| 1234567891011121314151617181920212223242526272829 |
- .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
- .. c:namespace:: V4L
- ************
- Introduction
- ************
- Some video capture devices can sample a subsection of a picture and
- shrink or enlarge it to an image of arbitrary size. Next, the devices
- can insert the image into larger one. Some video output devices can crop
- part of an input image, scale it up or down and insert it at an
- arbitrary scan line and horizontal offset into a video signal. We call
- these abilities cropping, scaling and composing.
- On a video *capture* device the source is a video signal, and the
- cropping target determine the area actually sampled. The sink is an
- image stored in a memory buffer. The composing area specifies which part
- of the buffer is actually written to by the hardware.
- On a video *output* device the source is an image in a memory buffer,
- and the cropping target is a part of an image to be shown on a display.
- The sink is the display or the graphics screen. The application may
- select the part of display where the image should be displayed. The size
- and position of such a window is controlled by the compose target.
- Rectangles for all cropping and composing targets are defined even if
- the device does supports neither cropping nor composing. Their size and
- position will be fixed in such a case. If the device does not support
- scaling then the cropping and composing rectangles have the same size.
|
