Date post: | 08-Jul-2015 |
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WELCOME
A low pre-processing system for
restoring low quality QR code
images
Presenting by-
Shameed C M
Roll No:49
S7 CS
Reg No:12123852
College of Engineering Attingal
Contents
Introduction
What is a QR code ?
History of QR code
Bar code VS QR code
Inside QR codes
What can a QR code do?
Application of QR code
Pre-processing
QR code decoding
Conclusion
References
Introduction
2D barcodes are the mainstream of recognition technologies used
for mobile marketing.
Easily conversion of physical printed data to digital data
2D barcodes are called two-dimensional because their information
is encoded in two directions, both horizontally and vertically.
WHAT IS A QR CODE ?
QR code: Quick Response code
Is a 2-D bar code
Used to encode information(URLs, automated SmS, text data) in two dimensional space.
HISTORY
Created by a Japanese
company- Toyota subsidiary
Denso-wave in 1994.
Used to track parts during vehicle
manufacture
Barcodes V/S QR Codes
Stores data in two dimensions unlike the 1-D barcodes.
High storage capacity in less space.
Can be scanned by any smart phone with the app installed.
Inside QR codes
Finder Patterns: Finds if the given code is a QR Code
Timing Pattern: Tracks the timing of the incoming code
Separators: Separates data from the patterns
Alignment Pattern: Tells about initiation & Separation of data.
Dark Module: A black module placed beside the bottom left finder pattern.
Cont…
Many Alignment patterns
Long timing pattern
Versions of QR code
Version 1 (21×21)
Version 2 (25×25)
Version 3 (29×29)
Versions of QR code cont…
Version 4 (33×33)
Version 10 (57×57)
Version 25 (117×117 enlarged to
640x640)
Versions of QR code cont…
Version 40 (177×177)
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Take a snap and view web page
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Capture and call
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Take a snap and send a template
message
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
snap and send a default mail
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Take a snap
and see the
message
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Capture and save contact
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Capture and recognize the exact place
What can a QR code do?
View a web page
Dial telephone number
Send a template text message
Send an e-mail
View a message or special offer
Download contact details (vcard)
View a google maps location
View a social media profile
Snap and see the media profile
Applications
Conference/event displays
Print advertisements
Business cards
Brochures , posters, & flyers
Post cards & mail
Applications
Conference/event displays
Print advertisements
Business cards
Brochures , posters, & flyers
Post cards & mail
Applications
Conference/event displays
Print advertisements
Business cards
Brochures , posters, & flyers
Post cards & mail
Applications
Conference/event displays
Print advertisements
Business cards
Brochures , posters, & flyers
Post cards & mail
Applications
Conference/event displays
Print advertisements
Business cards
Brochures , posters, & flyers
Post cards & mail
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the code
Code alignment : corner and pattern detection and
transformation
Scanning the code
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the QR code
Pattern detection
Scanning the code
The images are captured by a 3 Megapixel-sensor
continuously refreshed on the screen to provide the user
with some feedback during the image capture process
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the QR code
Pattern detection
Scanning the code
To balance environment light effect
Histogram equalization
It is a method in image processing of contrast adjustment
using the image's histogram.
Employs a monotonic, non-linear mapping which re-assigns
the intensity values of pixels in the input image such that the
output image contains a uniform distribution of intensities
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the QR code
Pattern detection
Scanning the code
Cropping out external surroundings
Image binarisation
Edge detection
Morphological operations
Quality index
QR code extraction
1. Image binarisation
Binarization image by multi-level
thresholding method.
Captured imageThe simplest way to use image binarisation is to
choose a threshold value, and classify all pixels
with values above this threshold as white, and all
other pixels as black.
There are only two levels of intensity in the binary
image. We consider the pixels that have low
intensity is an image pixel where high intensity as
background pixel.
QR code extraction cont…
2. Edge detection
I. Smoothing
II. Finding gradients
III. Non maximum suppression
IV. Double thresholding
V. Edge tracking by hysteresis
QR code extraction cont…
2. Edge detection
I. SmoothingII. Finding gradients
III. Non maximum suppression
IV. Double thresholding
V. Edge tracking by hysteresis
Blurring the image to avoid noise.
QR code extraction cont…
2. Edge detection
I. Smoothing
II. Finding gradientsIII. Non maximum suppression
IV. Double thresholding
V. Edge tracking by hysteresis
The edges should be marked where the gradients
of the image has large magnitudes.
The algorithm basically finds edges where the
greyscale intensity of the image changes the most.
These areas are found by determining gradients of
the image.
