mirror of
https://github.com/ruby-opencv/ruby-opencv
synced 2023-03-27 23:22:12 -04:00
45 lines
1.8 KiB
Ruby
45 lines
1.8 KiB
Ruby
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#!/usr/bin/env ruby
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#
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# Detects contours in an image and
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# their boundingboxes
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#
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require "opencv"
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# Load image
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cvmat = OpenCV::CvMat.load("rotated-boxes.jpg")
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# The "canny" edge-detector does only work with grayscale images
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# so to be sure, convert the image
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# otherwise you will get something like:
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# terminate called after throwing an instance of 'cv::Exception'
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# what(): /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_graphics_opencv/work/OpenCV-2.2.0/modules/imgproc/src/canny.cpp:67: error: (-210) in function cvCanny
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cvmat = cvmat.BGR2GRAY
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# Use the "canny" edge detection algorithm (http://en.wikipedia.org/wiki/Canny_edge_detector)
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# Parameters are two colors that are then used to determine possible corners
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canny = cvmat.canny(50, 150)
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# Look for contours
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# We want them to be returned as a flat list (CV_RETR_LIST) and simplified (CV_CHAIN_APPROX_SIMPLE)
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# Both are the defaults but included here for clarity
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contour = canny.find_contours(:mode => OpenCV::CV_RETR_LIST, :method => OpenCV::CV_CHAIN_APPROX_SIMPLE)
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# The Canny Algorithm returns two matches for every contour (see O'Reilly: Learning OpenCV Page 235)
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# We need only the external edges so we ignore holes.
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# When there are no more contours, contours.h_next will return nil
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while contour
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# No "holes" please (aka. internal contours)
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unless contour.hole?
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box = contour.bounding_rect
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puts "found external contour from #{box.top_left.x},#{box.top_left.y} to #{box.bottom_right.x},#{box.bottom_right.y}"
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# Draw that bounding rectangle
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cvmat.rectangle! box.top_left, box.bottom_right, :color => OpenCV::CvColor::Black
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end
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contour = contour.h_next
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end
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# And save the image
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puts "Saving image with bounding rectangles"
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cvmat.save_image("rotated-boxes-with-detected-bounding-rectangles.jpg")
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