13229Spst.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 23229Spst 33229Spst************ 418471SwoschIntroduction 550476Speter************ 63229Spst 73229SpstSome video capture devices can sample a subsection of a picture and 83229Spstshrink or enlarge it to an image of arbitrary size. Next, the devices 93229Spstcan insert the image into larger one. Some video output devices can crop 103229Spstpart of an input image, scale it up or down and insert it at an 113229Spstarbitrary scan line and horizontal offset into a video signal. We call 123229Spstthese abilities cropping, scaling and composing. 133229Spst 143229SpstOn a video *capture* device the source is a video signal, and the 153229Spstcropping target determine the area actually sampled. The sink is an 163229Spstimage stored in a memory buffer. The composing area specifies which part 173229Spstof the buffer is actually written to by the hardware. 183229Spst 193229SpstOn a video *output* device the source is an image in a memory buffer, 203229Spstand the cropping target is a part of an image to be shown on a display. 213229SpstThe sink is the display or the graphics screen. The application may 2213572Spstselect the part of display where the image should be displayed. The size 2313572Spstand position of such a window is controlled by the compose target. 2413572Spst 2513572SpstRectangles for all cropping and composing targets are defined even if 2613572Spstthe device does supports neither cropping nor composing. Their size and 273229Spstposition will be fixed in such a case. If the device does not support 283229Spstscaling then the cropping and composing rectangles have the same size. 2913572Spst