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QT播放视频保持视频宽高比消除黑边

1、问题

在播放视频的时候，由于框架的大小发生变化，导致视频出现黑边很不好看。
因此需要像一种方法消除黑边

2、处理

1、读取视频的宽高比
2、设置视频的Widget的大小固定，Widget的宽高比和视频宽高比相同。

• cpp文件

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMediaPlayer>
#include <QVideoWidget>
#include <QVBoxLayout>
#include <QPushButton>
#include <QMediaMetaData>void MainWindow::playVideo()
{player->play();
}MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow)
{ui->setupUi(this);QVBoxLayout* qs = new QVBoxLayout();ui->centralwidget->setLayout (qs);// 创建播放器和视频窗口player = new QMediaPlayer;QVideoWidget *videoWidget = new QVideoWidget;// 监听媒体加载完成状态QObject::connect(player, &QMediaPlayer::mediaStatusChanged, [=](QMediaPlayer::MediaStatus status) {if (status == QMediaPlayer::LoadedMedia) {  // 媒体已加载完成// 获取视频分辨率元数据QSize resolution = player->metaData().value(QMediaMetaData::Resolution).toSize();if (!resolution.isEmpty()) {qDebug() << "视频宽高：" << resolution;} else {qDebug() << "未获取到分辨率信息";}int w = resolution.width ();int h = resolution.height ();double r = 1.0 * w / h;int ww = 800;int hh = int(ww / r);qDebug() << ww << " " << hh << " s " << w << " " << h;// 固定宽高比videoWidget->setFixedSize (QSize(ww, hh));}});// 强制拉伸填充窗口（可能变形）videoWidget->setAspectRatioMode(Qt::IgnoreAspectRatio);// 隐藏黑边（设置背景色透明）videoWidget->setStyleSheet("background-color: transparent;");player->setVideoOutput(videoWidget);videoWidget->show();// 加载视频文件（支持 MP4、AVI 等常见格式）player->setSource (QUrl::fromLocalFile("/Users/xiaolixi/Desktop/录屏2025-03-01 11.03.06.mov"));// 设置循环播放player->setLoops (-1);QPushButton* start = new QPushButton("start");// 设置视频水平居中qs->addWidget (videoWidget, 0, Qt::AlignHCenter); // 关键：对齐方式qs->addWidget (start);QObject::connect(start, SIGNAL(pressed()), this,  SLOT(playVideo()));
}MainWindow::~MainWindow()
{delete ui;
}

• h文件

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include <QMediaPlayer>QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACEclass MainWindow : public QMainWindow
{Q_OBJECTpublic:MainWindow(QWidget *parent = nullptr);~MainWindow();private slots:void playVideo();private:Ui::MainWindow *ui;QMediaPlayer *player;
};
#endif // MAINWINDOW_H

• pro文件

QT       += core gui
QT +=   multimediawidgets
QT +=   multimediagreaterThan(QT_MAJOR_VERSION, 4): QT += widgetsCONFIG += c++17# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0SOURCES += \main.cpp \mainwindow.cppHEADERS += \mainwindow.hFORMS += \mainwindow.ui# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

缺点

视频大小固定了。但是在我的场景中这个确定不影响。