/// <summary>
/// This function converts a polygon shapefile to grid. It implements the line-scan algorithm.
/// <param name="PolySf">The polygon shapefile</param>
/// <param name="FldID">The field index</param>
/// <param name="Newgrd">File name of the new grid</param>
/// <param name="header">Header object of the new grid</param>
/// <param name="writePxDeleg">Delegate function for writing the grid pixels</param>
/// <param name="nodatavalue">'no data' value</param>
/// <param name="cback">can be used to report progress (optional)</param>
/// <returns>true if successful</returns>
//
// AUTHOR NAME: Enrico A. Chiaradia
// FROM: University of Milan (Italy)
// e.mail: [email protected]
//
// For details about the line-scan algorithm,
// please refer to http://www.profc.udec.cl/~gabriel/tutoriales/giswb/vol1/cp3/cp3-6.htm
//
// for each shape in PolySf
// 0) get the shape value (in the shapefile table)
// 1) load all the borders in a matrix composed by x(startpoint), x(endpoint), slope and share
// 2) define x of first scan line
// for each scan lines
// 3) calculate intersections with polygon border
// 4) sort intersections from lower Y to the higther
// 5) convert line space between two consecutive intersection to raster
private bool Poly2Grid(MapWinGIS.Shapefile PolySf, int FldID, MapWinGIS.Grid Newgrd,
MapWinGIS.GridHeader header, MapWinGIS.GridDataType grType,
MapWinGIS.ICallback cback)
{
double xMin, xMax;
double x0, x1, x2, y0, y1, y2, m, q;
int nShps, nVs, i, s, nP, p, tempn, v, b;
object val;
bool flg;
bord brd; //struct to keep a border
System.Collections.ArrayList bordi2; //list of borders
int perc = 1; //percent shapes done
int shpsPerc;
MapWinGIS.Shape PolyShp; //the polygon shape
//count the number of shapes
nShps = PolySf.NumShapes;
shpsPerc = NumPercentShapes(perc, nShps); //percent of progress
for( s = 0; s < nShps; ++s )
{
//for each shape, determine the extent and the number of parts
i = 0;
PolyShp = PolySf.get_Shape(s);
nP = PolyShp.NumParts;
xMin = PolyShp.Extents.xMin;
//yMin = PolyShp.Extents.yMin;
xMax = PolyShp.Extents.xMax;
//yMax = PolyShp.Extents.yMax;
//exclude shapes which are completely outside of the grid extents
if (!IsGridContainsShape(PolyShp, header))
{
continue;
}
//return the shape's value
val = GetCellValue(PolySf, FldID, s, header.NodataValue);
//load polygon borders
nVs = PolyShp.numPoints - 1;
bordi2 = new System.Collections.ArrayList(nVs + 1);
b = -1;
tempn = 0;
for( p = 0; p < nP; ++p )
{
x0 = PolyShp.get_Point(tempn).x;
y0 = PolyShp.get_Point(tempn).y;
for( v = tempn; v < nVs; ++v )
{
x1 = PolyShp.get_Point(v).x;
x2 = PolyShp.get_Point(v + 1).x;
y1 = PolyShp.get_Point(v).y;
y2 = PolyShp.get_Point(v + 1).y;
if (x1 != x2) // no vertical lines
{
m = (y2 - y1) / (x2 - x1);
q = y1 - (m * x1);
//add border to the list
b = b + 1;
brd = new bord();
brd.x1 = x1;
brd.x2 = x2;
brd.m = m;
brd.q = q;
bordi2.Add(brd);
}
//in case of multi-parts polygon
if( (x2 == x0) && (y2 == y0) )
{
tempn = v + 2;
break;
}
} //Next v
} // next p
//define the first line-scan
double xstart;
// 20 nov 07 added by Enrico A. Chiaradia
//necessary if grid extentions differ from shapefile extentions
if ( xMin >= header.XllCenter )
{
xstart = FirstLineXY(xMin, header.XllCenter, header.dX, 1);
}
else
{
xstart = FirstLineXY(xMin, header.XllCenter, header.dX, -1);
}
// the list of intersection y-values
System.Collections.ArrayList y_int = new System.Collections.ArrayList();
System.Collections.ArrayList pixels = new System.Collections.ArrayList();
do
{
flg = Interseca(bordi2, y_int, xstart);
flg = SortArray(y_int);
flg = ScanLine2(y_int, xstart, ref pixels, ref Newgrd, header, val, cback);
xstart = xstart + header.dX;
}
while ( xstart <= xMax );
writePxList(Newgrd, grType, pixels, val, cback);
//report the progress
if (s >= shpsPerc)
{
reportProgress(shpsPerc, nShps, "shapefile to grid", cback);
perc = (int)( (s * 100) / nShps );
shpsPerc = NumPercentShapes(perc + 1, nShps);
}
} // next shape
reportProgress(100, 100, "shapefile to grid", cback); //100 % shapes done
return true;
}
private bool Multipoint2Grid(MapWinGIS.Shapefile MultipointSf, int FldID, MapWinGIS.Grid Newgrd,
MapWinGIS.GridHeader header, MapWinGIS.GridDataType grType, MapWinGIS.ICallback cback)
{
//count the number of shapes
int s, p;
MapWinGIS.Shape shp;
MapWinGIS.Point pt;
ArrayList pixels = new ArrayList();
object val;
GridPixel px;
int nShps = MultipointSf.NumShapes;
int nPts = 0;
int perc = 1;
int shpsPerc = NumPercentShapes(perc, nShps); //percent of progress
for (s = 0; s < nShps; ++s)
{
//get the shape
shp = MultipointSf.get_Shape(s);
//exclude shapes which are completely outside of the grid extents
if (!IsGridContainsShape(shp, header))
{
continue;
}
//get the shape's value
