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I am working on a project where I need to program a Raspberry Pi to grab an image from a webcam, search that image for a box and identify what box it is by it's size ratio. The boxes will be a unique color to the rest of the environment. It would also be good to identify the distance from the box and angle to the box.

Everything I've seen seems to indicate that this should be possible, but after several days of searching I have yet to find anything that really helps me to do this. This project is my first experience using Python, so I'm pretty newbish. Any help even with how to do little portions of this would be greatly appreciated.

Here's my working code so far. It's not much, all it does is grab an image from a webcam :/

import imgproc
from img imgproc *
camera = Camera(160, 120)
viewer = Viewer(160, 120)
n = 1
while (n > 0):
     img = camera.grabImage()
     viewer.displayImage(img)
YXD
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Bob Setlock
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2 Answers2

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This is not a complete solution, but some good ideas on how to get started :)

First off, there are Python bindings for OpenCV, an open source free computer vision library originally written in C: http://opencv.willowgarage.com/documentation/python/index.html

The first thing you have to do when solving a computer vision problem is pre-process. In particular, knowing that the box is a different colour helps a LOT - it means we can threshold by colour and create an image that is black where the box is not, and white where the box is, using a technique such as in http://aishack.in/tutorials/thresholding/ .

Then, you'd follow a process similar to the Sudoku grabber/solver described in this blog - you do blob extraction ( http://en.wikipedia.org/wiki/Blob_extraction ) then do a hough transform to get lines, and then you can compare the lines' distances to each other to determine the box's ratio. http://aishack.in/tutorials/sudoku-grabber-with-opencv-plot/

Pretty much just read about people's OpenCV Sudoku solvers until you get the gist of how it's done, because there are a lot of good tutorials and it's a simple illustration of how computer vision projects go: https://www.google.com.au/search?q=sudoku+opencv&aq=f&oq=sudoku+opencv&aqs=chrome.0.57j60l3j0l2.1506&sourceid=chrome&ie=UTF-8

Utkarsh Sinha
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Patashu
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You may want to try installing SimpleCV from the github repo. Using SimpleCV you should be able to get the blob's color using the Image.hueDistance command. If you use the findBlobs command to find your boxes each blob should have its aspect ratio as a parameter. We just posted our full PyCon tutorial about SimpleCV here. You can view just the slides here. We've heard that there are some issues installing PyGame (a SimpleCV dependency) on the RaspberryPi. This walk through might address those issues.

kscottz
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