PRML §8.3.3

add_noise.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# add_noise.py - 割合を指定して画像にノイズを付加
#
# usage: python add_noise.py <orig> <noise-rate> [<output>]
#
import sys
import random

import Image # PIL
from myutil import save_or_show


# 正確に noise_rate の分だけノイズを入れる
def add_noise(img_orig, noise_rate):
    width, height = img.size
    S = width * height
    n = int(S * noise_rate + 0.5)

    to_toggle = [False] * S
    for i in range(n): to_toggle[i] = True
    random.shuffle(to_toggle)

    pix = img.load()
    for y in range(height):
        for x in range(width):
            i = y * width + x
            if to_toggle[i]:
                pix[x,y] = 255 - pix[x,y]
    return img


# 確率的にノイズを入れるので noise_rate とすこし離れる
def add_noise0(img_orig, noise_rate):
    width, height = img.size
    pix = img.load()
    for y in range(height):
        for x in range(width):
            if random.random() < noise_rate:
                pix[x,y] = 255 - pix[x,y]
    return img


if __name__ == '__main__':
    if len(sys.argv) < 3:
        print "usage: python %s <orig> <noise-rate> [<output>]" % sys.argv[0]
        sys.exit()

    infile = sys.argv[1]
    noise_rate = float(sys.argv[2]) / 100
    if len(sys.argv) == 4:
        outfile = sys.argv[3]
    else:
        outfile = None

    img = Image.open(infile)
    img2 = add_noise(img, noise_rate)
    save_or_show(img2, outfile)

make_image.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# make_image.py - 元画像を作成
#
# usage: python make_noise.py [<output>]
#
import sys

import Image
import ImageDraw
import ImageFont

from myutil import save_or_show

if __name__ == '__main__':
    img = Image.new('1', (320, 180), "white")

    # font = ImageFont.truetype('/Library/Fonts/MovieFont-Home.ttf', 48, encoding='utf-8')
    font = ImageFont.truetype('/Library/Fonts/sazanami-gothic.ttf', 48, encoding='utf-8')
    draw = ImageDraw.Draw(img)
    draw.text((20, 20), u'ぷるむる', font=font, fill='black')
    draw.text((20, 100), u'復々習レーン', font=font, fill='black')

    if len(sys.argv) == 2:
        outfile = sys.argv[1]
    else:
        outfile = None
    save_or_show(img, outfile)

myutil.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# myutil.py
#
import sys
import os
import time

import Image # PIL

def save_or_show(img, outfile=None):
    if outfile:
        img.save(outfile)
    else:
        outfile = "myutil_tmp.png"
        img.save(outfile)
        os.system("open %s" % outfile)
        time.sleep(1)
        os.system("rm -f %s" % outfile)

remove_noise.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# remove_noise.py - ノイズを除去する
#
# usage: python remove_noise.py <input> [<output>]
#
import sys
import os

import Image # PIL
from myutil import save_or_show

H = 0.01
BETA = 0.1
ETA = 0.1
EPS = 1e-5

def E(xs, ys, width, height):
    S = width * height

    s0 = s1 = s2 = 0

    for i in range(S):
        s0 += xs[i]
        s2 += xs[i] * ys[i]

    for y in range(height-1):
        for x in range(width-1):
            i = y*width + x
            s1 += xs[i] * xs[i+1] + xs[i] * xs[i+width]

    e = H * s0 - BETA * s1 - ETA * s2
    return e


def remove_noise(img):
    width, height = img.size
    S = width * height

    pix = img.load()
    xs = [0]*S
    ys = [0]*S
    for x in range(width):
        for y in range(height):
            i = y*width + x
            xs[i] = ys[i] = 1 if pix[x,y] > 0 else -1

    def de(i):
        s0 = xs[i]

        s1 = 0
        if i > 0:
            s1 += xs[i] * xs[i-1]
        if i < S-1:
            s1 += xs[i] * xs[i+1]
        if i >= width:
            s1 += xs[i] * xs[i-width]
        if i < S-width:
            s1 += xs[i] * xs[i+width]

        s2 = xs[i] * ys[i]

        curr_e = H * s0 - BETA * s1 - ETA * s2
        toggled_e = -curr_e

        return toggled_e < curr_e

    def reflect():
        for i in range(S):
            x = i % width
            y = i / width
            pix[x,y] = 255 if xs[i] == 1 else 0

    energy = E(xs, ys, width, height)
    print 0, energy

    for j in range(10):
        for i in range(S):
            if de(i): xs[i] = -xs[i]

        new_energy = E(xs, ys, width, height)
        print 1+j, new_energy

        if energy - new_energy < EPS: break
        energy = new_energy

    reflect()
    return img


if __name__ == '__main__':
    if len(sys.argv) < 2:
        print "usage: python %s <input> [<output>]" % sys.argv[0]
        sys.exit()

    infile = sys.argv[1]
    if len(sys.argv) == 3:
        outfile = sys.argv[2]
    else:
        outfile = None

    img = Image.open(infile)
    img2 = remove_noise(img)
    save_or_show(img2, outfile)

score.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import Image
import numpy as np
import sys

if __name__ == '__main__':
    if len(sys.argv) < 3:
        print "usage: python %s <orig> <noised> <removed>" % sys.argv[0]
        sys.exit()

    img1 = Image.open(sys.argv[1])
    img2 = Image.open(sys.argv[2])
    img3 = Image.open(sys.argv[3])

    width1, height1 = img1.size
    width2, height2 = img2.size
    width3, height3 = img3.size
    if width1 != width2 or height1 != height2 or width1 != width3 or height1 != height3:
        print "0.0 - size mismatch."
        sys.exit()

    pix1 = img1.load()
    pix2 = img2.load()
    pix3 = img3.load()

    res = [0.0] * 8
    for x in range(width1):
        for y in range(height1):
            p1 = 1 if pix1[x,y] == 255 else 0
            p2 = 1 if pix2[x,y] == 255 else 0
            p3 = 1 if pix3[x,y] == 255 else 0
            res[p1*4 + p2*2 + p3] += 1

    # 1*1 0*0
    yes = res[0] + res[2] + res[5] + res[7]
    no = res[1] + res[3] + res[4] + res[6]
    rate = yes / (yes + no)
    print "復元率: %g%%" % (rate * 100)

    # 0*0, 0*1
    ji_yes = res[0] + res[2]
    ji_no = res[1] + res[3]
    ji_rate = ji_yes / (ji_yes + ji_no)
    print "（文字部分復元率: %g%%, " % (ji_rate * 100),

    # 101, 100
    wh_yes = res[5]
    wh_no = res[4]
    wh_rate = wh_yes / (wh_yes + wh_no)
    print "白地部分ノイズ除去率: %g%%）" % (wh_rate * 100)