Fastest method to convert IplImage IPL_DEPTH_32S to QImage Format_RGB32

Question

What is the fastest method to convert IplImage IPL_DEPTH_32S to QImage Format_RGB32?

I need to catch pictures from cam and show it on form with frequency 30 frames in se

Answer 1

Time ago I found some examples in the internet of how to do that. I improved the examples a bit for how to copy the images in a more easy way. Qt works normally only with char pixels (other image formats are normally called HDR images). I was wondering how you get a video buffer of 32 bit rgb in opencv... I have never seen that !

If you have a color image in opencv you could use this function to allocate memory:

QImage* allocateqtimagefromcv(IplImage* cvimg)
    {
        //if (cvimg->nChannels==1)
        //  {
        //  return new QImage(cvimg->width,cvimg->height,QImage::Format_Indexed8);
        //  }
        if (cvimg)
            {
            return new QImage(cvimg->width,cvimg->height,QImage::Format_ARGB32);
            }
    }

to just copy the IplImage to the qt image you could go the easy way and use this function:

void  IplImage2QImage(IplImage *iplImg,QImage* qimg)
{

char *data = iplImg->imageData;
    int channels = iplImg->nChannels;
int h = iplImg->height;
int w = iplImg->width;
for (int y = 0; y < h; y++, data += iplImg->widthStep)
{
for (int x = 0; x < w; x++)
{
char r, g, b, a = 0;
if (channels == 1)
{
r = data[x * channels];
g = data[x * channels];
b = data[x * channels];
}
else if (channels == 3)
{
r = data[x * channels + 2];
g = data[x * channels + 1];
b = data[x * channels];
}

if (channels == 4)
{
a = data[x * channels + 3];
qimg->setPixel(x, y, qRgba(r, g, b, a));
}

}
}


}

the following function could be a quicker solution:

static QImage IplImage2QImage(const IplImage *iplImage)
{
  int height = iplImage->height;
  int width = iplImage->width;
  if (iplImage->depth == IPL_DEPTH_8U && iplImage->nChannels == 3)
  {
      const uchar *qImageBuffer =(const uchar*)iplImage->imageData;
      QImage img(qImageBuffer, width, height, QImage::Format_RGB888);
      return img.rgbSwapped();
  }else{
    //qWarning() << "Image cannot be converted.";
   return QImage();
  }
} 

hope my function helped. Maybe someone know better ways of doing that :)