Delphi ActiveX Requires Chilkat v11.7.0+

QR Code Error Correction Levels

See more QR Code Examples

Demonstrates the four QR error-correction levels. L, M, Q and H allow a reader to recover the data when about 7%, 15%, 25% and 30% of the symbol is damaged or covered. More error correction leaves less room for data, so the same text needs a larger symbol at a higher level. The default is M. The example also shows boostErrorCorrection, which raises the level for free when the chosen version has room to spare. Delphi ActiveX

var
success: Integer;
fmt: TChilkatFormats;
json: TChilkatJsonObject;
jsonOut: TChilkatJsonObject;
levels: TChilkatJsonArray;
i: Integer;
json2: TChilkatJsonObject;

begin
success := 0;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

fmt := TChilkatFormats.Create(Self);
json := TChilkatJsonObject.Create(Self);
jsonOut := TChilkatJsonObject.Create(Self);
json.UpdateString('payload.text','https://www.chilkatsoft.com/barcode_overview.asp');

//  Encode the same text at each level.
levels := TChilkatJsonArray.Create(Self);
levels.Load('["L","M","Q","H"]');

for i := 0 to 3 do
  begin
    json.UpdateString('encoding.qr.errorCorrection',levels.StringAt(i));
    success := fmt.QrCode('generate',json.ControlInterface,jsonOut.ControlInterface);
    if (success = 0) then
      begin
        Memo1.Lines.Add(fmt.LastErrorText);
        Exit;
      end;
    Memo1.Lines.Add('level ' + levels.StringAt(i) + ': version ' + IntToStr(jsonOut.IntOf('symbols[0].selectedEncoding.version')) + ', ' + IntToStr(jsonOut.IntOf('symbols[0].dimensions.modulesWide'))
         + ' modules wide');
  end;

//  The four symbols.  They hold the same text, and the higher the level, the larger the symbol:

//  

//  A symbol often has room left over.  boostErrorCorrection uses it: the level is raised
//  as far as the same version allows, so the symbol is no larger but is more robust.
json2 := TChilkatJsonObject.Create(Self);
json2.UpdateString('payload.text','https://chilkatsoft.com');
json2.UpdateString('encoding.qr.errorCorrection','L');
success := fmt.QrCode('generate',json2.ControlInterface,jsonOut.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(fmt.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add('level L requested: version ' + IntToStr(jsonOut.IntOf('symbols[0].selectedEncoding.version')) + ', level ' + jsonOut.StringOf('symbols[0].selectedEncoding.errorCorrection'));

json2.UpdateBool('encoding.qr.boostErrorCorrection',1);
success := fmt.QrCode('generate',json2.ControlInterface,jsonOut.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(fmt.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add('level L with boost: version ' + IntToStr(jsonOut.IntOf('symbols[0].selectedEncoding.version')) + ', level ' + jsonOut.StringOf('symbols[0].selectedEncoding.errorCorrection'));

//  Level L, and level M reached by the boost.  The two symbols are the same size:

//  

//  Sample output:

//  level L: version 3, 29 modules wide
//  level M: version 4, 33 modules wide
//  level Q: version 5, 37 modules wide
//  level H: version 6, 41 modules wide
//  level L requested: version 2, level L
//  level L with boost: version 2, level M