| .. 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 |
| |
| ************ |
| 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. |
