| .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
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| Introduction |
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| 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. |
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| 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. |
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| 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. |
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| 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. |
