QT多张图片的重叠显示

QT 中可以加载显示多张图片，如果同时显示多张图片，并且显示图片重叠的效果，就要使用CompositionMode了。

注意：设置模式只能设置图片!

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
class QImage;namespace Ui {
class MainWindow;
}class MainWindow : public QMainWindow
{Q_OBJECTpublic:explicit MainWindow(QWidget *parent = 0);~MainWindow();void paintEvent(QPaintEvent *event)override;private:Ui::MainWindow *ui;QImage* firstImage=nullptr;QImage* secondImage=nullptr;
};#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QPainter>
#include <QImage>MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow){ui->setupUi(this);firstImage = new QImage(500,500,QImage::Format_ARGB32_Premultiplied);secondImage = new QImage(500,500,QImage::Format_ARGB32_Premultiplied);
}MainWindow::~MainWindow(){delete ui;
}void MainWindow::paintEvent(QPaintEvent *event){//绘制第一张图片QPainter painterFirst(firstImage);firstImage->fill(Qt::transparent);//设置透明painterFirst.setBrush(Qt::red);painterFirst.drawRect(50,50,100,100);//绘制第二张图片QPainter painterSecond(secondImage);secondImage->fill(Qt::transparent);painterSecond.setBrush(Qt::blue);painterSecond.drawRect(100,100,100,100);//设置图片的重叠模式painterFirst.setCompositionMode(QPainter::CompositionMode_SourceOver);//重叠图片painterFirst.drawImage(0, 0, *secondImage);//展示图片QPainter painter2(this);painter2.drawImage(0,0,*firstImage);
}

以下是几种重叠模式效果图：
CompositionMode_Source

CompositionMode_Destination

CompositionMode_SourceOver

CompositionMode_DestinationOver

CompositionMode_SourceIn

CompositionMode_DestinationIn

CompositionMode_Plus

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