1.3 应用结合1.1 和1.2 处理某个文件夹'Icons-dp'下所有PNG-把PNG文件透明边白色，然后沿有效图形剪切

原理：参考1.1和1.2

import cv2
import os
import numpy as np


def alpha2white_opencv2(img):
    sp = img.shape
    width = sp[0]
    height = sp[1]
    for yh in range(height):
        for xw in range(width):
            color_d = img[xw, yh]
            if color_d[3] != 255:  # 找到alpha通道不為255的像素
                img[xw, yh] = [255, 255, 255, 255]  # 改變這個像素
    return img


def cut_img(img, full_file_path_to_save):
    loc = np.where(img < 255)  # 内容为非白色部分（有意义部分）
    lx = []
    ly = []
    for pt in zip(*loc[::-1]):  # pt 为每个像素点的坐标
        lx.append(pt[1])
        ly.append(pt[2])
    sx = min(lx)
    bx = max(lx)
    sy = min(ly)
    by = max(ly)
    cv2.imwrite(full_file_path_to_save, img[sy:by, sx:bx])  # 保存时只保留有意义部分


if __name__ == '__main__':

    filePath = 'Icons-dp/'
    file_name_list = []
    for i, j, k in os.walk(filePath):
        file_name_list = k
    for file in file_name_list:
        full_file_path = filePath + file
        image = cv2.imread(full_file_path, cv2.IMREAD_UNCHANGED)  # 第二个参数保留Alpha通道
        image = alpha2white_opencv2(image)
        cut_img(image, 'd' + full_file_path)  # 確認路徑'dIcons-dp' 存在，如不存在程序不會報錯也不會寫入圖片