Lazarus Pascal

Decode Base64 Image String (GIF, JPG, etc.) and Save to File

I have an XML response that includes a base 64 encoded image string (UPS label). It's a huge string and I need to save it as a gif file on my users pc.

This example shows how to do it..

Lazarus Pascal

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.BinData,
  Chilkat.Xml;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  bd: TBinData;
  x: string;
  xml: TXml;
  gifBase64: string;

begin
  success := False;

  bd := TBinData.Create;

  //  I created an extra-small GIF image for this example..
  success := bd.LoadFile('qa_data/gif/xsmall.gif');
  if (success <> True) then
    begin
      WriteLn('Failed to load GIF image file.');
      Exit;
    end;

  //  Show GIF bytes as base64:
  WriteLn(bd.GetEncoded('base64'));

  //  This particular GIF in base64 is this:
  //  R0lGODlhBQAFAMQAAAAAAP////z8/PHx8evr6+jo6OHh4d7e3sPDw8LCwpqamo2NjWxsbGRkZFpaWk1NTUtLS0hISCwsLCQkJP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAEAABQALAAAAAAFAAUAAAUTYCAYQUBAU1lI0TIgztE8jFImIQA7

  //  Let's begin with an XML string:
  x := '<abc><def>R0lGODlhBQAFAMQAAAAAAP////z8/PHx8evr6+jo6OHh4d7e3sPDw8LCwpqamo2NjWxsbGRkZFpaWk1NTUtLS0hISCwsLCQkJP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAEAABQALAAAAAAFAAUAAAUTYCAYQUBAU1lI0TIgztE8jFImIQA7</def></abc>';

  xml := TXml.Create;
  success := xml.LoadXml(x);

  //  Get the base64 string:
  gifBase64 := xml.GetChildContent('def');

  WriteLn(gifBase64);

  //  Load bd with the base64 decoded bytes.  
  bd.Clear();
  bd.AppendEncoded(gifBase64,'base64');

  //  Save to a GIF file.
  success := bd.WriteFile('qa_output/xsmall.gif');


  bd.Free;
  xml.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.