====================================
-
-.. code-block:: c
-
- struct v4l2_selection compose = {
- .type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
- .target = V4L2_SEL_TGT_COMPOSE,
- };
- struct v4l2_selection crop = {
- .type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
- .target = V4L2_SEL_TGT_CROP,
- };
- double hscale, vscale;
-
- ret = ioctl(fd, VIDIOC_G_SELECTION, &compose);
- if (ret)
- exit(-1);
- ret = ioctl(fd, VIDIOC_G_SELECTION, &crop);
- if (ret)
- exit(-1);
-
- /* computing scaling factors */
- hscale = (double)compose.r.width / crop.r.width;
- vscale = (double)compose.r.height / crop.r.height;