下面是我写的关于线段的一个类,给出两端点,可以动态绘制出该线段.
type
TLine=class //y=ax+b
private
FLineStyle
Horizontal,Vertical,Diagonal);
FPoints:array of TPoint;
FStartPoint:TPoint; //开始端点
FEndPoint:TPoint; //结束端点
FPointCount,FFactPointCount:Integer;
FA,FB
ouble; //a,b参数
FInterval:Integer;
function GetSpace(P1,P2:TPoint):Integer;
function GetLength:Integer;
procedure CalcAB;
procedure CalcPoints;
function OnLine(P:TPoint):Boolean;
public
constructor Create;overload;
constructor Create(AStartPoint,AEndPoint:TPoint;APointCount:Integer);overload;
destructor Destroy;override;
procedure Draw(ACanvas:TCanvas);
property StartPoint:TPoint read FStartPoint write FStartPoint;
property EndPoint:TPoint read FEndPoint write FEndPoint;
property PointCount:Integer read FPointCount write FPointCount;
property Length:Integer read GetLength;
Property Interval:Integer read FInterval write FInterval;
end;
implementation
constructor TLine.Create;
begin
FInterval:=10;
end;
constructor TLine.Create(AStartPoint,AEndPoint:TPoint;APointCount:Integer);
begin
FStartPoint:=AStartPoint;
FEndPoint:=AEndPoint;
FPointCount:=APointCount;
FInterval:=10;
end;
destructor TLine.Destroy;
begin
SetLength(FPoints,0);
inherited;
end;
procedure TLine.CalcAB; //求a,b参数
begin
if (FEndPoint.X-FStartPoint.X) =0 then
begin
FA:=0;
FB:=FStartPoint.X;
FLineStyle:=Vertical;
end else
if (FEndPoint.Y-FStartPoint.Y) =0 then
begin
FA:=0;
FB:=FStartPoint.Y;
FLineStyle:=Horizontal;
end else
begin
FA:=(FEndPoint.Y-FStartPoint.Y)/(FEndPoint.X-FStartPoint.X);
FB:=FStartPoint.Y-FA*FStartPoint.X;
FLineStyle:=Diagonal;
end;
end;
function TLine.GetSpace(P1,P2:TPoint): Integer; //两点间距离
begin
Result:=Round(Sqrt(Sqr(P2.X-P1.X)+Sqr(P2.Y-P1.Y)));
end;
function TLine.GetLength: Integer; //线段长度
begin
Result:=GetSpace(FStartPoint,FEndPoint);
end;
function TLine.OnLine(P:TPoint): Boolean; //某点是否在线段上
begin
if (GetSpace(FStartPoint,P)<Length) and (GetSpace(FEndPoint,P)<Length) then
Result:=True
else
Result:=False;
end;
procedure TLine.CalcPoints; //选取线上的一些点
var
I:Integer;
PerLength
ouble;
X,Y:Integer;
FlagX,FlagY:Integer;
begin
SetLength(FPoints,FPointCount);
PerLength:=Length/(FPointCount-1); //所选点间的距离
FFactPointCount:=0;
FPoints[0]:=FStartPoint;
Inc(FFactPointCount);
if FStartPoint.X>FEndPoint.X then FlagX:=-1 else FlagX:=1;
if FStartPoint.Y>FEndPoint.Y then FlagY:=-1 else FlagY:=1;
for I:=1 to FPointCount-3 do
begin
if FLineStyle=Vertical then //竖线
begin
X:=Round(FB);
Y:=Round(PerLength*I)*FlagY+FStartPoint.Y;
end else
if FLineStyle=Horizontal then //横线
begin
X:=Round(PerLength*I)*FlagX+FStartPoint.X;
Y:=Round(FB);
end else
begin //斜线
X:=Round(PerLength*I)*FlagX+FStartPoint.X;
Y:=Round(FA*X+FB);
end;
if OnLine(Point(X,Y)) then
begin
FPoints[FFactPointCount]:=Point(X,Y);
Inc(FFactPointCount);
end;
end;
FPoints[FFactPointCount]:=FEndPoint;
Inc(FFactPointCount);
SetLength(FPoints,FFactPointCount);
end;
procedure TLine.Draw(ACanvas: TCanvas); //动态绘制该直线
var
I:Integer;
begin
CalcAB;
CalcPoints;
with ACanvas do
begin
Pen.Color:=clRed;
for I:=0 to FFactPointCount-2 do
begin
Sleep(Interval); //延时
MoveTo(FPoints
.X,FPoints.Y);
LineTo(FPoints[I+1].X,FPoints[I+1].Y);
end;
end;
end;
