[英]QT QLabel setPixmap from QAbstractVideoSurface
我正在實現自己的類,以在Windows下從QCamera探測視頻幀。 它是QAbstractVideoSurface的子類。 因此,我的探針生成了QPixmap,我試圖在QLabel上繪制(作為取景器)。 我在QLabel setPixmap調用上出現了分段錯誤。
我確定我的Qpixmap制作正確,因為我可以使用save()將其保存在磁盤上。 我的QLabel已初始化並且運行良好,因為我可以從磁盤加載QPixmap並將其設置為QLabel。 我猜有一個像素圖的格式有問題,但不知道如何糾正它:(
我的密碼
框架探針
#ifndef FRAMEPROBE_H
#define FRAMEPROBE_H
#include <QAbstractVideoSurface>
#include <QList>
#include <QPixmap>
class FrameProbe : public QAbstractVideoSurface
{
Q_OBJECT
public:
explicit FrameProbe(QObject *parent = 0);
QList<QVideoFrame::PixelFormat> supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const;
bool present(const QVideoFrame &frame);
signals:
void frameAvailable(QImage frame);
void frameReady(QPixmap frame);
public slots:
};
#endif // FRAMEPROBE_H
frameprobe.cpp
#include "frameprobe.h"
FrameProbe::FrameProbe(QObject *parent) :
QAbstractVideoSurface(parent)
{
}
QList<QVideoFrame::PixelFormat> FrameProbe::supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const
{
Q_UNUSED(handleType);
return QList<QVideoFrame::PixelFormat>()
<< QVideoFrame::Format_ARGB32
<< QVideoFrame::Format_ARGB32_Premultiplied
<< QVideoFrame::Format_RGB32
<< QVideoFrame::Format_RGB24
<< QVideoFrame::Format_RGB565
<< QVideoFrame::Format_RGB555
<< QVideoFrame::Format_ARGB8565_Premultiplied
<< QVideoFrame::Format_BGRA32
<< QVideoFrame::Format_BGRA32_Premultiplied
<< QVideoFrame::Format_BGR32
<< QVideoFrame::Format_BGR24
<< QVideoFrame::Format_BGR565
<< QVideoFrame::Format_BGR555
<< QVideoFrame::Format_BGRA5658_Premultiplied
<< QVideoFrame::Format_AYUV444
<< QVideoFrame::Format_AYUV444_Premultiplied
<< QVideoFrame::Format_YUV444
<< QVideoFrame::Format_YUV420P
<< QVideoFrame::Format_YV12
<< QVideoFrame::Format_UYVY
<< QVideoFrame::Format_YUYV
<< QVideoFrame::Format_NV12
<< QVideoFrame::Format_NV21
<< QVideoFrame::Format_IMC1
<< QVideoFrame::Format_IMC2
<< QVideoFrame::Format_IMC3
<< QVideoFrame::Format_IMC4
<< QVideoFrame::Format_Y8
<< QVideoFrame::Format_Y16
<< QVideoFrame::Format_Jpeg
<< QVideoFrame::Format_CameraRaw
<< QVideoFrame::Format_AdobeDng;
}
bool FrameProbe::present(const QVideoFrame &frame)
{
if (frame.isValid()) {
QVideoFrame cloneFrame(frame);
cloneFrame.map(QAbstractVideoBuffer::ReadOnly);
QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(cloneFrame.pixelFormat());
const QImage image(cloneFrame.bits(),
cloneFrame.width(),
cloneFrame.height(),
imageFormat);
emit frameAvailable(image);
emit frameReady(QPixmap::fromImage(image));
cloneFrame.unmap();
return true;
}
return false;
}
初始化代碼
QCamera * MyCamera= new QCamera(CameraDeviceName);
MyCamera->setCaptureMode( QCamera::CaptureVideo );
Label = new QLabel();
Label->setText("Label");
FrameProbe * VSurface = new FrameProbe();
MyCamera->setViewfinder(VSurface);
connect(VSurface, SIGNAL(frameAvailable(QImage)), this, SLOT(video_probed(QImage)));
connect(VSurface, SIGNAL(frameReady(QPixmap)), this,SLOT(video_forward(QPixmap)));
ui->gridLayout->addWidget(Label,0,0);
MyCamera->start();
和插槽
void MainWindow::video_probed(QImage InVideoFrame){
FramesProbed++;
std::cout<<FramesProbed<<std::endl;
}
void MainWindow::video_forward(QPixmap InVideoFrame){
Label->setPixmap(InVideoFrame); //<<<<<<<<< Segmentation Fault here
}
如果我將video_forward插槽更改為類似的內容
void MainWindow::video_forward(QPixmap InVideoFrame){
InVideoFrame.save("c:\\temp\\a.jpg",0,-1);
QPixmap a;
a.load("c:\\temp\\a.jpg");
Label->setPixmap(a);
}
這行得通。 當然很慢:)但可以工作...
PS:在FrameProbe :: present圖像中具有QImage :: Format_RGB32格式。
解:
bool FrameProbe::present(const QVideoFrame &frame)
{
...
emit frameAvailable(image.copy());
...
}
// slot video_probed
connect(VSurface, &FrameProbe::frameAvailable, [=](QImage a){
Label->setPixmap(QPixmap::fromImage(a));
});
那么為什么崩潰:
因為您正在使用以下構造QImage
:
QImage :: QImage(uchar *數據,整數寬度,整數高度,格式格式,QImageCleanupFunction cleanupFunction = Q_NULLPTR,無效* cleanupInfo = Q_NULLPTR)
第一個參數data
是從cloneFrame
設置的,它將在cloneFrame.unmap();
之后釋放cloneFrame.unmap();
。 data
在QLabel::paintEvent
堆棧中將不存在。
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