Fun with Gabor Filters


Written by:

Robert McIntyre

Gabor filters were invented by the same guy who invented holograms.

They work well as edge detectors and are related to the human visual system.

(ns cortex.gabor
  (:import org.opencv.core.CvType)
  (:import java.awt.image.BufferedImage)
  (:import ij.ImagePlus)
  (:import org.opencv.core.Mat)
  (:use (cortex world sense util vision import))
  (:import (com.jme3.util BufferUtils Screenshots))
  (:import java.nio.ByteBuffer)
  (:import java.awt.image.BufferedImage)
  (:import (com.jme3.renderer ViewPort Camera))
  (:import (com.jme3.math ColorRGBA Vector3f Matrix3f Vector2f))
  (:import com.jme3.renderer.Renderer)
  (:import com.jme3.texture.FrameBuffer)
  (:import (com.jme3.scene Node Spatial)))

(use  'clojure.math.numeric-tower)
(defn load-opencv
  "Load the opencv native library. Must be called before any OpenCV
  stuff is used."
  (clojure.lang.RT/loadLibrary "opencv_java249"))


(defn gabor-kernel
 ([sigma wavelength theta]
     (gabor-kernel sigma wavelength theta 1 0))
  ([sigma wavelength]
     (gabor-kernel sigma wavelength 0 1 0))
  ([sigma wavelength theta aspect-ratio phase-offset]
  ;; first, find the size of the kernel which is required
  (let [square #(expt % 2)
        rotated (fn [[x y]]
                  [(+ (* x (Math/cos theta)) (* y (Math/sin theta)))
                   (- (* y (Math/cos theta))  (* x (Math/sin theta)))])
        gaussian (fn [[x y]]
                   (let [[x' y'] (rotated [x y])]
                     (Math/exp (- (/ (+ (square x')
                                        (square (* aspect-ratio y')))
                                   (* 2 (square sigma)))))))
        sinusoid (fn [[x y]]
                   (let [[x' y'] (rotated [x y])]
                      (+ (* 2 Math/PI (/ x' wavelength))

        (let [std-dev-capture 5]
           (int (* std-dev-capture (/ sigma aspect-ratio)))
           (int (* std-dev-capture sigma))
           (int (* std-dev-capture (/ aspect-ratio sigma)))))

        grid (let [axis (range (- half-width) (inc half-width))]
               (for [y (reverse axis) x axis] (vector x y)))

        scale (reduce + (map gaussian grid))
        gabor (fn [[x y :as coord]]
                (* (sinusoid coord) (gaussian coord) (/ scale)))

        mat-width (+ 1 (* 2 half-width))
        mat (Mat. mat-width mat-width CvType/CV_32F)]
    (.put mat 0 0 (float-array (map gabor grid)))

(defn draw-kernel! [kernel img-path]
  (let [output img-path
        size (.size kernel)
        width (int (.width size))
        height (int (.height size))
        tmp-array (float-array (* width height))]

    ;; read values from matrix.
    (.get kernel 0 0 tmp-array)

    ;; find overall dynamic range of the filter
    (let [vals (vec tmp-array)
          low (apply min vals)
          high (apply max vals)
          scaled-vals (map #(* 255 (- % low) (/ (- high low))) vals)
          new-mat (Mat. height width CvType/CV_32F)]
      (.put new-mat 0 0 (float-array scaled-vals))
      (org.opencv.highgui.Highgui/imwrite output new-mat))))

;; some cool examples


(def img-base "/home/r/proj/cortex/images/")

(draw-kernel! (gabor-kernel 50 10 0 1 0)
              (str img-base "gabor-50-10.png"))


(draw-kernel! (gabor-kernel 50 10 (/ Math/PI 4) 1 0)
              (str img-base "gabor-50-10-pi-over-4.png"))


(draw-kernel! (gabor-kernel 50 10 (/ Math/PI 2) 1 0)
              (str img-base "gabor-50-10-pi-over-2.png"))


(draw-kernel! (gabor-kernel 50 50 0 1 0)
              (str img-base "gabor-50-50.png"))


(draw-kernel! (gabor-kernel 50 10 0 3 0)
              (str img-base "gabor-50-10-0-3.png"))


(draw-kernel! (gabor-kernel 50 4 (/ Math/PI 3) 3 0)
              (str img-base "gabor-50-4-pi-over3-3.png"))
(defn show-kernel [kernel]
  (let [img-path "/home/r/proj/cortex/tmp/kernel.png"]
    (draw-kernel! kernel img-path)
    (view (ImagePlus. img-path))))

(defn print-kernel [kernel]
  (println (.dump kernel)))

(import com.aurellem.capture.Capture)


(def base "/home/r/proj/cortex/render/gabor-1/")

(defn brick-wall-game-run [record?]
  (let [capture-dir (File. base "main")]
    (.mkdir (File. base "main"))
         (doto (Node.) (.attachChild (floor*))
               (.attachChild (brick-wall*))
         {"key-f" (fn [game value] 
                    (if (not value) (add-element game (brick-wall*))))
          "key-space" (fire-cannon-ball )}
         (fn [world]
            (Vector3f. 1.382548, 4.0383573, 5.994235)
            (Quaternion. 0.0013082094, 0.98581666,
                         -0.1676442, 0.0076932586))

