IplImage 与 QImage 相互转换

在使用Qt和OpenCV编程时，对于它们各自的图像类QImage和IplImage难以避免的需要互相之间的转换，下面我们就来看它们的相互转换。

1. QImage 转换为 IplImage

IplImage *QImageToIplImage(const QImage * qImage)
{
    int width = qImage->width();
    int height = qImage->height();
    CvSize Size;
    Size.height = height;
    Size.width = width;

    IplImage *charIplImageBuffer = cvCreateImage(Size, IPL_DEPTH_8U, 1);
    char *charTemp = (char *) charIplImageBuffer->imageData;

    for (int y = 0; y < height; y++)
    {
        for (int x = 0; x < width; x++)
        {
            int index = y * width + x;
            charTemp[index] = (char) qGray(qImage->pixel(x, y));
        }
    }
    return charIplImageBuffer;
}

2. IplImage 转换为 QImage

QImage *IplImageToQImage(const IplImage * iplImage)
{
    uchar *qImageBuffer = NULL;
    int width = iplImage->width;

    // Note here that OpenCV image is stored so that each lined is
    // 32-bits aligned thus * explaining the necessity to "skip"
    // the few last bytes of each line of OpenCV image buffer.
    int widthStep = iplImage->widthStep;
    int height = iplImage->height;

    switch (iplImage->depth)
    {
    case IPL_DEPTH_8U:
        if (iplImage->nChannels == 1)
        {
            // IplImage 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)
        {
            // IplImage 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)
        {
            // IplImage 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 *)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(uint16_t)-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)
        {
            // IplImage 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 = (*iplImagePtr++);

                    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;
    if (iplImage->nChannels == 1)
    {
        QVector<QRgb> colorTable;
        for (int i = 0; i < 256; i++)
        {
            colorTable.push_back(qRgb(i, i, i));
        }
        qImage = new QImage(qImageBuffer, width, height, QImage::Format_Indexed8);
        qImage->setColorTable(colorTable);
    }
    else
    {
        qImage = new QImage(qImageBuffer, width, height, QImage::Format_RGB32);
    }

    return qImage;
}

精简版：

QImage *IplImageToQImage(IplImage *image){
    QImage *result;
    if (image){
        uchar * qImageBuffer = NULL;
        int width = image->width;
        int widthStep = image->widthStep;
        int height = image->height;
        QImage::Format format = QImage::Format_Invalid;
        if (IPL_DEPTH_8U == image->depth && 3 == image->nChannels){
            qImageBuffer = (uchar *) malloc(width * height * 4 * sizeof(uchar));
            uchar *QImagePtr = qImageBuffer;
            const uchar *iplImagePtr = (const uchar *) image->imageData;
            format = QImage::Format_RGB32;
            if (!qImageBuffer){
                qDebug() << "Insufficient memory for image buffer!" << endl;
                return result;
            }
            for (int y = 0; y < height; y++)
            {
                for (int x = 0; x < width; x++)
                {
                    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("Image format is not supported: depth=%d and %d channels
", image->depth, image->nChannels);
            return result;
        }
        if (qImageBuffer){
            QImage *result = new QImage(qImageBuffer, image->width, image->height, format);
        }
    } else {
        qDebug() << "Image pointer is NULL" << endl;
    }
    return result;
}