http://blog.csdn.net/cwpoint/article/details/6438668

uses WinINet;

Function TForm1.GetCacheVerifyCodeFile(VerifyCodeURL:String; Var CacheVerifyCodeFile:String):Boolean;
Var
lpEntryInfo: PInternetCacheEntryInfo;
dwEntrySize, dwLastError, Hwd: LongWORD; 
i, j: Integer; 
f: String;
Begin
Result := false; 
dwEntrySize := 0; 
j := 0; 
CacheVerifyCodeFile := ''; 
FindFirstUrlCacheEntry(Nil, TInternetCacheEntryInfo(Nil^), dwEntrySize); 
GetMem(lpEntryInfo, dwEntrySize); 
Hwd := FindFirstUrlCacheEntry(Nil, lpEntryInfo^, dwEntrySize); 
If Hwd <> 0 Then 
Begin 
    Repeat 
      dwEntrySize := 0; 
      FindNextUrlCacheEntry(Hwd, TInternetCacheEntryInfo(Nil^), dwEntrySize); 
      dwLastError := GetLastError(); 
      If dwLastError = ERROR_INSUFFICIENT_BUFFER Then 
      Begin 
        GetMem(lpEntryInfo, dwEntrySize);
        If FindNextUrlCacheEntry(Hwd, lpEntryInfo^, dwEntrySize) Then
        begin
          If Pos(UpperCase(VerifyCodeURL), UpperCase(lpEntryInfo.lpszSourceUrlName)) > 0 Then
          Begin
            i := FileAge(lpEntryInfo.lpszLocalFileName);
            If i > j Then
            Begin
              j := i;
              f := lpEntryInfo.lpszLocalFileName;
            End
            Else
              DeleteUrlCacheEntry(lpEntryInfo.lpszSourceUrlName);
          End;
        end;
      End;
      Application.ProcessMessages;
    Until (dwLastError = ERROR_NO_MORE_ITEMS);

    If FileExists(f) Then 
    Begin 
      CacheVerifyCodeFile := f;
      Result := true; 
    End; 
End;
FreeMem(lpEntryInfo);
FindCloseUrlCache(Hwd);
End;

可用于在缓存中的验证码图片，或者防盗链的图片的采集，嘿嘿。

此函数有两个参数，第一个是网络图片地址，第二个是本地缓存地址。第二个作为输出端口。

http://www.cnblogs.com/toosuo/archive/2010/09/02/1815583.html