QRCODE recognition with zbar and PIL

gistfile1.py

def _decodeImage(self, imagePath):
		"""
		Get the QR code out of a given image file. This includes multiple
		attempts at scanning and a helpless attempt to increase image quality.
		"""
		# obtain image data
		pil = Image.open(imagePath).convert('L')
		width, height = pil.size
		# Resize to something reasonable, 512 px height
		aspectRatio = float(width) / height
		pil = pil.resize([int(aspectRatio * 512), 512])
		width, height = pil.size
		
		logging.debug("QR image opened, " + imagePath + ": " + repr(width) + "x" + repr(height))
		
		resultTimecode = False
		enhanceAttempt = 0
		
		while enhanceAttempt < 10 and not resultTimecode:
			try:
				resultTimecode = self._scanForQrCode(pil)
			except errors.NoQrTimecodeDetectedError:
				# Fail? Make the image better!
				# Enhance contrast
				contrastEnhancer = ImageEnhance.Contrast(pil)
				pil = contrastEnhancer.enhance(2.5)
				# Blur some
				pil = pil.filter(ImageFilter.BLUR)
				enhanceAttempt += 1
		#pil.show()
		if not resultTimecode:
			raise errors.NoQrTimecodeDetectedError("Gave up finding QR, enhancing didn't help")
		
		return resultTimecode
		
	def _scanForQrCode(self, pil):
		"""
		Scan for a QR code in a given PIL image
		"""
		width, height = pil.size
		raw = pil.tostring()
		# create a reader
		scanner = zbar.ImageScanner()
		# configure the reader
		scanner.parse_config('enable')
		# wrap image data
		image = zbar.Image(width, height, 'Y800', raw)
		# scan the image for barcodes
		scanner.scan(image)
		# extract results
		resultTimecode = False
		
		for symbol in image:
			# look for a QRCODE result
			logging.debug("zbar found a symbol, " + repr(symbol.type) + ": " + symbol.data)
			if symbol.type == 64: # 64 -> QRCODE
				resultTimecode = symbol.data
		# Nothing found?
		if not resultTimecode:
			raise errors.NoQrTimecodeDetectedError("No QR code found")
		# clean up
		del(image)
		
		return float(resultTimecode)