| Markus Heiser | 5377d91 | 2016-06-30 15:18:56 +0200 | [diff] [blame] | 1 | .. -*- coding: utf-8; mode: rst -*- |
| 2 | |
| 3 | ******** |
| 4 | Examples |
| 5 | ******** |
| 6 | |
| 7 | (A video capture device is assumed; change |
| 8 | ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` for other devices; change target to |
| 9 | ``V4L2_SEL_TGT_COMPOSE_*`` family to configure composing area) |
| 10 | |
| 11 | |
| 12 | .. code-block:: c |
| 13 | |
| 14 | struct v4l2_selection sel = { |
| 15 | .type = V4L2_BUF_TYPE_VIDEO_CAPTURE, |
| 16 | .target = V4L2_SEL_TGT_CROP_DEFAULT, |
| 17 | }; |
| 18 | ret = ioctl(fd, VIDIOC_G_SELECTION, &sel); |
| 19 | if (ret) |
| 20 | exit(-1); |
| 21 | sel.target = V4L2_SEL_TGT_CROP; |
| 22 | ret = ioctl(fd, VIDIOC_S_SELECTION, &sel); |
| 23 | if (ret) |
| 24 | exit(-1); |
| 25 | |
| 26 | Setting a composing area on output of size of *at most* half of limit |
| 27 | placed at a center of a display. |
| 28 | |
| 29 | |
| 30 | .. code-block:: c |
| 31 | |
| 32 | struct v4l2_selection sel = { |
| 33 | .type = V4L2_BUF_TYPE_VIDEO_OUTPUT, |
| 34 | .target = V4L2_SEL_TGT_COMPOSE_BOUNDS, |
| 35 | }; |
| 36 | struct v4l2_rect r; |
| 37 | |
| 38 | ret = ioctl(fd, VIDIOC_G_SELECTION, &sel); |
| 39 | if (ret) |
| 40 | exit(-1); |
| 41 | /* setting smaller compose rectangle */ |
| 42 | r.width = sel.r.width / 2; |
| 43 | r.height = sel.r.height / 2; |
| 44 | r.left = sel.r.width / 4; |
| 45 | r.top = sel.r.height / 4; |
| 46 | sel.r = r; |
| 47 | sel.target = V4L2_SEL_TGT_COMPOSE; |
| 48 | sel.flags = V4L2_SEL_FLAG_LE; |
| 49 | ret = ioctl(fd, VIDIOC_S_SELECTION, &sel); |
| 50 | if (ret) |
| 51 | exit(-1); |
| 52 | |
| 53 | A video output device is assumed; change ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` |
| 54 | for other devices |
| 55 | |
| 56 | |
| 57 | .. code-block:: c |
| 58 | |
| 59 | struct v4l2_selection compose = { |
| 60 | .type = V4L2_BUF_TYPE_VIDEO_OUTPUT, |
| 61 | .target = V4L2_SEL_TGT_COMPOSE, |
| 62 | }; |
| 63 | struct v4l2_selection crop = { |
| 64 | .type = V4L2_BUF_TYPE_VIDEO_OUTPUT, |
| 65 | .target = V4L2_SEL_TGT_CROP, |
| 66 | }; |
| 67 | double hscale, vscale; |
| 68 | |
| 69 | ret = ioctl(fd, VIDIOC_G_SELECTION, &compose); |
| 70 | if (ret) |
| 71 | exit(-1); |
| 72 | ret = ioctl(fd, VIDIOC_G_SELECTION, &crop); |
| 73 | if (ret) |
| 74 | exit(-1); |
| 75 | |
| 76 | /* computing scaling factors */ |
| 77 | hscale = (double)compose.r.width / crop.r.width; |
| 78 | vscale = (double)compose.r.height / crop.r.height; |
| 79 | |
| 80 | |
| 81 | |
| 82 | |
| 83 | .. ------------------------------------------------------------------------------ |
| 84 | .. This file was automatically converted from DocBook-XML with the dbxml |
| 85 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes |
| 86 | .. from the linux kernel, refer to: |
| 87 | .. |
| 88 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook |
| 89 | .. ------------------------------------------------------------------------------ |