How to activate flash light in camera to help barcode reading

[Mika_Koistinen]

HI,
Is there a method to active rear camera light with TWebCamera to help barcode reading ?

[Tunde (Tünde Keller)]

Hi,

TWebCamera does not have such functionality by default. It's not exactly clear how widely the torch constraint is supported, which could be used to activate and deactivate the phone's flash.

We did a small test but in our case we were not able to turn off the flash after activating it (it might not be an issue for you if you stop the camera right after reading a barcode). It is most likely related to this bug report: 1246938 - chromium - An open-source project to help move the web forward. - Monorail

You can try the following and see if it works for your use case:

implementation

type
  TWebCameraOpen = class(TWebCamera);

{$R *.dfm}

procedure TForm1.WebButton1Click(Sender: TObject);
begin
  WebCamera1.Start;
end;

procedure TForm1.HandleFlash(AActiveFlash: Boolean);
var
  torch, constraints: TJSObject;
begin
  torch := TJSObject.new;
  torch['torch'] := AActiveFlash;

  constraints := TJSObject.new;
  constraints['advanced'] := TJSArray.new(torch);

  TWebCameraOpen(WebCamera1).GetVideoTrack.applyConstraints(constraints);
end;

procedure TForm1.offBtnClick(Sender: TObject);
begin
  //Not guaranteed to work
  HandleFlash(False);
end;

procedure TForm1.onBtnClick(Sender: TObject);
begin
  HandleFlash(True);
end;

[Mika_Koistinen]

Thanks, this worked at least on my Oneplus Nord2 and huawei Mate 10 pro phones.