Qt5.14.2中使用QCamera实现切换相机、分辨率和图像捕获功能
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 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();
});
最终效果
附完整代码
widget.h
#ifndef WIDGET_H
#define WIDGET_H
#include widget.cpp
#include "widget.h"
#include "ui_widget.h"
#include