Python實現圖像直方圖均衡化算法

---

title: "Python實現圖像直方圖均衡化算法"
date: 2018-06-12T17:10:48+08:00
tags: [""]
categories: ["python"]

---

效果圖

代碼

#!/usr/bin/env python3
# coding=utf-8

import matplotlib.image as mpimg
from matplotlib import pyplot as plt
import sys
import numpy as np


def equalization(gray_value):
    """
    傳入灰度值，對灰度值做均衡化，不需要返回，直接修改傳入的參數
    :param gray_value:
    """
    # 統計灰度直方圖
    gray = np.zeros(256)
    row, column = gray_value.shape
    for i in range(row):
        for j in range(column):
            gray[gray_value[i][j]] += 1

    # 計算灰度占比
    gray /= (row * column)
    # 顯示灰度直方圖
    plt.subplot(2, 2, 2)
    plt.plot(gray)

    cumsum = np.cumsum(gray)  # 計算累積和

    # 均衡化
    # equa_t[i]=j表示原灰度值i經過均衡化后轉化為灰度值j
    # 255×累積和四舍五入為int型
    equa_t = np.array((255 * cumsum + 0.5)).astype(np.int32)
    # 統計均衡化后的灰度數量
    equa_gray = np.zeros(256)
    for i in range(256):
        equa_gray[equa_t[i]] += gray[i]
    # 顯示均衡化后的直方圖
    plt.subplot(2, 2, 4)
    plt.plot(equa_gray)
    # 對原灰度矩陣做均衡化
    for i in range(row):
        for j in range(column):
            gray_value[i][j] = equa_t[gray_value[i][j]]


def run(img_path):
    img_array = mpimg.imread(img_path)
    plt.subplot(2, 2, 1)
    plt.imshow(img_array)
    img_array *= 255
    img_array = img_array.astype(np.int32)
    equalization(img_array[:, :, 0])
    equalization(img_array[:, :, 1])
    equalization(img_array[:, :, 2])
    img_array = img_array.astype(np.float64)
    img_array /= 255
    plt.subplot(2, 2, 3)
    plt.imshow(img_array)


if __name__ == "__main__":
    if sys.argv.__len__() <= 1:
        png = input("請輸入要處理的圖片名:\n")
    else:
        png = sys.argv[1]
    run(png)
    plt.show()