I dont understand how appending the contour is supposed to add this method.
Learn more. How do I validate OpenCV gives me contours? Ask Question. Asked 3 years, 4 months ago.
Active 3 years, 4 months ago. Viewed 2k times. Full source from imutils. Hence the error. I see the error, thank you. Should I delete this?
Bubble sheet multiple choice scanner and test grader using OMR, Python and OpenCV – PyImageSearch
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Sign up. Bubble sheet multiple choice scanner example with OpenCV. Java Branch: master. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. This branch is 5 commits behind m-cakir:master. Pull request Compare.
Latest commit Fetching latest commit…. Install Download OpenCV from offical site. Output for sheet You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window.One of my favorite parts of running the PyImageSearch blog is demonstrating how to build actual solutions to problems using computer vision.
In fact, what makes this project so special is that we are going to combine the techniques from many previous blog posts, including building a document scannercontour sortingand perspective transforms. You see, last Friday afternoon I quickly Photoshopped an example bubble test paper, printed out a few copies, and then set to work on coding up the actual implementation. To learn more about utilizing computer vision, image processing, and OpenCV to automatically grade bubble test sheets, keep reading.
Optical Mark Recognition, or OMR for short, is the process of automatically analyzing human-marked documents and interpreting their results. Arguably, the most famous, easily recognizable form of OMR are bubble sheet multiple choice testsnot unlike the ones you took in elementary school, middle school, or even high school.
The most notable bubble sheet test you experienced at least in the United States were taking the SATs during high school, prior to filling out college admission applications. Below I have included an example filled in bubble sheet exam that I have put together for this project:.
Figure 1: The example, filled in bubble sheet we are going to use when developing our test scanner software. I have also included a blank exam template as a.
PSD Photoshop file so you can modify it as you see fit. The goal of this blog post is to build a bubble sheet scanner and test grader using Python and OpenCV. The next section of this tutorial will cover the actual implementation of our algorithm. Now that we have the outline of our exam, we apply the cv2. We do this by sorting our contours by their area from largest to smallest on Line 37 after making sure at least one contour was found on Line 34of course. This implies that larger contours will be placed at the front of the list, while smaller contours will appear farther back in the list.
We make the assumption that our exam will be the main focal point of the imageand thus be larger than other objects in the image. However, contour area and size is not enough — we should also check the number of vertices on the contour.
To do, this, we loop over each of our sorted contours on Line You can read more about contour approximation in this post on building a mobile document scanner. On Line 47 we make a check to see if our approximated contour has four points, and if it does, we assume that we have found the exam. Below I have included an example image that demonstrates the docCnt variable being drawn on the original image:.
Figure 3: An example of drawing the contour associated with the exam on our original image, indicating that we have successfully found the exam. Now that we have used contours to find the outline of the exam, we can apply a perspective transform to obtain a top-down, birds-eye-view of the document:. Figure 4: Obtaining a top-down, birds-eye view of both the original image left along with the grayscale version right. Notice how the background of the image is blackwhile the foreground is white.
Tutorial: Creating a Multiple Choice Scanner with OpenCV
This binarization will allow us to once again apply contour extraction techniques to find each of the bubbles in the exam:. To determine which regions of the image are bubbles, we first loop over each of the individual contours Line For each of these contours, we compute the bounding box Line 73which also allows us to compute the aspect ratioor more simply, the ratio of the width to the height Line As long as these checks hold, we can update our questionCnts list and mark the region as a bubble.
Below I have included a screenshot that has drawn the output of questionCnts on our image:. Figure 6: Using contour filtering allows us to find all the question bubbles in our bubble sheet exam recognition software. First, we must sort our questionCnts from top-to-bottom. This will ensure that rows of questions that are closer to the top of the exam will appear first in the sorted list.
We also initialize a bookkeeper variable to keep track of the number of correct answers. On Line 90 we start looping over our questions.
The reason this methodology works is because we have already sorted our contours from top-to-bottom. We know that the 5 bubbles for each question will appear sequentially in our list — but we do not know whether these bubbles will be sorted from left-to-right.
The sort contour call on Line 94 takes care of this issue and ensures each row of contours are sorted into rows, from left-to-right.Calibre has the ability to view, convert, edit, and catalog e-books of almost any e-book format. Attendize is a free and open source ticket selling and event management platform designed to give event organizers a simple, affordable yet full-featured solution for managing general admission events.
