mirror of
https://github.com/ruby-opencv/ruby-opencv
synced 2023-03-27 23:22:12 -04:00
64 lines
2.9 KiB
Ruby
Executable file
64 lines
2.9 KiB
Ruby
Executable file
#!/usr/bin/env ruby
|
|
#
|
|
# Detects contours in an image and
|
|
# their boundingboxes
|
|
#
|
|
require "opencv"
|
|
|
|
# Load image
|
|
cvmat = OpenCV::CvMat.load("rotated-boxes.jpg")
|
|
|
|
# The "canny" edge-detector does only work with grayscale images
|
|
# so to be sure, convert the image
|
|
# otherwise you will get something like:
|
|
# terminate called after throwing an instance of 'cv::Exception'
|
|
# 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
|
|
cvmat = cvmat.BGR2GRAY
|
|
|
|
# Use the "canny" edge detection algorithm (http://en.wikipedia.org/wiki/Canny_edge_detector)
|
|
# Parameters are two colors that are then used to determine possible corners
|
|
canny = cvmat.canny(50, 150)
|
|
|
|
# Look for contours
|
|
# We want them to be returned as a flat list (CV_RETR_LIST) and simplified (CV_CHAIN_APPROX_SIMPLE)
|
|
# Both are the defaults but included here for clarity
|
|
contour = canny.find_contours(:mode => OpenCV::CV_RETR_LIST, :method => OpenCV::CV_CHAIN_APPROX_SIMPLE)
|
|
|
|
# The Canny Algorithm returns two matches for every contour (see O'Reilly: Learning OpenCV Page 235)
|
|
# We need only the external edges so we ignore holes.
|
|
# When there are no more contours, contours.h_next will return nil
|
|
while contour
|
|
# No "holes" please (aka. internal contours)
|
|
unless contour.hole?
|
|
|
|
puts '-' * 80
|
|
puts "BOUNDING RECT FOUND"
|
|
puts '-' * 80
|
|
|
|
# You can detect the "bounding rectangle" which is always oriented horizontally and vertically
|
|
box = contour.bounding_rect
|
|
puts "found external contour with bounding rectangle from #{box.top_left.x},#{box.top_left.y} to #{box.bottom_right.x},#{box.bottom_right.y}"
|
|
|
|
# The contour area can be computed:
|
|
puts "that contour encloses an area of #{contour.contour_area} square pixels"
|
|
|
|
# .. as can be the length of the contour
|
|
puts "that contour is #{contour.arc_length} pixels long "
|
|
|
|
# Draw that bounding rectangle
|
|
cvmat.rectangle! box.top_left, box.bottom_right, :color => OpenCV::CvColor::Black
|
|
|
|
# You can also detect the "minimal rectangle" which has an angle, width, height and center coordinates
|
|
# and is not neccessarily horizonally or vertically aligned.
|
|
# The corner of the rectangle with the lowest y and x position is the anchor (see image here: http://bit.ly/lT1XvB)
|
|
# The zero angle position is always straight up.
|
|
# Positive angle values are clockwise and negative values counter clockwise (so -60 means 60 degree counter clockwise)
|
|
box = contour.min_area_rect
|
|
puts "found minimal rectangle with its center at (#{box.center.x.round},#{box.center.y.round}), width of #{box.size.width.round}px, height of #{box.size.height.round} and an angle of #{box.angle.round} degree"
|
|
end
|
|
contour = contour.h_next
|
|
end
|
|
|
|
# And save the image
|
|
puts "\nSaving image with bounding rectangles"
|
|
cvmat.save_image("rotated-boxes-with-detected-bounding-rectangles.jpg")
|