From: "Andreas Filsinger" <andreas@filsinger.de>
To: <efg2@efg2.com>
Subject: Computer Lab Feedback, "Image encrytion"
Date: Tuesday, October 31, 2000 8:42 AM

Earl,

i used the published "Image encryption"-Code to shrink it down to a
"form"-less simple all purpose Routine. I hope this helps others.
Thanks a lot for your unbelieveable Web-Output.

Mfg.A.Filsinger
(GERMANY)

procedure BMPScramble(b : TBitMap; Key : integer);
//
// (c)'00 by http://www.efg2.com/Lab
//
// scrambles (encrypt) a bitmap before you save it to
// disk (for example) or before post it to a database-field.
// Scramble it again before you want to view it.
// Ensure to use the same key-value, for each pic, but
// different values for different pictures.
//
var
 i,j               : integer;
 row               : pByteArray;
 ScanlineByteCount : integer;
begin
 with b do
 begin
  dormant; // ensure, that the image is a DIB
           // there where problems on monoChrome-BMPs,
           // the memory-image was not really what i expected
           // "dormant" seems to clear this.
  RandSeed := key;
  ScanlineByteCount := ABS(Integer(Scanline[1]) - Integer(Scanline[0]));
  FOR j := 0 TO pred(Height) DO
  BEGIN
   Row := Scanline[j];
   FOR i := 0 TO pred(ScanlineByteCount) DO
    Row[i]:= Row[i] XOR Random(256);
  END;
 end;
 randomize; // ensure, that future random-calls have true
            // random results
end;

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