Автор: http://www.swissdelphicenter.ch

{ 
  This tip show, how to get the filesize, width, height, bitcount and color used 
  from a bitmap. 

  Dieses Beispiel zeigt, wie man Dateigrosse, breite, hohe, Farbtiefe und Farbanzahl 
  von einem Bitmap ausliest. 
}


 procedure TForm1.Button1Click(Sender: TObject);
 var
   fileheader: TBitmapfileheader;
   infoheader: TBitmapinfoheader;
   s: TFilestream;
 begin
   s := TFileStream.Create('c:\YourBitmap.bmp', fmOpenRead);
   try
     s.Read(fileheader, SizeOf(fileheader));
     s.Read(infoheader, SizeOf(infoheader));
   finally
     s.Free;
   end;
   listbox1.Items.Clear;
   listbox1.Items.Add('Filesize:    ' + IntToStr(fileheader.bfSize));
   listbox1.Items.Add('Width:       ' + IntToStr(infoheader.biWidth));
   listbox1.Items.Add('Height:      ' + IntToStr(infoheader.biHeight));
   listbox1.Items.Add('BitCount:    ' + IntToStr(infoheader.biBitCount));
   listbox1.Items.Add('Used:        ' + IntToStr(infoheader.biClrUsed));
 end;

 { 
  BitCount: 
  1 = black/white 
  4 = 16 colors 
  8 = 256 colors 
}