Qt实战：如何打开摄像头并达成视频的实时预览

文章目录

• • 一、在 pro 文件中添加模块
  • 二、代码实现

一、在 pro 文件中添加模块

在 Qt5 中，如果你要使用 QCamera、QCameraViewfinder、QCameraImageCapture 等类，需要在 pro 文件里添加 multimedia 模块。

QT += multimedia multimediawidgets

• multimedia：核心多媒体功能（QCamera、QCameraImageCapture）
• multimediawidgets：视频显示控件（QCameraViewfinder、QVideoWidget）

检查包含头文件：

#include <QCamera>
  #include <QCameraViewfinder>
    #include <QCameraImageCapture>

二、代码实现

在 Qt5 里，使用的是 QCamera + QCameraViewfinder + QCameraImageCapture。

CameraWindow.h

#pragma once
#include <QWidget>
  #include <QCamera>
    #include <QCameraViewfinder>
      #include <QCameraImageCapture>
        #include <QPushButton>
          #include <QVBoxLayout>
            #include <QLabel>
              class CameraWindow
              : public QWidget
              {
              Q_OBJECT
              public:
              explicit CameraWindow(QWidget *parent = nullptr);
              private slots:
              void onOpenCamera();
              void onCaptureImage();
              void onCloseCamera();
              void onImageCaptured(int id, const QImage &preview);
              private:
              QCamera *m_camera = nullptr;
              QCameraViewfinder *m_viewfinder = nullptr;
              QCameraImageCapture *m_imageCapture = nullptr;
              QPushButton *m_btnOpen;
              QPushButton *m_btnCapture;
              QPushButton *m_btnClose;
              QLabel *m_labelPhoto;
              };

CameraWindow.cpp

#include "CameraWindow.h"
#include <QDebug>
  #include <QDateTime>
    CameraWindow::CameraWindow(QWidget *parent) : QWidget(parent)
    {
    setWindowTitle("Qt5 摄像头示例");
    resize(800, 600);
    // 预览控件
    m_viewfinder = new QCameraViewfinder(this);
    m_viewfinder->
    setMinimumSize(640, 480);
    // 按钮
    m_btnOpen = new QPushButton("打开摄像头");
    m_btnCapture = new QPushButton("拍照");
    m_btnClose = new QPushButton("关闭摄像头");
    // 拍照结果显示
    m_labelPhoto = new QLabel;
    m_labelPhoto->
    setFixedSize(200, 150);
    m_labelPhoto->
    setStyleSheet("border: 1px solid gray;");
    // 布局
    auto vLayout = new QVBoxLayout(this);
    vLayout->
    addWidget(m_viewfinder, 1);
    auto hLayout = new QHBoxLayout;
    hLayout->
    addWidget(m_btnOpen);
    hLayout->
    addWidget(m_btnCapture);
    hLayout->
    addWidget(m_btnClose);
    hLayout->
    addWidget(m_labelPhoto);
    vLayout->
    addLayout(hLayout);
    // 信号槽
    connect(m_btnOpen, &QPushButton::clicked, this, &CameraWindow::onOpenCamera);
    connect(m_btnCapture, &QPushButton::clicked, this, &CameraWindow::onCaptureImage);
    connect(m_btnClose, &QPushButton::clicked, this, &CameraWindow::onCloseCamera);
    }
    void CameraWindow::onOpenCamera()
    {
    if (m_camera) return;
    // 已经打开
    m_camera = new QCamera(this);
    m_camera->
    setViewfinder(m_viewfinder);
    m_imageCapture = new QCameraImageCapture(m_camera, this);
    connect(m_imageCapture, &QCameraImageCapture::imageCaptured,
    this, &CameraWindow::onImageCaptured);
    m_camera->
    start();
    qDebug() <<
    "摄像头已打开";
    }
    void CameraWindow::onCaptureImage()
    {
    if (!m_imageCapture) return;
    QString filename = QString("photo_%1.jpg")
    .arg(QDateTime::currentDateTime().toString("yyyyMMdd_hhmmss"));
    m_imageCapture->
    capture(filename);
    qDebug() <<
    "已拍照保存到:" << filename;
    }
    void CameraWindow::onCloseCamera()
    {
    if (m_camera) {
    m_camera->
    stop();
    delete m_camera;
    m_camera = nullptr;
    delete m_imageCapture;
    m_imageCapture = nullptr;
    qDebug() <<
    "摄像头已关闭";
    }
    }
    void CameraWindow::onImageCaptured(int, const QImage &preview)
    {
    m_labelPhoto->
    setPixmap(QPixmap::fromImage(preview).scaled(m_labelPhoto->
    size(),
    Qt::KeepAspectRatio,
    Qt::SmoothTransformation));
    }

main.cpp

#include "CameraWindow.h"
#include <QApplication>
  int main(int argc, char *argv[])
  {
  QApplication a(argc, argv);
  CameraWindow w;
  w.show();
  return a.exec();
  }