PPMD String Compression

Demonstrates string compression using PPMD.

Download Chilkat Compression ActiveX

uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, StdCtrls,
    CHILKATCOMPRESSIONLib_TLB,
    OleCtrls;

...

procedure TForm1.Button1Click(Sender: TObject);
var
compress: TChilkatCompression;
success: Integer;
strData: String;
i: Integer;
compressedStr: String;
strOriginal: String;

begin
compress := TChilkatCompression.Create(Self);

//  Any string argument automatically begins a 30-day trial.
success := compress.UnlockComponent('30-day trial');
if (success <> 1) then
  begin
    ShowMessage('Compression component unlock failed');
    Exit;
  end;

compress.Algorithm := 'ppmd';

//  Create a long string to compress.
strData := 'abcdefg1122334455667788';
strData := strData + #13#10;
for i := 0 to 99 do
  begin
    strData := strData + 'abcdefg1122334455667788';
    strData := strData + #13#10;
  end;

//  Depending on the programming language, the string
//  may be Unicode.  Tell the component to convert to
//  ansi (1-byte/char) prior to compression:
compress.Charset := 'ansi';

//  Compressed data is binary, meaning that all byte values
//  from 0 to 255 are possible.  The result would not be
//  a printable string.  To receive a printable string (us-ascii),
//  the resultant compressed data should be encoded using
//  an encoding such as base64.  Set the EncodingMode
//  property to determine the output encoding:
//  (Valid choices are "base64", "hex", "url", and others)
compress.EncodingMode := 'base64';

//  Note: Base64 encoding expands the compressed data by
//  4/3rds because each 3 bytes of binary data are represented
//  by 4 printable chars.  Hex, for example, doubles the output
//  size because each byte is represented by 2 printable chars.

//  PPMD compress the string:

compressedStr := compress.CompressStringENC(strData);
if (compressedStr = NULL ) then
  begin
    ShowMessage(compress.LastErrorText);
    Exit;
  end;

//  Display the compressed string.
//  The result will be:
//  ec8YZ5vk9za18d0plwuV7R65em9OZge9gJXht/QAAAAAAAAAABNOZQAAKw==
Memo1.Lines.Add(compressedStr);

//  Decompress back to the original:

strOriginal := compress.DecompressStringENC(compressedStr);

//  Display the uncompressed original:
Memo1.Lines.Add('--- Original ---');
Memo1.Lines.Add(strOriginal);
end;