title: Open zbar scanner in certain part of Screen
body: <p>I have a app in which i have implemented Qr code scanning using ZBar.</p>
  
  <p>Now i have also implemented overlay on camera.</p>
  
  <p>The problem is though i have make a overlay, the camera scan whole part of screen.</p>
  
  <p>I want to scan on certain part of screen.</p>
  
  <p>Here is my code,</p>
  
  <pre><code>    reader = [ZBarReaderViewController new];
      isCameraStarted = YES;
  
      reader.readerDelegate = self;
      reader.supportedOrientationsMask = ZBarOrientationMaskAll;
  
      //Add flash Camera
      if(isTorchOn==NO)
          reader.cameraFlashMode=UIImagePickerControllerCameraFlashModeOff;
      else
          reader.cameraFlashMode=UIImagePickerControllerCameraFlashModeOn;
  
      ZBarImageScanner *scanner = reader.scanner;
      // TODO: (optional) additional reader configuration here
  
      // EXAMPLE: disable rarely used I2/5 to improve performance
      [scanner setSymbology: ZBAR_I25
                     config: ZBAR_CFG_ENABLE
                         to: 0];
  
      [scanner setSymbology:ZBAR_NONE config:ZBAR_CFG_ENABLE to:0];
      [scanner setSymbology:ZBAR_QRCODE
                     config:ZBAR_CFG_ENABLE
                         to:1];
      reader.cameraOverlayView = vw;
          reader.showsZBarControls=NO;
      [self presentViewController:reader animated:NO completion:nil];
      [reader release];
  </code></pre>
  
  <p>open the camera in square middle box</p>
  
  <p>Here is the out put i want:</p>
  
  <p><img src="https://i.stack.imgur.com/WBbbn.png" alt=""></p>