各位好!我也是专门用Delphi开发GIS/GPS系统的,特来此一游,和大家一起学习学习!请各位帮我看看两个小问题。 (50分)

  • 主题发起人 主题发起人 aizb
  • 开始时间 开始时间
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aizb

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GUEST, unregistred user!
1、CreatePolygonRgn API函数在Win2K/Delphi下为什么总是返回0,在Win2K/VC中又正常。
2、有没有计算两个指定点数组形成的区域的交集区域的点数组的函数。
 
1,请参考
http://www.itaz.com/edgetracer/irregular_windows_delphi.htm
2,想计算裁剪对吧
等晚上我回家后发上来。
 
2,
procedure GetClipRgn(GeoRect : TGeoRect;var BufList : TList;
ShpType : integer);
var
I,Side : integer; {Side指定剪切边的左、上、右、下}
TempList : TList;
PP : PGeoPoint;
XX,YY :do
uble;

X1,Y1,X2,Y2 :do
uble;
Accepted : Boolean;
BufPArray : PXYArray;
IsFirstPointCalc : Integer; //第一点是否是求出来的,1:初始值,2:原来链表值,3:求出的值
begin

for Side := 1 to 4do
begin

TempList := BufList;
BufList := TList.Create;

Accepted := FALSE;
IsFirstPointCalc := 1;
for I := 0 to TempList.Count - 1do
begin

//判断点是否该被取得}
Case Side of
1 : begin

Accepted := PGeoPoint(TempList.Items)^.X > GeoRect.Left;
end;

2 : begin

Accepted := PGeoPoint(TempList.Items)^.Y > GeoRect.Top;
end;

3 : begin

Accepted := PGeoPoint(TempList.Items)^.X < GeoRect.Right;
end;

4 : begin

Accepted := PGeoPoint(TempList.Items)^.Y < GeoRect.Bottom;
end;

end;


if Accepted then
begin

GetMem(PP,SizeOf(TGeoPoint));
PP^.X := PGeoPoint(TempList.Items)^.X;
PP^.Y := PGeoPoint(TempList.Items)^.Y;
BufList.Add(PP);
if IsFirstPointCalc = 1 then
IsFirstPointCalc := 2;
end;


if I < TempList.Count - 1 then
begin

case Side of
1 : begin
{左}
X1 := GeoRect.Left; Y1 := GeoRect.Top;
X2 := GeoRect.Left; Y2 := GeoRect.Bottom;
end;

2 : begin
{上}
X1 := GeoRect.Left; Y1 := GeoRect.Top;
X2 := GeoRect.Right; Y2 := GeoRect.Top;
end;

3 : begin
{右}
X1 := GeoRect.Right; Y1 := GeoRect.Top;
X2 := GeoRect.Right; Y2 := GeoRect.Bottom;
end;

4 : begin

X1 := GeoRect.Left; Y1 := GeoRect.Bottom;
X2 := GeoRect.Right; Y2 := GeoRect.Bottom;
end;

end;


if GetIntersectedPoint(X1,Y1,X2,Y2,PGeoPoint(TempList.Items)^.X,PGeoPoint(TempList.Items)^.Y,PGeoPoint(TempList.Items[I+1])^.X,PGeoPoint(TempList.Items[I+1])^.Y,XX,YY,2) then
begin

GetMem(PP,SizeOf(TGeoPoint));
PP^.X := XX;
PP^.Y := YY;
BufList.Add(PP);
if IsFirstPointCalc = 1 then
IsFirstPointCalc := 3;
end;

end
else
begin

//将多边形封闭}
if ShpType = 3 then
begin

if (BufList.Count > 0) and (IsFirstPointCalc = 3) then
begin

GetMem(PP,SizeOf(TGeoPoint));
PP^.X := PGeoPoint(BufList.Items[0])^.X;
PP^.Y := PGeoPoint(BufList.Items[0])^.Y;
BufList.Add(PP);
end;

end;

end;

end;
{for I}

for I := 0 to TempList.Count - 1do
begin

FreeMem(TempList.Items,SizeOf(TGeoPoint));
end;

TempList.Free;
end;
{for Side}
//test
if BufList.Count < 0 then

ShowMessage('Error 3!');
//
end;


//获得X1,Y1,X2,Y2的交点,无交点时返回FALSE,Flag为1时交点必须位于两个矩形交叉区域内,Flag为2时交点为广义交点,即直线的延长线有效
//注意:Flag为2时前四个参数一定为剪切线}
function GetIntersectedPoint(X1,Y1,X2,Y2,X3,Y3,X4,Y4 :do
uble;var XX,YY :do
uble;Flag : integer):Boolean;
var
K1,K2,B1,B2 :do
uble; {二条直线的斜率}
V1,V2 : Boolean; {有斜率为无穷大的线存在}
// V1,V2 : integer; {1 :初始值,2:TRUE, 3 : FALSE}
begin

//X1,Y1,X2,Y2 为第一条直线,X3,Y3,X4,Y4 为第二条直线}
V1 := FALSE;
V2 := FALSE;

K1 := 1.7 * 10e308;
K2 := 5 * 10 - 324;
B1 := K1;
B2 := K2;
if Abs(X2-X1)>0.00000000001 then
begin

K1 := (Y2-Y1)/(X2-X1);
B1 := Y1-K1*X1;
end
else
begin

XX := X1;
V1 := TRUE;
end;


if Abs(X4-X3)>0.00000000001 then
begin

K2 := (Y4-Y3)/(X4-X3);
B2 := Y3-K2*X3;
end
else
begin

XX := X3;
V2 := TRUE;
end;



if (Abs(K1 - K2) < 0.000000000000001) or (V1 and V2) then
begin

Result := FALSE;
Exit;
end;


if (not V1) and (not V2) then
begin

XX := (B1-B2)/(K2-K1);
YY := K1*XX+B1;
end
else
if V2 then
begin

YY := K1*XX+B1;
end else
begin

YY := K2*XX+B2;
end;


if Flag = 1 then
begin

//如果计算出来的交点位于两个矩形的公共区域,则为真交点}
if (IsPtInRect(XX,YY,X1,Y1,X2,Y2)) and (IsPtInRect(XX,YY,X3,Y3,X4,Y4)) then

result := TRUE
else

result := FALSE;
end
else

if Flag = 2 then
begin

if (IsPtInRect(XX,YY,X3,Y3,X4,Y4)) then

result := TRUE
else

result := FALSE;
end;

end;



//TList的成员指针为以下类型
PGeoPoint = ^TGeoPoint;
TGeoPoint = record
X,Y :do
uble;
end;



 
谢谢吕雪松:
1、你给的例子是静态点数组,没有问题,可我的是动态数组,在Win2k中有问题,但这个问题已经搞定。
2、我试试!给分了,不多,别见笑!
 
我的是矩形裁剪多边形的程序,你可以稍微改改成为多边形裁剪多边形:
把以下程序改为一个多边形边的遍历就可以了。


case Side of
1 : begin
{左}
X1 := GeoRect.Left; Y1 := GeoRect.Top;
X2 := GeoRect.Left; Y2 := GeoRect.Bottom;
end;

2 : begin
{上}
X1 := GeoRect.Left; Y1 := GeoRect.Top;
X2 := GeoRect.Right; Y2 := GeoRect.Top;
end;

3 : begin
{右}
X1 := GeoRect ...
 

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