QR code extraction cont…
2. Edge detection
I. Smoothing
II. Finding gradients
III. Non maximum suppressionIV. Double thresholding
V. Edge tracking by hysteresis
Only local maxima should be marked as edges.
The purpose of this step is to convert the “blurred”
edges in the image of the gradient magnitudes to
“sharp” edges.
Basically this is done by preserving all local
maxima in the gradient image and deleting
everything else.
QR code extraction cont…
2. Edge detection
I. Smoothing
II. Finding gradients
III. Non maximum suppression
IV. Double thresholdingV. Edge tracking by hysteresis
The edge-pixels remaining after the non-
maximum suppression step are marked with their
strength pixel-by-pixel.
The edge detection algorithm uses double
thresholding.
QR code extraction cont…
2. Edge detection
I. Smoothing
II. Finding gradients
III. Non maximum suppression
IV. Double thresholding
V. Edge tracking by hysteresis
Final edges are determined by suppressing all
edges that are not connected to a true (strong)
edge.
Thus strong edges will (almost) only be due to true
edges in the original image.
The weak edges can either be due to true edges
or noise/color variations.
QR code extraction cont…
3. Morphological operations
I. Morphological dilation
II. Morphological closing
Morphological operations are affecting the form, structure or shape of
an object.
used for getting a representation or description of the shape of
objects/regions.
QR code extraction cont…
3. Morphological operations
I. Morphological dilation
II. Morphological closingDilation adds pixels to the boundaries of objects
in an image.
The number of pixels added to the objects in an
image depends on the size and shape of the
structuring element used to process the image.
QR code extraction cont…
3. Morphological operations
I. Morphological dilation
II. Morphological closing Closing removes small holes(islands) and other
thin filaments of background pixels.
i.e.; it can fill holes in the regions while keeping
the initial region sizes.
QR code extraction cont…
4. Quality index
I. Error correction
II. Discard low quality images
Used in further modules as a parameter to check the quality.
QI has been designed so that it can be readily computed for every
input image once the QR code area has been extracted.
QR code extraction cont…
4. Quality index
I. Error correction
II. Discard low quality images
For error correction the Reed-Solomon code is
used.
It is a non binary cyclic-error correcting code.
It is has some steps
Takes block of data.
Adds “redundant” bits to form a code
word.
The code word can be decoded to
correct for lost or corrupted bits.
QR code extraction cont…
4. Quality index
I. Error correction
II. Discard low quality images The very low quality images are more complex
in the deblurring module, so the image will be
avoided
QR code extraction cont…
Contrast adjustment and code extraction: (a) captured image; (b) contrast- enhanced image;
(c) Binarized image; (d) external elements removal;(e) edge detection; (f) high edge density area
identification after dilation; (g) high edge density area identification after dilation and closing;
and (h) codeextraction
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the QR code
Pattern detection
Scanning the code
Although ideally QR codes are two-tone images.
Used some deblurring algorithms.
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the QR code
Pattern detection
Scanning the code
determine the proper compensating transform, the four
corners of the code have to be determined and the patterns
of the QR code detected.
The corner coordinates associated with the three finder
patterns are considered precise enough.
the fourth corner must be refined since it may be actually
defined by position of the finder patterns, which is
undetectable by the scanning, causing pixel loses.
Pre-processing
Capturing image
Contrast enhancement
QR code extraction
Deblurring the QR code
Pattern detection
Scanning the code
Decoding the printed data to the digital data
Decoding QR code
The QR code to decoding
Decoding QR code cont…
Grouping to octets…
Decoding QR code cont…
Decoding QR code cont…
Decoding QR code cont…
Conclusion
In this paper, a practical image Pre-processing method was
proposed for QR code recognition.
The influence by background noise and inhomogeneous light and
geometric distortion was minimized.
In additional, it used alignment patterns to adaptively sample the
barcode in terms of regions, which greatly improved the recognition
rate.
The number of calculation of this algorithm is reduced, its
recognition speed is higher.
References
[1]IEEE Explore ,Munoz-mejias,Gonzalez-Diaz,Diaz-de-Maria:” A low
pre-processing system for restoring low quality QR code images”
[2]Wikipedia/QR-code
[3]Yunhua Gu,Weixiang Zhang,"QR code recognition Based on
Image Processing",International Conference on Information Science
and Technology ,March 26-28, 2011 Nanjing, Jiangsu, China
[4]M.Sun,LS.Fu,XTYang,S.H.zhang,"Image Analysis Method for QR
Code's Automatic Recognition",Journal of University of Electronic
Science and Technology of China, Vo1.38,No.6,pp.122-
125,Nov.2009.
QUERIES