---

import os
from PyQt5.QtWidgets import (
   QApplication, QWidget,
   QFileDialog, # Диалог открытия файлов (и папок)
   QLabel, QPushButton, QListWidget,
   QHBoxLayout, QVBoxLayout
)
from PyQt5.QtCore import Qt # нужна константа Qt.KeepAspectRatio для изменения размеров с сохранением пропорций
from PyQt5.QtGui import QPixmap # оптимизированная для показа на экране картинка


from PIL import Image


app = QApplication([])
win = QWidget()       
win.resize(700, 500) 
win.setWindowTitle('Easy Editor')
lb_image = QLabel("Картинка")
btn_dir = QPushButton("Папка")
lw_files = QListWidget()


btn_left = QPushButton("Лево")
btn_right = QPushButton("Право")
btn_flip = QPushButton("Зеркало")
btn_sharp = QPushButton("Резкость")
btn_bw = QPushButton("Ч/Б")


row = QHBoxLayout()          # Основная строка
col1 = QVBoxLayout()         # делится на два столбца
col2 = QVBoxLayout()
col1.addWidget(btn_dir)      # в первом - кнопка выбора директории
col1.addWidget(lw_files)     # и список файлов
col2.addWidget(lb_image, 95) # вo втором - картинка
row_tools = QHBoxLayout()    # и строка кнопок
row_tools.addWidget(btn_left)
row_tools.addWidget(btn_right)
row_tools.addWidget(btn_flip)
row_tools.addWidget(btn_sharp)
row_tools.addWidget(btn_bw)
col2.addLayout(row_tools)


row.addLayout(col1, 20)
row.addLayout(col2, 80)
win.setLayout(row)


win.show()


workdir = ''


def filter(files, extensions):
   result = []
   for filename in files:
       for ext in extensions:
           if filename.endswith(ext):
               result.append(filename)
   return result


def chooseWorkdir():
   global workdir
   workdir = QFileDialog.getExistingDirectory()


def showFilenamesList():
   extensions = ['.jpg','.jpeg', '.png', '.gif', '.bmp']
   chooseWorkdir()
   filenames = filter(os.listdir(workdir), extensions)


   lw_files.clear()
   for filename in filenames:
       lw_files.addItem(filename)


btn_dir.clicked.connect(showFilenamesList)


class ImageProcessor():
   def __init__(self):
       self.image = None
       self.dir = None
       self.filename = None
       self.save_dir = "Modified/"


   def loadImage(self, dir, filename):
       ''' при загрузке запоминаем путь и имя файла '''
       self.dir = dir
       self.filename = filename
       image_path = os.path.join(dir, filename)
       self.image = Image.open(image_path)


   def do_bw(self):
       self.image = self.image.convert("L")
       self.saveImage()
       image_path = os.path.join(self.dir, self.save_dir, self.filename)
       self.showImage(image_path)


   def saveImage(self):
       ''' сохраняет копию файла в подпапке '''
       path = os.path.join(self.dir, self.save_dir)
       if not(os.path.exists(path) or os.path.isdir(path)):
           os.mkdir(path)
       image_path = os.path.join(path, self.filename)
       self.image.save(image_path)


   def showImage(self, path):
      pixmapimage = QPixmap(path)
      label_width, label_height = lb_image.width(), lb_image.height()
      scaled_pixmap = pixmapimage.scaled(label_width, label_height, Qt.KeepAspectRatio)
      lb_image.setPixmap(scaled_pixmap)
      lb_image.setVisible(True)


def showChosenImage():
    if lw_files.currentRow() >= 0:
        filename = lw_files.currentItem().text()
        workimage.loadImage(workdir, filename)
        image_path = os.path.join(workimage.dir, workimage.filename)
        workimage.showImage(image_path)




workimage = ImageProcessor() #текущая рабочая картинка для работы
lw_files.currentRowChanged.connect(showChosenImage)


btn_bw.clicked.connect(workimage.do_bw)


app.exec()