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Example for contour retrieval modes
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Frank Schumacher
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3 changed files with 139 additions and 0 deletions
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139
examples/contours/contour_retrieval_modes.rb
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139
examples/contours/contour_retrieval_modes.rb
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#!/usr/bin/env ruby
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#
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# This file shows the different retrieval modes for contour detection
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#
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require "opencv"
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# Load image
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# The structure of the image is "explained" in bitmap-contours-with-labels.png
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cvmat = OpenCV::CvMat.load("bitmap-contours.png")
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# "find_contours" does only operate on bitmap images (black/white)
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mat = OpenCV::CvMat.new(cvmat.rows, cvmat.cols, :cv8u, 1)
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(cvmat.rows * cvmat.cols).times do |i|
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mat[i] = (cvmat[i][0] <= 128) ? OpenCV::CvScalar.new(0) : OpenCV::CvScalar.new(255)
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end
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# find_contours takes two parameters:
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# 1. Retrieval mode (:mode, defines the structure of the contour sequence returned)
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# - CV_RETR_LIST (default)
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# - CV_RETR_EXTERNAL
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# - CV_RETR_CCOMP
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# - CV_RETR_TREE
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# 2. Retrieval Method (:method, how the contours are approximated)
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# - CV_CHAIN_CODE
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# - CV_CHAIN_APPROX_NONE
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# - CV_CHAIN_APPROX_SIMPLE (default)
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# - CV_CHAIN_APPROX_TC89_L1
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# - CV_CHAIN_APPROX_T89_KCOS
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# - CV_LINK_RUNS
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#
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# The default: CV_RETR_LIST and CV_CHAIN_APPROX_SIMPLE
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# This produces a flat list of contours that can be traversed with .h_next and .h_prev
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#
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puts "Detecting using CV_RETR_LIST and CV_CHAIN_APPROX_SIMPLE"
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contour = mat.find_contours(:mode => OpenCV::CV_RETR_LIST, :method => OpenCV::CV_CHAIN_APPROX_SIMPLE)
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cindex=1
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while contour
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puts "Contour ##{cindex} is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.h_next
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cindex+=1
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end
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#
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# CV_RETR_EXTERNAL retrieves only the outer most non "hole" contour
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#
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puts '-'*80
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puts "Detecting using CV_RETR_EXTERNAL and CV_CHAIN_APPROX_SIMPLE"
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contour = mat.find_contours(:mode => OpenCV::CV_RETR_EXTERNAL, :method => OpenCV::CV_CHAIN_APPROX_SIMPLE)
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cindex=1
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while contour
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puts "Contour ##{cindex} is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.h_next
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cindex+=1
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end
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#
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# CV_RETR_CCOMP organizes the contours in a two level deep stack
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# The first level holds the contours
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# The second level contains the holes of the contours in level 1
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#
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# C00001 <-> C00000 <-> C000 <-> C0
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# | |
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# V V
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# H0000 H00
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#
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puts '-'*80
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puts "Detecting using CV_RETR_CCOMP and CV_CHAIN_APPROX_SIMPLE"
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contour = mat.find_contours(:mode => OpenCV::CV_RETR_CCOMP, :method => OpenCV::CV_CHAIN_APPROX_SIMPLE)
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# C00001
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puts "Contour #1 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.h_next
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# C00000
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puts "Contour #2 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.h_next
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# C000
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puts "Contour #3 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour_down = contour.v_next
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# H0000
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puts "Contour #4 is #{contour_down.contour_area} px^2 (width: #{contour_down.bounding_rect.width}, height: #{contour_down.bounding_rect.height}, type: #{(contour_down.hole?)?"hole":"contour"})"
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contour = contour.h_next
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# C0
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puts "Contour #5 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour_down = contour.v_next
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# H00
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puts "Contour #6 is #{contour_down.contour_area} px^2 (width: #{contour_down.bounding_rect.width}, height: #{contour_down.bounding_rect.height}, type: #{(contour_down.hole?)?"hole":"contour"})"
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#
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# CV_RETR_TREE manages the contours in a tree structure
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# This reconstructs the complete hierarchy of contours and holes that the image displayed
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#
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# C0
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# |
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# V
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# H00
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# |
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# V
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# C000
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# |
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# V
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# H0000-------+
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# | |
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# V V
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# C00000 C00001
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#
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puts '-'*80
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puts "Detecting using CV_RETR_TREE and CV_CHAIN_APPROX_SIMPLE"
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contour = mat.find_contours(:mode => OpenCV::CV_RETR_TREE, :method => OpenCV::CV_CHAIN_APPROX_SIMPLE)
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# C0
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puts "Contour #1 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.v_next
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# H00
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puts "Contour #2 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.v_next
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# C000
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puts "Contour #3 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.v_next
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# H0000
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puts "Contour #4 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour = contour.v_next
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# C00000
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puts "Contour #5 is #{contour.contour_area} px^2 (width: #{contour.bounding_rect.width}, height: #{contour.bounding_rect.height}, type: #{(contour.hole?)?"hole":"contour"})"
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contour_right = contour.h_next
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# C00001
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puts "Contour #6 is #{contour_right.contour_area} px^2 (width: #{contour_right.bounding_rect.width}, height: #{contour_right.bounding_rect.height}, type: #{(contour_right.hole?)?"hole":"contour"})"
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