Here is an example of a routine to smooth a curve for display on the screen.
Its really an averager that creates points between the original points and uses those
new points to rearrange the old points to create a moving average of sorts. It does do
a very good job of smoothing out a set of data points on the screen.
It is also easily converted to other languages and is kind of fast enough for a brute force
approach to doing it.
The doonpaint() routine gives an example of a curve and the smoothing and shows the output
below the code.
{ This procedure smooths an array of x,y pairs of points. The
Smoothness parameter controls the iterations thru the routine.
3 times will usually do. The number of points required in the
array is the number of original points (Count) doubled for each
Smoothness time thru the loop. The array starts out filled with
Count points and the routine doubles the count each time through
the loop filling the array. First and last points are preserved.
Returns the new count. }
Type pPntArray=^PntArray; { Use with Smooth() }
PntArray=Array [0..0] of TPoint;
Function Smooth(pa:pPntArray; Count,Smoothness:Integer):Integer;
Var I,J,K,L,M:Integer;
r,r1:Real;
Begin
K:=0; L:=Count;
While K
M:=(L*2);
J:=M-1;
I:=L-1;
While J>0 do Begin
pa^[J]:=pa^[I];
If I>0 then Begin
r:=pa^[I-1].X+pa^[I].X;
r1:=pa^[I-1].Y+pa^[I].y;
pa^[J-1].X:=Round(r/2);
pa^[J-1].Y:=Round(r1/2);
end; {create a point}
If (M-J)>1 then Begin
r:=pa^[J+2].X+pa^[J+1].X;
r1:=pa^[J+2].Y+pa^[J+1].y;
pa^[J+1].X:=Round(r/2);
pa^[J+1].Y:=Round(r1/2);
r:=pa^[J].X+pa^[J+1].X;
r1:=pa^[J].Y+pa^[J+1].y;
pa^[J].X:=Round(r/2);
pa^[J].Y:=Round(r1/2);
end; {blend it in}
Dec(J,2); Dec(I);
end; {create points between}
L:=M;
Inc(K);
end; {smoothness}
Result:=L;
end; {smooth}
procedure TForm1.DoOnPaint(Sender: TObject);
Var ap:Array [0..25] of TPoint;
x,y,I,J,x1,y1,x2,y2,x3,y3,x4,y4,x5,y5,x6,y6:Integer;
final:Array [0..200] of TPoint;
scalex,scaley,r,r1,r2,m,b:Real;
count:Integer;
circs:Boolean;
Function Getx(xx:Integer):Integer;
Begin
r:=xx; r:=r*scalex;
Result:=Round(r);
end;
Function Gety(yy:Integer):Integer;
Begin
r:=yy; r:=r*scaley;
Result:=Round(r)-150;
end;
begin
scalex:=0.1; scaley:=0.1;
ap[0].x:=7000; ap[0].Y:=2000;
ap[1].x:=6500; ap[1].Y:=2000;
ap[2].x:=5959; ap[2].Y:=2250;
ap[3].x:=4915; ap[3].Y:=2500;
ap[4].x:=4134; ap[4].Y:=3500;
ap[5].x:=3562; ap[5].Y:=4250;
ap[6].x:=2616; ap[6].Y:=6000;
ap[7].x:=2242; ap[7].Y:=6600;
ap[8].x:=2000; ap[8].Y:=7000;
ap[9].x:=2000; ap[9].Y:=7000;
count:=10;
J:=1;
canvas.Pen.Color:=clred;
x:=Getx(ap[0].X);
y:=Gety(ap[0].Y);
canvas.MoveTo(x,y);
canvas.Ellipse(x-5,y-5,x+5,y+5);
While J
x:=Getx(ap[J].X);
y:=Gety(ap[J].Y);
canvas.LineTo(x,y);
canvas.Ellipse(x-5,y-5,x+5,y+5);
Inc(J);
end;
canvas.Pen.Color:=clblack;
J:=0;
While J
final[J].X:=ap[J].X;
final[J].Y:=ap[J].Y;
Inc(J);
end; {original points}
count:=Smooth(@final,10,3);
canvas.Pen.Color:=clblue;
J:=0;
x:=Getx(final[J].X);
y:=Gety(final[J].Y);
canvas.MoveTo(x,y);
canvas.Ellipse(x-5,y-5,x+5,y+5);
J:=1;
While J
x:=Getx(final[J].X);
y:=Gety(final[J].Y);
canvas.LineTo(x,y);
canvas.Ellipse(x-5,y-5,x+5,y+5);
Inc(J);
end;
canvas.Pen.Color:=clblack;
end;
Here's the code as plain text.