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demo中主要涉及的Qt类有：相机类QCamera，取景器类QCameraViewfinder，图像捕获类QCameraImageCapture，因此添加模块multimedia multimediawidgets。
QT += core gui multimedia multimediawidgets在widget.h中添加相关类声明：
class QCamera;class QCameraViewfinder;class QCameraImageCapture;class QCameraInfo;class QCameraViewfinderSettings;在类Widget中添加私有变量：
QCamera *camera; //相机QCameraViewfinder *viewfinder; //取景器QCameraImageCapture *imageCapture; //图像捕获QList<QCameraInfo> cameras; //相机列表QList<QSize> mResSize = {}; //分辨率列表在widget.cpp中添加头文件：
#include <QCamera>#include <QCameraInfo>#include <QCameraViewfinder>#include <QCameraImageCapture>#include <QFileDialog>#include <QList>#include <QDebug>在widget.cpp的构造函数中添加代码：
先设置下窗口名称及大小
setWindowTitle("Camera");setFixedSize(600,400);接着获取所有相机列表并选择一个相机初始化
cameras = QCameraInfo::availableCameras(); //获取所有相机的列表//qDebug() << "this is camera: ";if (cameras.count() > 0) { for(const QCameraInfo &cameraInfo:cameras) { qDebug() << cameraInfo.description(); } camera = new QCamera(cameras.at(0)); //初始化实例化一个相机对象}实例化取景器类，取景器本质是一个窗口类，若不将当前窗口设为父对象，则可以另起一个窗口显示。将当前窗口设为父对象后，视频画面便在当前窗口显示。
//设置取景器viewfinder = new QCameraViewfinder(this);camera->setViewfinder(viewfinder);viewfinder->resize(600,350); //设置取景器显示大小//viewfinder->show();实例化一个图像捕获类，并开启相机
imageCapture = new QCameraImageCapture(camera);camera->start(); //开启相机设置默认摄像头的分辨率及帧率。注意：帧率一定要与摄像头匹配，否则不会显示画面。
//设置默认摄像头参数QCameraViewfinderSettings set;set.setResolution(640, 480); //设置显示分辨率set.setMaximumFrameRate(25); //设置帧率camera->setViewfinderSettings(set);设置两个下拉框部件的初始化
//添加初始化的相机选项for(const QCameraInfo &cameraInfo:cameras) { qDebug() << "CameraInfo:" << cameraInfo; ui->cameraSel->addItem(cameraInfo.description());}ui->cameraSel->setCurrentIndex(0);//添加初始化相机的分辨率选项mResSize = camera->supportedViewfinderResolutions();//qDebug() << "mResSize = " << mResSize;for (const QSize &msize:mResSize) { qDebug() << msize; //摄像头支持分辨率打印 ui->resolutionSel->addItem(QString::number(msize.width(), 10) + "*" + QString::number(msize.height(), 10));}ui->resolutionSel->setCurrentIndex(0);调整下widget.ui的内容，添加两个下拉框及一个按钮
编写信号槽连接
首先是选择摄影机，先释放之前的内存，再将camera指向新的。选择新的相机意味着分辨率选项也会变化，因此需要删除分辨率下拉框中前相机的所有分辨率选项，再添加新相机的所有分辨率选项。
connect(ui->cameraSel, QOverload<int>::of(&QComboBox::activated), [=](int index){ //qDebug() << "Index" << ui->cameraSel->currentIndex() << ": " << ui->cameraSel->currentText(); camera->stop(); delete camera; camera = new QCamera(cameras[index]); //camera指向指定的摄像头 camera->setCaptureMode(QCamera::CaptureStillImage); //设定捕获模式 camera->setViewfinder(viewfinder); //设置取景器 camera->start(); //删除前相机的所有分辨率内容 for (int i = 0; i < mResSize.size(); i++) { ui->resolutionSel->removeItem(0); } //添加新相机的所有分辨率 mResSize.clear(); //qDebug() << "now mResSize = " << mResSize; mResSize = camera->supportedViewfinderResolutions(); for (const QSize &msize:mResSize) { qDebug() << msize; //摄像头支持分辨率打印 ui->resolutionSel->addItem(QString::number(msize.width(), 10) + "*" + QString::number(msize.height(), 10)); } ui->resolutionSel->setCurrentIndex(0);});选择分辨率
connect(ui->resolutionSel, QOverload<int>::of(&QComboBox::activated), [=](int index){ //qDebug() << "Index" << ui->resolutionSel->currentIndex() << ": " << ui->resolutionSel->currentText(); //qDebug() << "mResSize:" << mResSize[index]; //重新设置摄像头参数 QCameraViewfinderSettings reset; reset.setResolution(mResSize[index]); camera->setViewfinderSettings(reset);});截图按钮
connect(ui->screenShot, &QPushButton::clicked, [=](){ camera->setCaptureMode(QCamera::CaptureStillImage); delete imageCapture; imageCapture = new QCameraImageCapture(camera); QString fileName = QFileDialog::getSaveFileName(); camera->searchAndLock(); imageCapture->capture(fileName); camera->unlock();});附完整代码
widget.h
