ffi-facedetect.rb

# stripped cvHaarDetectObjects version of ffi-opencv
#  % pacman -S opencv  (tested/updated for 2.3.1)
#  % ruby ffi-facedetect.rb some.png

require 'ffi'

module OpenCv
  extend FFI::Library
  ffi_lib 'opencv_objdetect'

  attach_function :cvGetErrStatus, [], :int
  attach_function :cvLoadImage, [:string, :int], :pointer
  attach_function :cvSaveImage, [:string, :pointer], :int
  attach_function :cvLoad, [:string, :int, :int, :int], :pointer

  CV_MAGIC_MASK     = 0xFFFF0000
  CV_HAAR_MAGIC_VAL = 0x42500000
  CV_TYPE_NAME_HAAR = "opencv-haar-classifier"
  CV_HAAR_DO_CANNY_PRUNING = 1
  def self.is_haar_classifier(haar_ptr)
    if haar_ptr.respond_to?(:address) && haar_ptr.address != 0
      haar_ptr.get_int(0) & CV_MAGIC_MASK == CV_HAAR_MAGIC_VAL
    end
  end

  attach_function :cvCreateMemStorage, [:int], :pointer
  attach_function :cvClearMemStorage, [:pointer], :int
  attach_function :cvReleaseMemStorage, [:pointer], :int
  attach_function :cvHaarDetectObjects, [:pointer, :pointer, :pointer, :double, :int, :int, :int, :int], :pointer
  attach_function :cvGetSeqElem, [:pointer, :int], :pointer

  HaarTreeDefault = "/usr/share/opencv/haarcascades/haarcascade_frontalface_alt.xml"
end


filename = ARGV.last
exit 1 unless File.exists? filename


iplimage = OpenCv.cvLoadImage(filename, 1)
  if OpenCv.cvGetErrStatus != 0
    p 'ERROR loading file; no valid haar classifier'; exit 1
  end


cascade = OpenCv.cvLoad(OpenCv::HaarTreeDefault, 0, 0, 0)
  unless OpenCv.is_haar_classifier(cascade)
    p 'ERROR loading file; no valid haar classifier'; exit 1
  end


storage = OpenCv.cvCreateMemStorage(0); OpenCv.cvClearMemStorage(storage)
scale_haar = 1.2


faces = OpenCv.cvHaarDetectObjects(iplimage, cascade, storage, scale_haar, 2, OpenCv::CV_HAAR_DO_CANNY_PRUNING, 5, 5)
#OpenCv.cvGetErrStatus


x86_64 = FFI.type_size(:pointer) == 8

if (found_count = faces.get_uint( x86_64 ? 40 : 24 )) != 0
  rects = 0.upto(found_count-1).map do |idx|
    OpenCv.cvGetSeqElem(faces, idx).get_array_of_int(0, 4)
  end

  puts "found %i faces:\n%s" % [found_count, rects.inspect]
  rects
end