Home Script Language Particles Various Helper Routines CalcEdgePath
See also: CreateEdgeOfParticle 

CalcEdgePath

Declaration: CalcEdgePath (EdgeMat: TInt2DArray; AnchorX, AnchorY: integer; var EdgePath: TPDblArray): integer;
The function CalcEdgePath calculates the polynomial along the edge of a region. The edge has to be specified in the matrix EdgeMat. The edge pixels are represented by non-zero values. The parameters AnchorX and AnchorY define the coordinates of an arbitrary pixel of the edge. The variable parameter EdgePath returns the polygon path. Please note that the returned polygon distinguishes between the left and the right part (or the upper and lower part) of a pixel. Left and bottom parts of a pixel are indicated by and offset of 0.25, right and top parts by 0.75.

The function returns the number of vertices of the found polygon.

Sample Program: The following short example creates an artificial region and calculates its polygonal shape along the edge of this region: 
program ParticleEdgeVector;

const
  PAGE = 1;

var
  i, j       : integer;
  Region     : TInt2Darray;
  EdgePixels : TInt2Darray;
  Anchorx    : integer;
  AnchorY    : integer;
  EdgePath   : TPDblArray;

begin
ResizeIntMatrix (region, 30,30);
FillIntMatrix(region,0);
Region[1][9] := 1;      // define the particle
Region[2][9] := 1;
Region[2][8] := 1;
Region[2][7] := 1;
Region[1][7] := 1;
Region[3][8] := 1;
Region[3][9] := 1;
Region[3][10] := 1;
Region[2][11] := 1;
Region[3][11] := 1;
Region[4][11] := 1;
Region[3][7] := 1;
Region[4][9] := 1;
Region[4][8] := 1;
Region[4][7] := 1;
Region[5][9] := 1;
Region[5][8] := 1;
Region[6][8] := 1;
Region[7][9] := 1;
Region[7][8] := 1;
Region[7][7] := 1;
Region[3][6] := 1;
Region[4][6] := 1;
Region[5][6] := 1;
Region[4][5] := 1;
Region[5][5] := 1;
Region[4][4] := 1;
Region[4][3] := 1;
                     // create the edge
CreateEdgeOfParticle (1,Region,EdgePixels, anchorx, anchory);
                     // calculate the edge polygon
CalcEdgePath (EdgePixels, AnchorX, AnchorY, EdgePath);

                     // display the results
ChartBook.Reset;
ChartBook.TabCaption[PAGE] := 'Edge';
ChartBook.Configure
   (PAGE,               // page 1
    true, true, false,  // only chart and table are visible
    250, 250);          // default width & height
ChartBook.TabCaption[PAGE] := 'Cross Section';
with ChartBook.Charts[PAGE] do
  begin
  Reset;
  DataColor := clBlack;      // indicate edge pixels
  for i:=1 to length(Region) do
    for j:=1 to length(Region[0]) do
      if Region[i-1][j-1] = 0
        then MarkAt (i-1, j-1, 0)
        else MarkAt (i-1, j-1,26);
  DataColor := clRed;        // draw polygon
  MoveTo (EdgePath[0].x,EdgePath[0].y);
  for i:=1 to length(EdgePath) do
    DrawTo (EdgePath[i-1].x,EdgePath[i-1].y);
  AutoRange (1,4);
  Update;
  end;

with ChartBook.Tables[PAGE] do
  begin                    // list the polygon
  SuppressPaint := true;
  Clear;
  NrOfRows := length(EdgePath);
  Header[1] := 'X';
  Header[2] := 'Y';
  for i:=1 to length(EdgePath) do
    begin
    Elem [1,i] := strff(EdgePath[i-1].x,1,2);
    Elem [2,i] := strff(EdgePath[i-1].y,1,2);
    end;
  SuppressPaint := false;
  end;
end.