How to recognize vehicle license number plate ANPR from an image

Question

I have a web site that allows users to upload images of cars and I would like to put a privacy filter in place to detect registration plates on the vehicle and blur them   The blurring is not a problem but is there a library or component  open source preferred  that will help with finding a licence within a photo   Caveats    I know nothing is perfect and image recognition of this type will provide false positive and negatives  I appreciate that we could ask the user to select the area to blur and we will do this as well  but the question is specifically about finding that data programmatically  so answers such as  get a person to check every image  is not helpful  This software method is called  Automatic Number Plate Recognition  in the UK but I cannot see any implementations of it as libraries  Any language is great although  Net is preferred

User · Answer

Yes I use gocr at http   jocr sourceforge net  its a commandline application which you could execute from your application  I use it in a couple of my applications

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It maybe work looking at Character recoqnition software as there are many libraries out there that perform the same thing  I reading an image and storing it  Micrsoft office is able to read tiff files and return alphanumerics

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I coded a C  version based on JAVA ANPR  but I changed the awt library functions with OpenCV  You can check it at http   anprmx codeplex com

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I came across this one that is written in java javaANPR  I am looking for a c  library as well   I would like a system where I can point a video camera at some sailing boats  all of which have large  identifiable numbers on them  and have it identify the boats and send a tweet when they sail past a video camera

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I have done some googling about this a couple of months ago  There are quite a few papers about this topic  but I never found any concrete open-source implementation  There are a lot of commercial implementations though  but none of them with a price quote  so they re probably pretty expensive

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High performance ANPR Library - http   www dtksoft com dtkanpr php  This is commercial  but they provide trial key

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Have a look at Java ANPR  Free license plate recognition

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The blurring is not a problem but is there a library or component  open source preferred  that will help with finding a licence within a photo   Ans  The CARMEN FreeFlow ANPR Software engine  Commerical

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EDIT  I wrote a Python script for this   As your objective is blurring  for privacy protection   you basically need a high recall detector as a first step  Here s how to go about doing this  The included code hints use OpenCV with Python       Convert to Grayscale  Apply Gaussian Blur   img   cv2 imread  input jpg  1  img gray   cv2 cvtColor img  cv2 COLOR BGR2GRAY  img gray   cv2 GaussianBlur img gray   5 5   0       Let  the input image be the following          Apply Sobel Filter to detect vertical edges  Threshold the resultant image using strict threshold or OTSU s binarization     cv2 Sobel image  -1  1  0  cv2 threshold     Apply a Morphological Closing operation using suitable structuring element   I used 16x4 as structuring element   se   cv2 getStructuringElement cv2 MORPH RECT  16 4   cv2 morphologyEx image  cv2 MORPH CLOSE  se       Resultant Image after Step 5          Find external contours of this image    cv2 findContours image  cv2 RETR EXTERNAL  cv2 CHAIN APPROX NONE    For each contour  find the minAreaRect   bounding it  Select rectangles based on aspect ratio  minimum and maximum area  and angle with the horizontal   I used 2 2  lt   Aspect Ratio  lt   8  500  lt   Area  lt  15000  and angle  lt   45 degrees    All minAreaRect  s are shown in orange and the one which satisfies our criteria is in green          There may be false positives after this step  to filter it  use edge density  Edge Density is defined as the number of white pixels total number of pixels in a rectangle  Set a threshold for edge density   I used 0 5         Blur the detected regions        You can apply other filters you deem suitable to increase recall and precision  The detection can also be trained using HOG SVM to increase precision

User · Answer

There is a new  open source library on GitHub that does ANPR for US and European plates   It looks pretty accurate and it should do exactly what you need  recognize the plate regions    Here is the GitHub project  https   github com openalpr openalpr

User · Answer

http   licenseplate sourceforge net Python  I have not tested it

User · Answer

try this Simple Automatic Number Plate Recognition System  http   opos codeplex com   Open source and written with C

[image] How to recognize vehicle license / number plate (ANPR) from an image?

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