           ;;(speed-up world)
           (if record?
              world capture-dir))
           (add-camera! world (.getCamera world) no-op))
         (fn [& _]))     

(defn convolve-preview [kernel]
  (let [input "/home/r/proj/cortex/render/gabor-1/main/0000032.png"
        output "/home/r/ppp.png"

        i (org.opencv.highgui.Highgui/imread input)

        ;;kernel (gabor-kernel 10 1 (/ Math/PI 2) 10 0)

        new-mat (Mat.)

     i new-mat CvType/CV_32F kernel)
    (org.opencv.highgui.Highgui/imwrite "/home/r/ppp.png" new-mat)
    (view (ImagePlus. input))
    (view (ImagePlus. output))))

(use '

(defn apply-gabor [kernel source dest]
    (let [i (org.opencv.highgui.Highgui/imread source)
          new-mat (Mat.)]
      (println dest)
      (if (not (.exists (File. dest)))
           i new-mat CvType/CV_32F kernel)
          (org.opencv.highgui.Highgui/imwrite dest new-mat)
          (println "mogrify" "-modulate" "1000%" dest)
          (sh "mogrify" "-modulate" "1000%" dest)))))


(defn images [path]
  (sort (rest (file-seq (File. path)))))

(defn pics [file]
  (images (str base file)))

(defn generate-gabor-images [kernel name]
  (draw-kernel! kernel (str base name ".png"))

  (.mkdir (File. (str base name)))
  (let [main (map #(.getCanonicalPath %) (pics "main"))
        targets (map #(str base name "/" (format "%07d.png" %))
                     (range 0 (count main)))]
    (dorun (pmap (partial apply-gabor kernel) main targets))))

(def banks
  [[(gabor-kernel 2.8 3.5) "bank-1-1"]
   [(gabor-kernel 2.8 3.5 (/ Math/PI 2)) "bank-1-1-rot"]
;;   [(gabor-kernel 3.6 4.6) "bank-1-2"]
;;   [(gabor-kernel 4.5 5.6) "bank-2-1"]
;;   [(gabor-kernel 6.3 7.9) "bank-3-1"]
;;   [(gabor-kernel 7.3 9.1) "bank-3-2"]

   [(gabor-kernel 12.3 15.4) "bank-6-1"]

;;   [(gabor-kernel 17 21.2) "bank-8-1"]
;;   [(gabor-kernel 18.2 22.8) "bank-8-2"]

(defn make-all-images []
  (dorun (map (partial apply generate-gabor-images) banks)))

(defn compile-left-right []
  (.mkdir (File. (str base "left-right")))
  (let [main (pics "main")
        left (pics "bank-1-1")
        right (pics "bank-1-1-rot")
        left-kernel (repeat 20000 (File. (str base "bank-1-1.png")))
        right-kernel (repeat 20000 (File. (str base "bank-1-1-rot.png")))
        targets (map
                 #(File. (str base "left-right/" (format "%07d.png" %)))
                 (range 0 (count main)))]
       (fn [[main left right left-kernel right-kernel target]]
         (println target)
         (if (not (.exists (File. target)))
           (sh "convert"
               "-size" "1940x515" "xc:white"
               main      "-geometry" "+0+0"    "-composite"
               left "-geometry" "+650+0"   "-composite"
               right     "-geometry" "+1300+0"  "-composite"
               left-kernel      "-geometry" "+960+485"  "-composite"
               right-kernel      "-geometry" "+1610+485"  "-composite"
       (fn [& args] (map #(.getCanonicalPath %) args)))
      main left right left-kernel right-kernel targets))))

(defn compile-big-small []
  (.mkdir (File. (str base "big-small")))
  (let [main (pics "main")
        left (pics "bank-1-1")
        right (pics "bank-6-1")
        small-kernel (repeat 20000 (File. (str base "bank-1-1.png")))
        big-kernel (repeat 20000 (File. (str base "bank-6-1.png")))
        targets (map
                 #(File. (str base "big-small/" (format "%07d.png" %)))
                 (range 0 (count main)))]
       (fn [[main left right small-kernel big-kernel target]]
         (println target)
         (if (not (.exists (File. target)))
           (sh "convert"
               "-size" "1940x610" "xc:white"
               main      "-geometry" "+0+0"    "-composite"
               left "-geometry" "+650+0"   "-composite"
               right     "-geometry" "+1300+0"  "-composite"
               small-kernel      "-geometry" "+960+485"  "-composite"
               big-kernel      "-geometry" "+1560+485"  "-composite"
       (fn [& args] (map #(.getCanonicalPath %) args)))
      main left right small-kernel big-kernel targets))))

(defn regen-everything []
        ffmpeg -framerate 60 -i ./big-small/%07d.png -b:v 9000k\
            -c:v theora -r 60 gabor-scale.ogg

        ffmpeg -framerate 60 -i ./left-right/%07d.png -b:v 9000k\
            -c:v theora -r 60 gabor-rotation.ogg

all: rotation scale

        rm gabor-scale.ogg


Two gabor filters with different values of theta are compared. The horizontally aligned one does better in this example.


Here we compare a gabor filter from bank 1 with one from bank 6.

1 Source Listing

Author: Robert McIntyre

Created: 2015-04-19 Sun 07:04

Emacs 24.4.1 (Org mode 8.3beta)