/// <summary>
/// Clip a linestring.
/// </summary>
/// <param name="linestring">Linestrings that should be clipped.</param>
/// <param name="xmin">The minimum x of the clip rect.</param>
/// <param name="ymin">The minimum y of the clip rect.</param>
/// <param name="xmax">The maximum x of the clip rect.</param>
/// <param name="ymax">The maximum y of the clip rect.</param>
/// <returns> List of clipped linestrings.</returns>
public static List <List <double[]> > ClipLinestring(List <double[]> linestring, double xmin, double ymin, double xmax, double ymax)
{
List <List <double[]> > returnLinestrings = new List <List <double[]> >();
List <double[]> returnLinestring = new List <double[]>();
int numLines = linestring.Count - 1;
LineClipStatus prevClipStatus = LineClipStatus.Outside;
for (int lineNum = 0; lineNum < numLines; lineNum++)
{
double[] p0 = linestring[lineNum];
double[] p1 = linestring[lineNum + 1];
double x0 = p0[X];
double y0 = p0[Y];
double x1 = p1[X];
double y1 = p1[Y];
LineClipStatus clipStatus = ClipLine(ref x0, ref y0, ref x1, ref y1, xmin, ymin, xmax, ymax);
// See if we need to add no points, last point, or both points
if (clipStatus != LineClipStatus.Outside)
{
if (prevClipStatus == LineClipStatus.Outside || (prevClipStatus & LineClipStatus.ClippedLast) == LineClipStatus.ClippedLast)
{
// Add both
returnLinestring.Add(new[] { x0, y0 });
}
returnLinestring.Add(new[] { x1, y1 });
}
if ((clipStatus & LineClipStatus.ClippedLast) == LineClipStatus.ClippedLast)
{
returnLinestrings.Add(returnLinestring);
returnLinestring = new List <double[]>();
prevClipStatus = LineClipStatus.Outside;
}
else
{
prevClipStatus = clipStatus;
}
}
if (returnLinestring.Count > 1)
{
returnLinestrings.Add(returnLinestring);
}
return(returnLinestrings);
}
/// <summary>
/// Clip a line segment. Coordinates are modified in place.
/// </summary>
/// <param name="x1">The x value of the lines start point.</param>
/// <param name="y1">The y value of the lines start point.</param>
/// <param name="x2">The x value of the lines end point.</param>
/// <param name="y2">The y value of the lines end point.</param>
/// <param name="xmin">The minimum x of the clip rect.</param>
/// <param name="ymin">The minimum y of the clip rect.</param>
/// <param name="xmax">The maximum x of the clip rect.</param>
/// <param name="ymax">The maximum y of the clip rect.</param>
/// <returns> Clip status indicating how the line was clipped.</returns>
public static LineClipStatus ClipLine(ref double x1, ref double y1, ref double x2, ref double y2, double xmin, double ymin, double xmax, double ymax)
{
// Outcodes for P0, P1, and whatever point lies outside the clip rectangle
int hhh = 0;
bool done = false;
LineClipStatus returnValue = LineClipStatus.Unknown;
// compute outcodes
int outcode0 = ComputeOutCode(x1, y1, xmin, ymin, xmax, ymax);
int outcode1 = ComputeOutCode(x2, y2, xmin, ymin, xmax, ymax);
do
{
if ((outcode0 | outcode1) == 0)
{
if (returnValue == LineClipStatus.Unknown)
{
returnValue = LineClipStatus.Inside;
}
done = true;
}
else if ((outcode0 & outcode1) > 0)
{
returnValue = LineClipStatus.Outside;
done = true;
}
else
{
// failed both tests, so calculate the line segment to clip
// from an outside point to an intersection with clip edge
double x = 0, y = 0;
// At least one endpoint is outside the clip rectangle; pick it.
int outcodeOut;
if (outcode0 != 0)
{
outcodeOut = outcode0;
returnValue |= LineClipStatus.ClippedFirst;
}
else
{
outcodeOut = outcode1;
returnValue |= LineClipStatus.ClippedLast;
}
// Now find the intersection point;
// use formulas y = y0 + slope * (x - x0), x = x0 + (1/slope)* (y - y0)
if ((outcodeOut & Top) > 0)
{
x = x1 + ((x2 - x1) * (ymax - y1) / (y2 - y1));
y = ymax;
}
else if ((outcodeOut & Bottom) > 0)
{
x = x1 + ((x2 - x1) * (ymin - y1) / (y2 - y1));
y = ymin;
}
else if ((outcodeOut & Right) > 0)
{
y = y1 + ((y2 - y1) * (xmax - x1) / (x2 - x1));
x = xmax;
}
else if ((outcodeOut & Left) > 0)
{
y = y1 + ((y2 - y1) * (xmin - x1) / (x2 - x1));
x = xmin;
}
// Now we move outside point to intersection point to clip
// and get ready for next pass.
if (outcodeOut == outcode0)
{
x1 = x;
y1 = y;
outcode0 = ComputeOutCode(x1, y1, xmin, ymin, xmax, ymax);
}
else
{
x2 = x;
y2 = y;
outcode1 = ComputeOutCode(x2, y2, xmin, ymin, xmax, ymax);
}
}
hhh++;
}while (done != true && hhh < 5000);
return(returnValue);
}
