Contents

require 'narray'

module Mork
  # NPatch handles low-level computations on pixels
  # it is basically a wrapper around NArray
  class NPatch
    def initialize(source, width, height)
      @patch = NArray.byte(width, height)
      @patch[true] = case source
                     when Array
                       source
                     when String
                       IO.read("|convert #{source} gray:-").unpack 'C*'
                     else
                       raise 'Invalid NPatch init param'
                     end
      @width  = width
      @height = height
    end
    
    def average(c=nil)
      crop(c).mean
    end
    
    def length
      @patch.length
    end
    
    def dark_centroid(c = nil)
      p = crop c
      sufficient_contrast?(p) or return
      xp = p.sum(1).to_a
      yp = p.sum(0).to_a
      # find the intensity trough
      ctr_x = xp.find_index(xp.min)
      ctr_y = yp.find_index(yp.min)
      return ctr_x, ctr_y
    end
    
    private
    
    def crop(c)
      c =  {x: 0, y: 0, w: @width, h: @height} if c.nil?
      x = c[:x]...c[:x]+c[:w]
      y = c[:y]...c[:y]+c[:h]
      p = NArray.float c[:w], c[:h]
      p[true,true] = @patch[x, y]
      p
    end
    
    def sufficient_contrast?(p)
      # tested with the few examples: spec/samples/rm0x.jpeg
      p.stddev > 20
    end
  end
end


# def edgy?(x, y)
#   tol = 5
#   (x < tol) or (y < tol) or (y > @height - tol) or (x > @width - tol)
# end
#
# def patch
#   @the_npatch ||= blurry_narr.reshape!(@width, @height)
# end
#
# def narr
#   NArray[@mim.pixels]
# end
#
# def blurry_narr
#   @blurry_narr ||= NArray[@mim.blur!(10,5).pixels]
# end
#

Version data entries

2 entries across 2 versions & 1 rubygems

Version	Path
mork-0.3.0	lib/mork/npatch.rb
mork-0.2.1	lib/mork/npatch.rb