val = GetCellValue(MultipointSf, FldID, s, header.NodataValue);
nPts = shp.numPoints;
for (p = 0; p < nPts; ++p)
{
//write pixel values
pt = shp.get_Point(p);
Newgrd.ProjToCell(pt.x, pt.y, out px.col, out px.row);
pixels.Add(px);
writePxList(Newgrd, grType, pixels, val, cback);
}
//report the progress
if (s >= shpsPerc)
{
reportProgress(shpsPerc, nShps, "shapefile to grid", cback);
perc = (int)((s * 100) / nShps);
shpsPerc = NumPercentShapes(perc + 1, nShps);
}
}
return true;
}
/// <summary>
/// convert point shapefile to grid
/// </summary>
private bool Point2Grid(MapWinGIS.Shapefile PointSf, int FldID, MapWinGIS.Grid Newgrd,
MapWinGIS.GridHeader header, MapWinGIS.GridDataType grType, MapWinGIS.ICallback cback)
{
//count the number of shapes
int s;
MapWinGIS.Shape shp;
MapWinGIS.Point pt = new MapWinGIS.Point();
object val;
GridPixel px;
int nShps = PointSf.NumShapes;
int perc = 1;
int shpsPerc = NumPercentShapes(perc, nShps); //percent of progress
for (s = 0; s < nShps; ++s)
{
//get the point
shp = PointSf.get_Shape(s);
//exclude shapes which are completely outside of the grid extents
if (!IsGridContainsShape(shp, header))
{
continue;
}
if (shp.numPoints > 0)
{
pt = shp.get_Point(0);
if (pt != null)
{
//return the shape's value and write the pixel
val = GetCellValue(PointSf, FldID, s, header.NodataValue);
Newgrd.ProjToCell(pt.x, pt.y, out px.col, out px.row);
writePx(Newgrd, grType, px, val, cback);
}
}
//report the progress
if (s >= shpsPerc)
{
perc = (int)((s * 100) / nShps);
shpsPerc = NumPercentShapes(perc + 1, nShps);
reportProgress(shpsPerc, nShps, "shapefile to grid", cback);
}
}
return true;
}
/// <summary>
/// converts a Line shapefile to grid using Bresenham algorithm
/// </summary>
/// <param name="PolySf">Polygon shapefile object</param>
/// <param name="FldID">Field index</param>
/// <param name="Newgrd">New grid object</param>
/// <param name="header">Grid header</param>
/// <param name="nodatavalue"></param>
/// <param name="cback">optional, for reporting progress</param>
/// <returns>true if successful</returns>
private bool Line2Grid(MapWinGIS.Shapefile LineSf, int FldID, MapWinGIS.Grid Newgrd,
MapWinGIS.GridHeader header, MapWinGIS.GridDataType grType, MapWinGIS.ICallback cback)
{
int numParts, numPoints;
int curPartStart, curPartEnd, vertexCol, vertexRow, lastCol, lastRow;
int nShps = LineSf.NumShapes;
int perc = 1;
int shpsPerc = NumPercentShapes(perc, nShps); //percent of progress
int s = 0; //shape number
int p = 0; //part number
int k = 0; //point number
MapWinGIS.Shape LineShp = new MapWinGIS.Shape();
MapWinGIS.Point curPoint;
//Rasterization ras = new Rasterization(); //rasterization class, contains the code of
//lineToGrid methods independent on MapWinGIS functions
ArrayList vertices = new ArrayList(); //list of line vertex points
ArrayList pixels = new ArrayList(); //list of calculated pixels on the line
GridPixel px;
object val; //the shape's value
for (s = 0; s < nShps; ++s)
{
LineShp = LineSf.get_Shape(s);
numParts = LineShp.NumParts;
numPoints = LineShp.numPoints;
//exclude shapes which are completely outside of the grid extents
if (!IsGridContainsShape(LineShp, header))
{
continue;
}
//get the shape's value
val = GetCellValue(LineSf, FldID, s, header.NodataValue);
//process each part of the polyline
curPartStart = 0;
for (p = 0; p < numParts; ++p)
{
vertices.Clear();
pixels.Clear();
curPartStart = LineShp.get_Part(p);
// check for multi-part lines
if (p < numParts - 1)
{
curPartEnd = LineShp.get_Part(p + 1) - 1;
}
else
{
curPartEnd = numPoints - 1;
}
//go to next part if there's zero points
if (numPoints <= 0)
{
continue;
}
// add all points of current part to rasterization list
// always add the first point of the part (convert its coordinates to
// grid row and column)
curPoint = LineShp.get_Point(curPartStart);
Newgrd.ProjToCell(curPoint.x, curPoint.y,
out vertexCol, out vertexRow);
px.col = vertexCol;
px.row = vertexRow;
vertices.Add(px);
lastCol = vertexCol; lastRow = vertexRow;
// add all other points with different grid coordinates
for (k = curPartStart + 1; k <= curPartEnd; ++k)
{
// (check if it has a different row or column than the previous point)
curPoint = LineShp.get_Point(k);
Newgrd.ProjToCell(curPoint.x, curPoint.y,
out vertexCol, out vertexRow);
if (vertexCol != lastCol || vertexRow != lastRow)
{
px.col = vertexCol;
px.row = vertexRow;
vertices.Add(px);
lastCol = vertexCol;
lastRow = vertexRow;
}
}
// convert the polyline and write pixels to grid
LineBresenham(vertices, pixels);
writePxList(Newgrd, grType, pixels, val, cback);
}
//report the progress
if (s >= shpsPerc)
{
reportProgress(shpsPerc, nShps, "shapefile to grid", cback);
perc = (int)((s * 100) / nShps);
shpsPerc = NumPercentShapes(perc + 1, nShps);
}
}
return true;
}
