QT下对OpenCV抓取图片的显示

1.背景

Opencv中通过摄像头捕捉到的每帧图像的数据结构是IplImage类型的，要把它显示到Qt窗口中就需要把它转化为QImage类型的图像。

2.代码

#include <QVector>#include <cstring>QImage MyThread::IplImageToQImage(const IplImage * iplImage,double mini, double maxi){    uchar *qImageBuffer = NULL;        int width = iplImage->width;/* Note here that OpenCV image is stored so that each lined is32-bits aligned thus* explaining the necessity to "skip" the few last bytes of eachline of OpenCV image buffer.*/        int widthStep = iplImage->widthStep;        int height = iplImage->height;        switch (iplImage->depth)        {            case IPL_DEPTH_8U:            if(iplImage->nChannels == 1)            {            /* OpenCV image is stored with one byte grey pixel. We convert it            to an 8 bit depth QImage.            */                   qImageBuffer = (uchar *) malloc(width*height*sizeof(uchar));                uchar *QImagePtr = qImageBuffer;                const uchar *iplImagePtr = (const uchar *) iplImage->imageData;                   for(int y = 0; y < height; y++)                {                    // Copy line by line                        memcpy(QImagePtr, iplImagePtr, width);                        QImagePtr += width;                        iplImagePtr += widthStep;                }               }            else if(iplImage->nChannels == 3)            {                    /* OpenCV image is stored with 3 byte color pixels (3 channels).                    We convert it to a 32 bit depth QImage.                    */                    qImageBuffer = (uchar *) malloc(width*height*4*sizeof(uchar));                    uchar *QImagePtr = qImageBuffer;                    const uchar *iplImagePtr = (const uchar *) iplImage->imageData;                    for(int y = 0; y < height; y++)                    {                        for (int x = 0; x < width; x++)                        {                                // We cannot help but copy manually.                                QImagePtr[0] = iplImagePtr[0];                                QImagePtr[1] = iplImagePtr[1];                                QImagePtr[2] = iplImagePtr[2];                                QImagePtr[3] = 0;                                       QImagePtr += 4;                                iplImagePtr += 3;                        }                        iplImagePtr += widthStep-3*width;                    }                   }            else            {                    qDebug("IplImageToQImage: image format is not supported : depth=8U and %d channels ", iplImage->nChannels);            }            break;            case IPL_DEPTH_16U:            if(iplImage->nChannels == 1)            {            /* OpenCV image is stored with 2 bytes grey pixel. We convert it            to an 8 bit depth QImage.            */                    qImageBuffer = (uchar *) malloc(width*height*sizeof(uchar));                    uchar *QImagePtr = qImageBuffer;                    //const uint16_t *iplImagePtr = (const uint16_t *);            const unsigned int *iplImagePtr = (const unsigned int *)iplImage->imageData;                    for (int y = 0; y < height; y++)                    {                        for (int x = 0; x < width; x++)                        {                        // We take only the highest part of the 16 bit value. It is                        //similar to dividing by 256.                            *QImagePtr++ = ((*iplImagePtr++) >> 8);                        }                        iplImagePtr += widthStep/sizeof(unsigned int)-width;                    }            }            else            {                    qDebug("IplImageToQImage: image format is not supported : depth=16U and %d channels ", iplImage->nChannels);               }            break;            case IPL_DEPTH_32F:             if(iplImage->nChannels == 1)             {            /* OpenCV image is stored with float (4 bytes) grey pixel. We            convert it to an 8 bit depth QImage.            */                     qImageBuffer = (uchar *) malloc(width*height*sizeof(uchar));                     uchar *QImagePtr = qImageBuffer;                     const float *iplImagePtr = (const float *) iplImage->imageData;                     for(int y = 0; y < height; y++)                     {                         for(int x = 0; x < width; x++)                         {                                 uchar p;                                 float pf = 255 * ((*iplImagePtr++) - mini) / (maxi - mini);                                 if(pf < 0) p = 0;                                 else if(pf > 255) p = 255;                                 else p = (uchar) pf;                                    *QImagePtr++ = p;                          }                         iplImagePtr += widthStep/sizeof(float)-width;                     }             }             else             {                     qDebug("IplImageToQImage: image format is not supported : depth=32F and %d channels ", iplImage->nChannels);             }                   break;               case IPL_DEPTH_64F:             if(iplImage->nChannels == 1)             {                /* OpenCV image is stored with double (8 bytes) grey pixel. We                convert it to an 8 bit depth QImage.                */                    qImageBuffer = (uchar *) malloc(width*height*sizeof(uchar));                    uchar *QImagePtr = qImageBuffer;                    const double *iplImagePtr = (const double *) iplImage->imageData;                    for(int y = 0; y < height; y++)                    {                        for(int x = 0; x < width; x++)                        {                                uchar p;                                double pf = 255 * ((*iplImagePtr++) - mini) / (maxi - mini);                                   if(pf < 0) p = 0;                                else if(pf > 255) p = 255;                                else p = (uchar) pf;                                   *QImagePtr++ = p;                        }                        iplImagePtr += widthStep/sizeof(double)-width;                    }            }            else            {                    qDebug("IplImageToQImage: image format is not supported : depth=64F and %d channels ", iplImage->nChannels);            }            break;            default:                qDebug("IplImageToQImage: image format is not supported : depth=%d and %d channels ", iplImage->depth, iplImage->nChannels);        }        QImage qImage;        QVector<QRgb> vcolorTable;        if(iplImage->nChannels == 1)        {            // We should check who is going to destroy this allocation.            QRgb *colorTable = new QRgb[256];            for(int i = 0; i < 256; i++)            {                   colorTable[i] = qRgb(i, i, i);                   vcolorTable[i] = colorTable[i];            }            qImage = QImage(qImageBuffer, width, height, QImage::Format_Indexed8).copy();            qImage.setColorTable(vcolorTable);        }        else        {            qImage = QImage(qImageBuffer, width, height, QImage::Format_RGB32).copy();        }    free(qImageBuffer);    return qImage;}

上面完成的格式转换，接下来进行显示

摄像头获取每一帧IplImage*类型的图像，转化为QImage类型的图像，用update()发出一个paintEvent(QPaintEvent*)事件，如此不断更新图像。(IplImageToQImage中的mini和maxi默认初始化为0)

void ImageViewer::paintEvent(QPaintEvent *){    QPainter painter(this);    painter.drawImage(QPoint(0,0), *image);}bool ImageViewer::ShowImage(){    IplImage *pImage = NULL;    CvCapture *pCapture = NULL;    if((pCapture = cvCaptureFromCAM(-1)) == NULL){        cout << "Open camera failed! ";        return false;    }    while((pImage = cvQueryFrame(pCapture)) != NULL){        image = IplImageToQImage(pImage);        update();    }    cvReleaseImage(&pImage);    cvReleaseCapture(&pCapture);    return true;}