The following example creates an elliptical
path and draws that
path with a narrow black pen. Then the code tests each point in an array to see whether the point lies in the interior of the
path. Points that lie in the interior are painted green, and points that do not lie in the interior are painted red.
C++
VOID IsVisibleExample(HDC hdc)
{
Graphics graphics(hdc);
INT j;
Pen blackPen(Color(255, 0, 0, 0), 1);
SolidBrush brush(Color(255, 255, 0, 0));
// Create and draw a path.
GraphicsPath path;
path.AddEllipse(50, 50, 200, 100);
graphics.DrawPath(&blackPen, &path);
// Create an array of four points, and determine whether each
// point in the array touches the outline of the path.
// If a point touches the outline, paint it green.
// If a point does not touch the outline, paint it red.
PointF[] = {
PointF(50, 100),
PointF(250, 100),
PointF(150, 170),
PointF(180, 60)};
for(j = 0; j <= 3; ++j)
{
if(path.IsVisible(points[j].X, points[j].Y, &graphics))
brush.SetColor(Color(255, 0, 255, 0));
else
brush.SetColor(Color(255, 255, 0, 0));
graphics.FillEllipse(&brush, points[j].X - 3.0f, points[j].Y - 3.0f, 6.0f, 6.0f);
}
}
SUB GDIP_IsVisiblePoint (BYVAL hdc AS DWORD)
LOCAL hStatus AS LONG
LOCAL pGraphics AS DWORD
LOCAL pPath AS DWORD
LOCAL pBlackPen AS DWORD
LOCAL pBrush AS DWORD
DIM pts(3) AS POINTF
LOCAL result AS LONG
LOCAL i AS LONG
hStatus = GdipCreateFromHDC(hdc, pGraphics)
hStatus = GdipCreatePen1(GDIP_ARGB(255, 255, 255, 0), 1, %UnitWorld, pBlackPen)
hStatus = GdipCreateSolidFill(GDIP_ARGB(255, 255, 0, 0), pBrush)
' // Create and draw a path.
hStatus = GdipCreatePath(%FillModeAlternate, pPath)
hStatus = GdipAddPathEllipse(pPath, 50, 50, 200, 100)
hStatus = GdipDrawPath(pGraphics, pBlackPen, pPath)
' // Create an array of four points, and determine whether each
' // point in the array touches the outline of the path.
' // If a point touches the outline, paint it green.
' // If a point does not touch the outline, paint it red.
pts(0).x = 50 : pts(0).y = 100
pts(1).x = 250 : pts(1).y = 100
pts(2).x = 150 : pts(2).y = 170
pts(3).x = 180 : pts(3).y = 60
FOR i = 0 TO 3
hStatus = GdipIsVisiblePathPoint(pPath, pts(i).x, pts(i).y, pGraphics, result)
IF result THEN
hStatus = GdipSetSolidFillColor(pBrush, GDIP_ARGB(255, 0, 255, 0))
ELSE
hStatus = GdipSetSolidFillColor(pBrush, GDIP_ARGB(255, 255, 0, 0))
END IF
hStatus = GdipFillEllipse(pGraphics, pBrush, pts(i).x - 3, pts(i).y - 3, 6, 6)
NEXT
' // Cleanup
IF pBlackPen THEN GdipDeletePen(pBlackPen)
IF pPath THEN GdipDeletePath(pPath)
IF pGraphics THEN GdipDeleteGraphics(pGraphics)
END SUB
(http://www.jose.it-berater.org/captures/GdipIsVisiblePathPoint.png)