Median Filter

median_filter.py

# -*- coding:utf-8 -*-

from PIL import Image
from itertools import product

class Filter:
    def __init__(self, input_image):
        self.input_image = input_image
        self.input_pix = self.input_image.load()
        self.w, self.h = self.input_image.size
    def median(self):
        output_image = Image.new("RGB", self.input_image.size)
        output_pix = output_image.load()

        # ピクセルの周辺走査用変数
        W = (-1, 2)
        H = (-1, 2)

        # 配列の境界判定
        borderX = {0: (0, 2), self.w-1: (-1, 1)}
        borderY = {0: (0, 2), self.h-1: (-1, 1)}

        for y, x in product(*map(xrange, (self.h, self.w))):
            pixels = []
            _W, _H = W, H

            if not 0 < x < self.w - 1:
                _W = borderX[x]
            if not 0 < y < self.h - 1:
                _H = borderY[y]

            # x, y周辺の輝度を得る
            for dx, dy in product(range(*_W), range(*_H)):
                pixel = self.input_pix[x+dx, y+dy]
                pixels.append(pixel)

            # 輝度配列の長さ
            pixlen = len(pixels)

            # 色成分ごとに配列をまとめる
            pixels = zip(*pixels)

            # 輝度順にソートする
            sorted_pixels = map(sorted, pixels)

            # 中央値を得る
            color = tuple(map(lambda x: x[int(pixlen/2)], sorted_pixels))
            output_pix[x, y] = color
        return output_image

input_img = Image.open("input.jpg")
filterInstance = Filter(input_img)
output_img = filterInstance.median()
output_img.save("output.jpg","JPEG")