Power users can automate WinSCP using. NET assembly. WinSCP is available in English and many other languages. Its simple user interface lets you manage scanner and printer options with a few clicks.
Its features include regular expressions, versatile printing options, stores most recent used paths and has a "context" feature which is very nice for looking at source code. Get the latest uniCenta oPOS v4. It is multi-location, multi-terminal and multi-user and runs on industry standard Do you have a GitHub project? Now you can sync your releases automatically with SourceForge and take advantage of both platforms. ConEmu-Maximus5 aims to be handy, comprehensive, fast and reliable terminal window where you may host any console application developed either for WinAPI cmd, powershell, far or Unix PTY cygwin, msys, wsl bash.
As Windows console window enhancement local terminal emulatorit presents multiple consoles and simple GUI applications as one customizable tabbed GUI window with various features. Also, due to deep integration, ConEmu is the best companion for Far Manager, my favorite shell FastPhotoTagger tries to be the fastest way to set the metadata in your photos.
Add, change, delete, and search the metadata fields of your choice. FastPhotoTagger excels when you have lots of files and lots of metadata. With FastPhotoTagger, you can - Set multiple images to have the same tag values - Set individual images to have unique tag values - Display all the metadata in an image - Compare and edit all the metadata in several images - Choose the metadata fields to work with: EXIF, XMP Pydio Cells is the mature open source alternative to dropbox and box, for the enterprise.
Why building your own box? You need to access your documents across multiple devices, and regularly share documents weblinks and folders with your contacts and teams. Still, using a consumer SaaS box or drive service is neither practical nor safe. And enterprise SaaS box or drive services are expensive and come with Disk Storage that you already have on your servers or private cloud.
Learn more. Bubble sheet multiple choice scan Ask Question. Asked 2 years, 11 months ago. Active 2 years, 11 months ago.
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Viewed times. Mohammad Sadiqur Rahman 3, 6 6 gold badges 25 25 silver badges 38 38 bronze badges. Hoang Ngoc Hoang Ngoc 1 1 1 bronze badge. Can you please state what exactly you want to do? Apr 21 '17 at Active Oldest Votes. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. The Overflow How many jobs can be done at home? Featured on Meta. Community and Moderator guidelines for escalating issues via new response….
Hi Michael. Very nice post. Is the code available too? Hello, I can show your post in my Blog. It's work and code complete. Very nice post! Hi Michael…Could you send me the code, plzz? Hi Michael…Could you send me the code? Hi Michael, Could you send me the code and image?
I am struggling the all day to get the same result but somethings go wrong always, I am working on Mac and opencv version 2. Hi Michael, Can you send me your code please? Hi Michael, Can have the code too? Could you send me the code? Hi, Great code. Could you send mo the code. I"ll appreciate it a lot. Hi Michael, your tutorial is very helpful.
There is one problem. I found more than one line for my edges, totaly I changed the parameters of functions but i could not overcome. I think that merging or averaging lines is reasonable but I couldn't find the way. Do you have any suggestion?
Hi Michael, thanks for sharing your knowledge. Can you send me a code. Hi Michael, This is superb.About Us. Video Tutorials. Formscanner is a free, open-source OMR optical mark recognition software for scanning and grading user-filled, multiple choice forms.
Formscanner is easy to use, effective, and completely free of cost and advertisements. Users scan the forms and, in just a couple of steps, they have a spreadsheet with students' scores, answers to individual questions, and detailed analysis of the class' perfomance. Other OMR software costs hundreds, but FormScanner is open-source, community-supported, easy-to-use, and excellent at what it does. Version 1. Update your FormScanner today! Get the latest version of Process Bubbles on the downloads page.
It can now deduct points for incorrect answers and apply partial credit when a student gets some o f the multiple responses correct. It can also support multiple versions of exams.OMR Evaluator
Also, we just had a paper accepted to The Physics Teacher. Look for it in an upcoming issue. Like FormScanner? Consider donating. Formscanner Formscanner is a free, open-source OMR optical mark recognition software for scanning and grading user-filled, multiple choice forms. Latest News and Updates Version 1. Michela Battauz just released a statistical package, fsia, for use with FormScanner.
Find it on the r-project site:.