Zbar is not scanning small barcodes on ipod touch.why? - iphone

Question

I am having trouble reading small QR codes with ZBar using ipod. It seems I cannot get it to scan in 7mm x 7mm codes. Is this a configuration issue or a limitation of the ZBar library? I can scan these codes with other apps like pic2shop.
So,please tell me where i am mistaking.
Thank you.
ZBarReaderViewController *reader = [ZBarReaderViewController new];
reader.readerDelegate = self;
[reader.scanner setSymbology: ZBAR_I25
config: ZBAR_CFG_ENABLE
to: 0];
reader.showsZBarControls=NO;
reader.cameraOverlayView.frame=CGRectMake(0, 0, 320, 460);
reader.readerView.allowsPinchZoom = YES;
//reader.readerView.alpha=1.0;
reader.readerView.backgroundColor=[UIColor clearColor];
reader.wantsFullScreenLayout = YES;
reader.readerView.zoom=1.0;
[reader.readerView setScanCrop:(CGRect){ { 0.125, 0 }, { 0.75, 1} }];
[self.view addSubview:reader.view];
ZBarCaptureReader *cap=[[ZBarCaptureReader alloc]init];
cap.scanCrop=CGRectMake(10, 20, 100, 460);
[self presentModalViewController: reader animated: YES];
[reader release];

Answer 1

2 years later = There are issues with the resulting image size that Z Bar can work with. In particular as per documentation you need a minimum of 3 pixels per module (black or white stripe) so the image size needs to be bigger to scan properly. I had this issue in my iPad 2 which can read the barcode using the front camera but cannot read it with the rear camera (which produces grainy photos as well , this is contrary to the published camera specs for the iPad 2 which list the rear camera as the better of the 2 - I believe the specs were switched at some point in time). With Large QR Codes I need an iPhone 4S or iPhone 5 to scan properly and the videoQuality need to be set to high from the default VGA.
To remedy the problem above:
I would first try to remove the setScancrop line and initially start with the default (full screen) and capture as much of the barcode as possible. In particular CGRect values refer to origin (x,y) and size(width,length). I understand specifying {0,0}, {1.1} defaults to the full screen ((0,0),(320,480)) for iPhone 4GS, 4. 4s and old iTouch gen 3-4.
The next thing I will try is to use the ZBarReaderView class which takes manual still shots with higher resolution than the other class which gets the images from the video feed. the relevant parameters in this case is maxscansize, zoom, max zoom which are active in this mode but not in the other class.