需要引用 ShlwApi.pas

//取绝对路径的函数

// BasePath: 是参考路径。RelativePath: 是指相对路径

function GetAbsolutePathEx(BasePath, RelativePath:string):string;
var
Dest:array [0..MAX_PATH] of char;
begin
FillChar(Dest,MAX_PATH+1,0);
PathCombine(Dest,PChar(BasePath), PChar(RelativePath));
Result:=string(Dest);
end;


示范：

S := GetAbsolutePath('C:\Windows\System32', '..\DEMO.TXT')

// S 将得到 'C:\Windows\DEMO.TXT

//绝对路径转换为相对路径的函数


function GetRelativePath(const Path, AFile: string): string;

function GetAttr(IsDir: Boolean): DWORD;
begin
if IsDir then
Result := FILE_ATTRIBUTE_DIRECTORY
else
Result := FILE_ATTRIBUTE_NORMAL;
end;

var
p: array[0..MAX_PATH] of Char;
begin
PathRelativePathTo(p, PChar(Path), GetAttr(False), PChar(AFile), GetAttr(True));
Result := StrPas(p);
end;