Qt not only allows us to draw shapes and images on screen, but it also allows us to overlay multiple images on top of each other and combine the pixel information from all the layers using different types of algorithms to create very interesting results. In this example, we will learn how to overlay images on top of each other and apply different composition effects to them.
Let's create a simple demo that shows the effect of different image compositions by following these steps:
First, set up a new Qt Widgets Application project and remove the menu bar, tool bar, and status bar.
Next, add the QPainter class header to
mainwindow.h:#include <QPainter>
After that, declare the
paintEvent()virtual function like so:virtual void paintEvent(QPaintEvent* event);
In
mainwindow.cpp, we will first load several image files using theQImageclass:void MainWindow::paintEvent(QPaintEvent* event) { QImage image; image.load("checker.png"); QImage image2;...