ADD image preview for file selection dialog

gui.py

+from preview import QFileDialogPreview
 import base64
 import importlib.util
 import os
@@ -17,6 +18,7 @@ from matplotlib.figure import Figure
 
 import tool_widget
 
+
 MAINWINDOW, _ = uic.loadUiType('crack_util.ui')
 
 SETTINGS_IMAGE_PATH = 'settings/image_path'
@@ -173,10 +175,16 @@ class CrackUtility(QtWidgets.QMainWindow, MAINWINDOW):
 
     def open_image(self):
         last_path = self.settings.value(SETTINGS_IMAGE_PATH, '', type=str)
-        file_name, pattern = QtWidgets.QFileDialog.getOpenFileName(
-            self, 'Open image', last_path,
-            "Image files (*.jpg *.jpeg *.png *.JPG);;All files (*)")
-        if file_name == '':
+        #file_name, pattern = QtWidgets.QFileDialog.getOpenFileName(
+        #    self, 'Open image', last_path,
+        #    "Image files (*.jpg *.jpeg *.png *.JPG);;All files (*)")
+        file_dialog = QFileDialogPreview(self, 'Open image', last_path,
+                                         "Image Files (*.png *.jpg *.jpeg *.bmp *.tif);;All files (*)")
+        file_dialog.setAcceptMode(QtWidgets.QFileDialog.AcceptOpen)
+        file_dialog.exec()
+        file_name = file_dialog.getFileSelected()
+        if file_name is None or file_name == '':
+            print("No file selected")
             return
         self.settings.setValue(SETTINGS_IMAGE_PATH, os.path.dirname(file_name))
         self.settings.sync()

preview.py

+from PyQt5 import QtCore, QtWidgets, QtGui
+
+class QFileDialogPreview(QtWidgets.QFileDialog):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.setOption(QtWidgets.QFileDialog.DontUseNativeDialog, True)
+        box = QtWidgets.QVBoxLayout()
+        self.setFixedSize(self.width() + 350, self.height())
+        self.mpPreview = QtWidgets.QLabel("Preview", self)
+        self.mpPreview.setFixedSize(350, 250)
+        self.mpPreview.setAlignment(QtCore.Qt.AlignCenter)
+        self.mpPreview.setObjectName("labelPreview")
+        box.addWidget(self.mpPreview)
+        
+        box.addStretch()
+        
+        self.layout().addLayout(box, 1, 3, 1, 1)
+        self.currentChanged.connect(self.onChange)
+        self.fileSelected.connect(self.onFileSelected)
+        self.filesSelected.connect(self.onFilesSelected)
+        self._fileSelected = None
+        self._filesSelected = None
+        
+    def onChange(self, path):
+        pixmap = QtGui.QPixmap(path)
+        if pixmap.isNull():
+            self.mpPreview.setText("Preview")
+        else:
+            self.mpPreview.setPixmap(pixmap.scaled(self.mpPreview.width(),
+                                                   self.mpPreview.height(),
+                                                   QtCore.Qt.KeepAspectRatio,
+                                                   QtCore.Qt.SmoothTransformation))
+    
+    def onFileSelected(self, file):
+        self._fileSelected = file
+    
+    def onFilesSelected(self, files):
+        self._filesSelected = files
+    
+    def getFileSelected(self):
+        return self._fileSelected
+    
+    def getFilesSelected(self):
+        return self._filesSelected