Fine. Our filter classes are implemented, and we can now create our custom widget. This widget will take as inputs: a source picture and a thumbnail picture. Then the thumbnail will be immediately processed to display a preview of the filter. If the user clicks on the widget, it will process the source picture and trigger a signal with the filtered picture. Keep in mind that this widget will later be dragged and dropped in the Form Editor of Qt Creator. That's why we will provide properties with getters and setters to select a filter from Qt Creator. Let's create a new widget called FilterWidget using the Qt Designer Form Class template. The FilterWidget.ui is really simple, as you can see in the following screenshot:
The titleLabel is a QLabel on top of the QWidget. In the following code, thumbnailLabel will display the filtered...