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Amtec
May 14, 2004, 11:48:06
Does anyone know of a way of changing the aspect ratio used by the OverlayBitmap?

I need to overlay a graphic circle over a live video picture of a circle. Unfortunatly, due to the lenses used, the video circle is distorted - more of an egg and I need to match the two

Any ideas?

Many thanks

Steve

Stefan Geissler
May 17, 2004, 09:17:12
Hello Steve,

The aspect ratio of the OverlayBitmap can not be changed, because it has every time the same ratio as the video format has. To solve your problem, you must draw an ellipse (see Windows API help). The ellipse is drawn by specifiying a rectangle. This can be used to compensate the lens aspect ration problem.
The (C) declaration of the ellipse is:

BOOL Ellipse(
HDC hdc, // handle to device context
int nLeftRect, // x-coord of bounding rectangle's upper-left corner
int nTopRect, // y-coord of bounding rectangle's upper-left corner
int nRightRect, // x-coord of bounding rectangle's lower-right corner
int nBottomRect // y-coord of bounding rectangle's lower-right corner
);

This this thread http://www.theimagingsourceforums.com/showthread.php?s=&threadid=315618&highlight=Ellipse
to see all declaration for Visual Basic.