How to add increasing number to saved files in Delphi?

Question

I'm making a program that takes a snapshot of the screen, and saves it to a folder as a Bitmap picture. I seem to be running into a problem though, the picture just overwrites itself.

Can anyone tell me how I can make it so when it saves, the number will be one higher than the last? For example: Save 1: Screenshot0001.bmp Save 2: Screenshot0002.bmp Save 3: Screenshot0003.bmp

And so on.

Answer 1

At program startup, iterate all Screenshot*.bmp files, parse out the numeric part and find the highest - assign this value to your counter. When doing a snapshot, go into a loop that tries crreating Screenshot.bmp with "only create if doesn't exist already" (CREATE_NEW) semantics, incrementing the counter until you find an unused name.

Alternately, use timestamp instead of counter :)

Answer 2

There are many ways to accomplish something like this.

1. Do it like your digital camera does; Have a counter and save it in a file or in the registry. You'll probably run into multi-user problems and you'll still have to handle situations where an image already exists.

2. Don't use a incrementing number, but write a datetime in the filename. FileName := 'Screenshot_'+FormatDateTime('yyyymmdd-hhnnss-zzz.bmp',now());

3. Do something like the code below to find the latest number. I think this does what you're describing, but remember that this code will get slower as you write more images. With thousands of pictures and a slow drive or network it could 'hang' your program.

..

i := 0;
while FileExists(Format('%sScreenshot%.04d.bmp',[ImgPath,i])) do
  inc(i);

Answer 3

You need a routine like this which mimics Windows file duplication where the first file is 'My File', the second is 'My File (2)', then 'My File (3)' etc.

function AppendDuplicationNumber( const AStr : string ) : string;
// Used to make strings unique
// This examines the string AStr for trailing '(n)' where
// 'n' is an integer.
// If the (n) part is found, n is incremented, otherwise '(2)' is
// appended to the string.
var
  iLH, iRH, I : integer;
  S           : string;
begin
  Result := AStr;
  iLH    := CharPosBackwards( '(', Result );
  If iLH > 0 then
    begin
    iRH := PosEx( ')', Result, iLH );
    If iRH > 0 then
      begin
      I := StrToIntDef( Copy( Result, iLH+1, iRH-iLH-1 ), 0 );
      If I > 0 then
        begin
        Inc(I);
        S := IntToStr( I );
        Delete( Result, iLH+1, iRH-iLH-1 );
        Insert( S, Result, iLH+1 );
        Exit;
        end;
      end;
    end;

  // Did not increment existing (n), so append it.
  Result := Result + ' (2)';
end;