RGB Spectrum Quadra User's Guide - Manual (Page 96)

I M A G E C O N C E P T S
Positioning and Clipping
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• The size and shape of the source rectangle are independent of the
destination rectangle’s size and shape.
Suppose that you have defined an input’s source and destination rectangles so
that a 320 x 240 portion of a video source image is mapped into a 640 x 480
rectangle. Here, the destination rectangle is larger than the source rectangle, but
it has the same shape and the same width-to-height aspect ratio (4:3). Thus, the
original input image is enlarged (scaled) equally, in both dimensions.
Varying the destination rectangle’s size but preserving its aspect ratio makes the
displayed image larger or smaller. As long as its proportions correspond to
those of the source rectangle, the output image resembles the input image.
If you independently vary the shape of either the source or destination rectangle,
so that their aspect ratios are no longer the same, the displayed picture will
appear stretched or squeezed as compared to the original image.
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P O S I T I ON I N G A N D C L I P P IN G
An image can be sized and positioned anywhere on the output display. If the
destination rectangle is defined so that a portion is off the screen, that portion of
is “clipped” — until it is moved back into view.
Two examples of “image clipping” are illustrated below. In the first example,
the full size source rectangle (640 x 480) is mapped to a destination rectangle,
starting at (
900 , 100 ). The right-hand portion of the source image is clipped.
Figure A-5. Clipped Image, Screen Right