add qt video example (#341)

kushalkolar · web-flow · commit 221a20c9e073 · 2023-10-26T13:56:11.000-04:00
diff --git a/examples/qt/video.py b/examples/qt/video.py
@@ -0,0 +1,57 @@
+"""
+Use a simple Plot to display a video frame that can be updated using a QSlider
+"""
+from PyQt6 import QtWidgets, QtCore
+import fastplotlib as fpl
+import imageio.v3 as iio
+
+# Qt app MUST be instantiated before creating any fpl objects, or any other Qt objects
+app = QtWidgets.QApplication([])
+
+video = iio.imread("imageio:cockatoo.mp4")
+
+# force qt canvas, wgpu will sometimes pick glfw by default even if Qt is present
+plot = fpl.Plot(canvas="qt")
+
+plot.add_image(video[0], name="video")
+plot.camera.local.scale *= -1
+
+
+def update_frame(ix):
+    plot["video"].data = video[ix]
+    # you can also do plot.graphics[0].data = video[ix]
+
+
+# create a QMainWindow, set the plot canvas as the main widget
+# The canvas does not have to be in a QMainWindow and it does
+# not have to be the central widget, it will work like any QWidget
+main_window = QtWidgets.QMainWindow()
+main_window.setCentralWidget(plot.canvas)
+
+# Create a QSlider for updating frames
+slider = QtWidgets.QSlider(QtCore.Qt.Orientation.Horizontal)
+slider.setMaximum(video.shape[0] - 1)
+slider.setMinimum(0)
+slider.valueChanged.connect(update_frame)
+
+# put slider in a dock
+dock = QtWidgets.QDockWidget()
+dock.setWidget(slider)
+
+# put the dock in the main window
+main_window.addDockWidget(
+    QtCore.Qt.DockWidgetArea.BottomDockWidgetArea,
+    dock
+)
+
+# calling plot.show() is required to start the rendering loop
+plot.show()
+
+# set window size from width and height of video
+main_window.resize(video.shape[2], video.shape[1])
+
+# show the main window
+main_window.show()
+
+# execute Qt app
+app.exec()
