anti-aliased line

				
!**************************************
! Name: anti-aliased line
! Description:draw an anti-aliased line using the Wu algorithm
! By: peter bone
!
! Inputs:A bitmap to draw the line on
End point coordinates of the line
Color of line
!
! Returns:the bitmap with an anti-aliased line drawn on it
!
!This code is copyrighted and has! limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=1425&lngWId=7!for details.!**************************************

type
 TRGB = record
r : byte;
g : byte;
b : byte;
 end;
 TRGBArray = array[0..32767] of TRGB;
 pRGBArray = ^TRGBArray;
 TScanlines = array of pRGBArray;
 TPointFloat = record
X : Real;
Y : Real;
 end;
Var
 Scanlines : TScanlines;
// create the scanlines array before calling wuline
Bmp := TBitmap.Create;
Bmp.PixelFormat := pf24bit;
Bmp.Width := 100; 
Bmp.Height := 100;
for y := 0 to 99 do Scanlines[y] := Bmp.Scanline[y];
// anti-aliased line. uses fixed point arithmetic
procedure T3DWorld.WuLine(x1, y1, x2, y2, W, H : integer ; R, G, B : byte);
var
 deltax, deltay, X, Y, start, finish : integer;
 LM, LR : integer;
 dxi, dyi, dydxi : integer;
begin
 deltax := abs(x2 - x1); // Calculate deltax and deltay for initialisation
 deltay := abs(y2 - y1);
 if (deltax = 0) or (deltay = 0) then begin
if SuperSample > 0 then begin
 SuperBmp.Canvas.Pen.Color := (B shl 16) + (G shl 8) + R;
 SuperBmp.Canvas.MoveTo(x1, y1);
 SuperBmp.Canvas.LineTo(x2, y2);
end else begin
 OffScrBmp.Canvas.Pen.Color := (B shl 16) + (G shl 8) + R;
 OffScrBmp.Canvas.MoveTo(x1, y1);
 OffScrBmp.Canvas.LineTo(x2, y2);
end;
exit;
 end;
 if deltax > deltay then begin // horizontal or vertical
if y2 > y1 then // determine rise and run
 dydxi := -deltay shl 16 div deltax
else
 dydxi := deltay shl 16 div deltax;
if x2 < x1 then begin
 start := x2; // right to left
 finish := x1;
 dyi := y2 shl 16;
end else begin
 start := x1; // left to right
 finish := x2;
 dyi := y1 shl 16;
 dydxi := -dydxi; // inverse slope
end;
if finish >= W then finish := W - 1;
for X := start to finish do begin
 Y := dyi shr 16;
 if (X < 0) or (Y < 0) or (Y > H-2) then begin
Inc(dyi, dydxi);
Continue;
 end;
 LM := dyi - Y shl 16; // fractional part of dyi - in fixed-point
 LR := 65536 - LM;
 Scanlines[Y][X].B := (B*LR + Scanlines[Y][X].B*LM) shr 16;
 Scanlines[Y][X].G := (G*LR + Scanlines[Y][X].G*LM) shr 16;
 Scanlines[Y][X].R := (R*LR + Scanlines[Y][X].R*LM) shr 16;
 Inc(Y);
 Scanlines[Y][X].B := (B*LM + Scanlines[Y][X].B*LR) shr 16;
 Scanlines[Y][X].G := (G*LM + Scanlines[Y][X].G*LR) shr 16;
 Scanlines[Y][X].R := (R*LM + Scanlines[Y][X].R*LR) shr 16;
 Inc(dyi, dydxi); // next point
end;
 end else begin
if x2 > x1 then // determine rise and run
 dydxi := -deltax shl 16 div deltay
else
 dydxi := deltax shl 16 div deltay;
if y2 < y1 then begin
 start := y2; // right to left
 finish := y1;
 dxi := x2 shl 16;
end else begin
 start := y1; // left to right
 finish := y2;
 dxi := x1 shl 16;
 dydxi := -dydxi; // inverse slope
end;
if finish >= H then finish := H - 1;
for Y := start to finish do begin
 X := dxi shr 16;
 if (Y < 0) or (X < 0) or (X > W-2) then begin
Inc(dxi, dydxi);
Continue;
 end;
 LM := dxi - X shl 16;
 LR := 65536 - LM;
 Scanlines[Y][X].B := (B*LR + Scanlines[Y][X].B*LM) shr 16;
 Scanlines[Y][X].G := (G*LR + Scanlines[Y][X].G*LM) shr 16;
 Scanlines[Y][X].R := (R*LR + Scanlines[Y][X].R*LM) shr 16;
 Inc(X);
 Scanlines[Y][X].B := (B*LM + Scanlines[Y][X].B*LR) shr 16;
 Scanlines[Y][X].G := (G*LM + Scanlines[Y][X].G*LR) shr 16;
 Scanlines[Y][X].R := (R*LM + Scanlines[Y][X].R*LR) shr 16;
 Inc(dxi, dydxi); // next point
end;
 end;
end;