1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10************ 11Introduction 12************ 13 14Some video capture devices can sample a subsection of a picture and 15shrink or enlarge it to an image of arbitrary size. Next, the devices 16can insert the image into larger one. Some video output devices can crop 17part of an input image, scale it up or down and insert it at an 18arbitrary scan line and horizontal offset into a video signal. We call 19these abilities cropping, scaling and composing. 20 21On a video *capture* device the source is a video signal, and the 22cropping target determine the area actually sampled. The sink is an 23image stored in a memory buffer. The composing area specifies which part 24of the buffer is actually written to by the hardware. 25 26On a video *output* device the source is an image in a memory buffer, 27and the cropping target is a part of an image to be shown on a display. 28The sink is the display or the graphics screen. The application may 29select the part of display where the image should be displayed. The size 30and position of such a window is controlled by the compose target. 31 32Rectangles for all cropping and composing targets are defined even if 33the device does supports neither cropping nor composing. Their size and 34position will be fixed in such a case. If the device does not support 35scaling then the cropping and composing rectangles have the same size. 36