ID Number: Q83807
3.00 3.10
WINDOWS
Summary:
SYMPTOMS
When the CreateEllipticRgn function is used to create a region in
the shape of an ellipse and the Ellipse function is called with the
same parameters to draw an ellipse on the screen, the calculated
region does not match the drawn ellipse identically.
CAUSE
The Ellipse function includes the lower-right point of the bounding
rectangle in its calculations, while the CreateEllipticRgn function
excludes the lower-right point.
RESOLUTION
To draw a filled ellipse on the screen that matches an elliptic
region, create the region with the CreateEllipticRgn function and
call the FillRgn function to fill the region with the currently
selected brush.
More Information:
The region created by the CreateEllipticRgn is slightly smaller than
the elliptical area created by Ellipse. Unfortunately, decreasing the
width and height of the bounding rectangle by 1 pixel does not solve
the problem. Although changing the parameters of the Ellipse function
in this way produces a smaller ellipse, the new ellipse does not match
the region created with CreateEllipticRgn.
Additional reference words: 3.00 3.10