Qt--windows平台上如何获取qml中Camera的数据

柔情只为你懂 2022-09-26 03:52 14阅读 0赞

曾经写了一个博客：  
[我们为什么不习惯使用qml？][qml] 最后有一个悬念，到底如何在C++代码中获取qml中camera的数据呢？

**QAbstractVideoFilter**  
The QAbstractVideoFilter class represents a filter that is applied to the video frames received by a VideoOutput type.  
[https://doc-snapshots.qt.io/qt5-dev/qabstractvideofilter.html\#details][https_doc-snapshots.qt.io_qt5-dev_qabstractvideofilter.html_details]

**QVideoFilterRunnable**  
The QVideoFilterRunnable class represents the implementation of a filter that owns all graphics and computational resources, and performs the actual filtering or calculations.

上面两个类自己去看官方文档吧，翻译不好。

开始撸代码!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

写一个自己的类叫**CameraFilter**吧：

camerafilter.h

#ifndef CAMERAFILTER
    #define CAMERAFILTER
    #include <QVideoFilterRunnable>
    
    class CameraFilter : public QAbstractVideoFilter
    {
        Q_OBJECT
    public:
        CameraFilter();
        ~CameraFilter();
        QVideoFilterRunnable *createFilterRunnable();
    private:
    signals:
        void finished(QObject *result);
        void cameraFrameSignal(QVideoFrame);
    public slots:
    
    };
    
    class CameraFilterRunnable : public QVideoFilterRunnable
    {
    public:
        CameraFilterRunnable(CameraFilter* filter = NULL);
        ~CameraFilterRunnable();
        QVideoFrame run(QVideoFrame *input, const QVideoSurfaceFormat &surfaceFormat, RunFlags flags);
    
    private:
        CameraFilter *m_filter;
    };
    
    #endif // CAMERAFILTER

camerafilter.cc

#include "camerafilter.h"
    #include "qdebug.h"
    
    CameraFilter::CameraFilter()
    {
    
    }
    
    CameraFilter::~CameraFilter()
    {
    
    }
    
    QVideoFilterRunnable *CameraFilter::createFilterRunnable()
    {
        return new CameraFilterRunnable(this);
    }
    
    CameraFilterRunnable::CameraFilterRunnable(CameraFilter* filter)
    {
        m_filter = filter;
    }
    
    CameraFilterRunnable::~CameraFilterRunnable()
    {
    
    }
    
    QVideoFrame CameraFilterRunnable::run(QVideoFrame *input, const QVideoSurfaceFormat &surfaceFormat, RunFlags flags)
    {
        QVideoFrame cloneFrame(*input);
    
        emit m_filter->cameraFrameSignal(cloneFrame);
    
        return cloneFrame;
    }

不要骂娘，上面的代码很简单的，其实官方的文档中也有类似的代码片段，不懂的自己看奥。  
是通过：

emit m_filter->cameraFrameSignal(cloneFrame);

我们自己写一个slot，然后对Frame进行相应的处理！

接下来才是高潮！！！！

**第一步、让qml中理解我们自己的类CameraFilter(Defining QML Types from C++) ：**

在C++中注册：

qmlRegisterType<CameraFilter>("CameraFilter", 1, 0, "CameraFilter");

在qml中导入：

import CameraFilter 1.0

**第二步、在qml中干点大事儿：**

Camera { objectName: "CameraObject" id: camera imageProcessing.whiteBalanceMode: CameraImageProcessing.WhiteBalanceFlash exposure { exposureCompensation: -1.0 exposureMode: Camera.ExposurePortrait }
                    captureMode: Camera.CaptureVideo
                    flash.mode: Camera.FlashRedEyeReduction
                }
    
                VideoOutput { width: 160 height: 90 id: video_output objectName: "VidelOutputObject" source: camera anchors.fill: parent focus : visible // to receive focus and capture key events when visible visible: false filters: [filter] fillMode: VideoOutput.PreserveAspectFit }
    
                CameraFilter { objectName: "cameraFilterObject" id: filter }

[qml]: http://blog.csdn.net/wangshubo1989/article/details/52029185
[https_doc-snapshots.qt.io_qt5-dev_qabstractvideofilter.html_details]: https://doc-snapshots.qt.io/qt5-dev/qabstractvideofilter.html#details