Add external python modules examples

These examples will be used at the QtWS2019:
- Matplotlib: Widget interacting with a 3D plot
- OpenCV: Webcam pattern detection
- Scikit Image: Image filters

An About Qt section was added to all examples.

Change-Id: I14da69c9b5ecdc8409bcdb335135a8b1fa763bb1
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 207 insertions, 0 deletions

diff --git a/examples/external/opencv/requirements.txt b/examples/external/opencv/requirements.txt
new file mode 100644
index 000000000..0dd006bbc
--- /dev/null
+++ b/examples/external/opencv/requirements.txt
@@ -0,0 +1 @@
+opencv-python
diff --git a/examples/external/opencv/webcam_pattern_detection.py b/examples/external/opencv/webcam_pattern_detection.py
new file mode 100644
index 000000000..7c18a9da5
--- /dev/null
+++ b/examples/external/opencv/webcam_pattern_detection.py
@@ -0,0 +1,206 @@
+#############################################################################
+##
+## Copyright (C) 2019 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the Qt for Python examples of the Qt Toolkit.
+##
+## $QT_BEGIN_LICENSE:LGPL$
+## Commercial License Usage
+## Licensees holding valid commercial Qt licenses may use this file in
+## accordance with the commercial license agreement provided with the
+## Software or, alternatively, in accordance with the terms contained in
+## a written agreement between you and The Qt Company. For licensing terms
+## and conditions see https://www.qt.io/terms-conditions. For further
+## information use the contact form at https://www.qt.io/contact-us.
+##
+## GNU Lesser General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU Lesser
+## General Public License version 3 as published by the Free Software
+## Foundation and appearing in the file LICENSE.LGPL3 included in the
+## packaging of this file. Please review the following information to
+## ensure the GNU Lesser General Public License version 3 requirements
+## will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 2.0 or (at your option) the GNU General
+## Public license version 3 or any later version approved by the KDE Free
+## Qt Foundation. The licenses are as published by the Free Software
+## Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-2.0.html and
+## https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import os
+import sys
+import time
+
+import cv2
+from PySide2.QtCore import Qt, QThread, Signal, Slot
+from PySide2.QtGui import QImage, QKeySequence, QPixmap
+from PySide2.QtWidgets import (QAction, QApplication, QComboBox, QGroupBox,
+                               QHBoxLayout, QLabel, QMainWindow, QPushButton,
+                               QSizePolicy, QVBoxLayout, QWidget)
+
+
+"""This example uses the video from a  webcam to apply pattern
+detection from the OpenCV module. e.g.: face, eyes, body, etc."""
+
+
+class Thread(QThread):
+    updateFrame = Signal(QImage)
+
+    def __init__(self, parent=None):
+        QThread.__init__(self, parent)
+        self.trained_file = None
+        self.status = True
+        self.cap = True
+
+    def set_file(self, fname):
+        # The data comes with the 'opencv-python' module
+        self.trained_file = os.path.join(cv2.data.haarcascades, fname)
+
+    def run(self):
+        self.cap = cv2.VideoCapture(0)
+        while self.status:
+            cascade = cv2.CascadeClassifier(self.trained_file)
+            ret, frame = self.cap.read()
+            if not ret:
+                continue
+
+            # Reading frame in gray scale to process the pattern
+            gray_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
+
+            detections = cascade.detectMultiScale(gray_frame, scaleFactor=1.1,
+                                                  minNeighbors=5, minSize=(30, 30))
+
+            # Drawing green rectangle around the pattern
+            for (x, y, w, h) in detections:
+                pos_ori = (x, y)
+                pos_end = (x + w, y + h)
+                color = (0, 255, 0)
+                cv2.rectangle(frame, pos_ori, pos_end, color, 2)
+
+            # Reading the image in RGB to display it
+            color_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
+
+            # Creating and scaling QImage
+            h, w, ch = color_frame.shape
+            img = QImage(color_frame.data, w, h, ch * w, QImage.Format_RGB888)
+            scaled_img = img.scaled(640, 480, Qt.KeepAspectRatio)
+
+            # Emit signal
+            self.updateFrame.emit(scaled_img)
+        sys.exit(-1)
+
+
+class Window(QMainWindow):
+    def __init__(self):
+        QMainWindow.__init__(self)
+        # Title and dimensions
+        self.setWindowTitle("Patterns detection")
+        self.setGeometry(0, 0, 800, 500)
+
+        # Main menu bar
+        self.menu = self.menuBar()
+        self.menu_file = self.menu.addMenu("File")
+        exit = QAction("Exit", self, triggered=qApp.quit)
+        self.menu_file.addAction(exit)
+
+        self.menu_about = self.menu.addMenu("&About")
+        about = QAction("About Qt", self, shortcut=QKeySequence(QKeySequence.HelpContents),
+                        triggered=qApp.aboutQt)
+        self.menu_about.addAction(about)
+
+        # Create a label for the display camera
+        self.label = QLabel(self)
+        self.label.setFixedSize(640, 480)
+
+        # Thread in charge of updating the image
+        self.th = Thread(self)
+        self.th.finished.connect(self.close)
+        self.th.updateFrame.connect(self.setImage)
+
+        # Model group
+        self.group_model = QGroupBox("Trained model")
+        self.group_model.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)
+        model_layout = QHBoxLayout()
+
+        self.combobox = QComboBox()
+        for xml_file in os.listdir(cv2.data.haarcascades):
+            if xml_file.endswith(".xml"):
+                self.combobox.addItem(xml_file)
+
+        model_layout.addWidget(QLabel("File:"), 10)
+        model_layout.addWidget(self.combobox, 90)
+        self.group_model.setLayout(model_layout)
+
+        # Buttons layout
+        buttons_layout = QHBoxLayout()
+        self.button1 = QPushButton("Start")
+        self.button2 = QPushButton("Stop/Close")
+        self.button1.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)
+        self.button2.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.Expanding)
+        buttons_layout.addWidget(self.button2)
+        buttons_layout.addWidget(self.button1)
+
+        right_layout = QHBoxLayout()
+        right_layout.addWidget(self.group_model, 1)
+        right_layout.addLayout(buttons_layout, 1)
+
+        # Main layout
+        layout = QVBoxLayout()
+        layout.addWidget(self.label)
+        layout.addLayout(right_layout)
+
+        # Central widget
+        widget = QWidget(self)
+        widget.setLayout(layout)
+        self.setCentralWidget(widget)
+
+        # Connections
+        self.button1.clicked.connect(self.start)
+        self.button2.clicked.connect(self.kill_thread)
+        self.button2.setEnabled(False)
+        self.combobox.currentTextChanged.connect(self.set_model)
+
+    @Slot()
+    def set_model(self, text):
+        self.th.set_file(text)
+
+    @Slot()
+    def kill_thread(self):
+        print("Finishing...")
+        self.button2.setEnabled(False)
+        self.button1.setEnabled(True)
+        self.th.cap.release()
+        cv2.destroyAllWindows()
+        self.status = False
+        self.th.terminate()
+        # Give time for the thread to finish
+        time.sleep(1)
+
+    @Slot()
+    def start(self):
+        print("Starting...")
+        self.button2.setEnabled(True)
+        self.button1.setEnabled(False)
+        self.th.set_file(self.combobox.currentText())
+        self.th.start()
+
+    @Slot(QImage)
+    def setImage(self, image):
+        self.label.setPixmap(QPixmap.fromImage(image))
+
+
+if __name__ == "__main__":
+    app = QApplication()
+    w = Window()
+    w.show()
+    sys.exit(app.exec_())