1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4************ 5Introduction 6************ 7 8Some video capture devices can sample a subsection of a picture and 9shrink or enlarge it to an image of arbitrary size. Next, the devices 10can insert the image into larger one. Some video output devices can crop 11part of an input image, scale it up or down and insert it at an 12arbitrary scan line and horizontal offset into a video signal. We call 13these abilities cropping, scaling and composing. 14 15On a video *capture* device the source is a video signal, and the 16cropping target determine the area actually sampled. The sink is an 17image stored in a memory buffer. The composing area specifies which part 18of the buffer is actually written to by the hardware. 19 20On a video *output* device the source is an image in a memory buffer, 21and the cropping target is a part of an image to be shown on a display. 22The sink is the display or the graphics screen. The application may 23select the part of display where the image should be displayed. The size 24and position of such a window is controlled by the compose target. 25 26Rectangles for all cropping and composing targets are defined even if 27the device does supports neither cropping nor composing. Their size and 28position will be fixed in such a case. If the device does not support 29scaling then the cropping and composing rectangles have the same size. 30