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DynaPDF Manual - Page 61

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Path Painting and Construction
Page 61 of 750
For a path composed of two concentric circles, the areas enclosed by both circles are considered
to be inside, provided that both are drawn in the same direction. If the circles are drawn in
opposite directions, only the "doughnut" shape between them is inside, according to the rule;
the "doughnut hole" is outside (the draw direction for closed shapes can be changed with the
property Get/SetDrawDirection()).
Even-Odd Rule
An alternative to the nonzero winding number rule is the even-odd rule. This rule determines
the "insideness" of a point by drawing a ray from that point in any direction and simply
counting the number of path segments that cross the ray. If this number is odd, the point is
inside; if even, the point is outside. This yields the same results as the nonzero winding number
rule for paths with simple shapes, but produces different results for more complex shapes.
The Figure below shows the effects of applying the even-odd rule to complex paths. For the
five-pointed star, the rule considers the triangular points to be inside the path, but not the
pentagon in the center. For the two concentric circles, only the "doughnut" shape between the
two circles is considered inside, regardless of the directions in which the circles are drawn.
The rules described above are applied on vector graphics and clipping paths. DynaPDF
supports three basic functions to fill, stroke, or to mark a given path as clipping path. A clipping
path can in turn be filled, stroked, or both.
The basic path operating functions are:
ClosePath() and ClipPath() support a large set of path painting operators. Let us take a look at
the available path painting constants:
typedef enum
// Nonzero Winding Number Rule

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