#ifndef WIDGET_H#define WIDGET_H#include <QWidget>QT_BEGIN_NAMESPACEnamespace Ui { class Widget; }QT_END_NAMESPACEclass QCamera;class QCameraViewfinder;class QCameraImageCapture;class QCameraInfo;class QCameraViewfinderSettings;class Widget : public QWidget{ Q_OBJECTpublic: Widget(QWidget *parent = nullptr); ~Widget();private: Ui::Widget *ui; QCamera *camera; //相机 QCameraViewfinder *viewfinder; //取景器 QCameraImageCapture *imageCapture; //图像捕获 QList<QCameraInfo> cameras; //相机列表 QList<QSize> mResSize = {}; //分辨率列表 //QCameraViewfinderSettings *set;};#endif // WIDGET_Hwidget.cpp
#include "widget.h"#include "ui_widget.h"#include <QCamera>#include <QCameraInfo>#include <QCameraViewfinder>#include <QCameraImageCapture>#include <QFileDialog>#include <QList>#include <QDebug>Widget::Widget(QWidget *parent) : QWidget(parent) , ui(new Ui::Widget){ ui->setupUi(this); setWindowTitle("Camera"); setFixedSize(600,400); cameras = QCameraInfo::availableCameras(); //获取所有相机的列表 //qDebug() << "this is camera: "; if (cameras.count() > 0) { for(const QCameraInfo &cameraInfo:cameras) { qDebug() << cameraInfo.description(); } camera = new QCamera(cameras.at(0)); //初始化实例化一个相机对象 } //设置取景器 viewfinder = new QCameraViewfinder(this); camera->setViewfinder(viewfinder); viewfinder->resize(600,350); //设置取景器显示大小 //viewfinder->show(); imageCapture = new QCameraImageCapture(camera); camera->start(); //开启相机 //设置默认摄像头参数 QCameraViewfinderSettings set; set.setResolution(640, 480); //设置显示分辨率 set.setMaximumFrameRate(25); //设置帧率 camera->setViewfinderSettings(set); //添加初始化的相机选项 for(const QCameraInfo &cameraInfo:cameras) { qDebug() << "CameraInfo:" << cameraInfo; ui->cameraSel->addItem(cameraInfo.description()); } ui->cameraSel->setCurrentIndex(0); //添加初始化相机的分辨率选项 mResSize = camera->supportedViewfinderResolutions(); //qDebug() << "mResSize = " << mResSize; for (const QSize &msize:mResSize) { qDebug() << msize; //摄像头支持分辨率打印 ui->resolutionSel->addItem(QString::number(msize.width(), 10) + "*" + QString::number(msize.height(), 10)); } ui->resolutionSel->setCurrentIndex(0); //信号槽连接 connect(ui->cameraSel, QOverload<int>::of(&QComboBox::activated), [=](int index){ //qDebug() << "Index" << ui->cameraSel->currentIndex() << ": " << ui->cameraSel->currentText(); camera->stop(); delete camera; camera = new QCamera(cameras[index]); //camera指向指定的摄像头 camera->setCaptureMode(QCamera::CaptureStillImage); //设定捕获模式 camera->setViewfinder(viewfinder); //设置取景器 camera->start(); //删除前相机的所有分辨率内容 for (int i = 0; i < mResSize.size(); i++) { ui->resolutionSel->removeItem(0); } //添加新相机的所有分辨率 mResSize.clear(); //qDebug() << "now mResSize = " << mResSize; mResSize = camera->supportedViewfinderResolutions(); for (const QSize &msize:mResSize) { qDebug() << msize; //摄像头支持分辨率打印 ui->resolutionSel->addItem(QString::number(msize.width(), 10) + "*" + QString::number(msize.height(), 10)); } ui->resolutionSel->setCurrentIndex(0); }); connect(ui->resolutionSel, QOverload<int>::of(&QComboBox::activated), [=](int index){ //qDebug() << "Index" << ui->resolutionSel->currentIndex() << ": " << ui->resolutionSel->currentText(); //qDebug() << "mResSize:" << mResSize[index]; //重新设置摄像头参数 QCameraViewfinderSettings reset; reset.setResolution(mResSize[index]); camera->setViewfinderSettings(reset); }); connect(ui->screenShot, &QPushButton::clicked, [=](){ camera->setCaptureMode(QCamera::CaptureStillImage); delete imageCapture; imageCapture = new QCameraImageCapture(camera); QString fileName = QFileDialog::getSaveFileName(); camera->searchAndLock(); imageCapture->capture(fileName); camera->unlock(); });}Widget::~Widget(){ delete ui;}关于“Qt怎么使用QCamera实现切换相机,分辨率和图像捕获功能”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识，可以关注编程网行业资讯频道，小编每天都会为大家更新不同的知识点。
