Convert IplImage to QByteArray

soroush

Hello

I need to send IplImages fetched from camera with UDP socket. I'm using Qt. The application has two parts. The server should fetch images from digital camera and send them to a specific port via upd (broadcasting). Clients are gui applications. they will receive images and display them on a QLabel.

I'm using openCV for images, so my input of camera is an IplImage. I know how to convert it to QImage/QPixmap and display it on a label. But can't find a way to send IplImage through a udp socket... QUdpSocet::writeDatagram only accepts QByteArray so I neet to convert IplImage to QByteArray and this should be very fast (It's not appropriate to convert images on server).

qxoz

Try this
@QByteArray bArray;
QBuffer buff(&bArray);
QImage img_Tasvir;
img_Tasvir.save(&buff,"PNG");@

soroush

[quote author="qxoz" date="1322728572"]Try this
@QByteArray bArray;
QBuffer buff(&bArray);
QImage img_Tasvir;
img_Tasvir.save(&buff,"PNG");@[/quote]

I don't want to convert IpliImage to QImage on the server side. It's too time-consuming. It should process at least 20 frames per second on a 1GHz Vortex86XD...

soroush

Ok I tried this:
@
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QUdpSocket socket;
quint16 port = atoi(argv[1]);
cout << "Connecting to UDP socket..." << endl;
cout << "Detecting Digital Camera..." << endl;
CvCapture * camera = cvCreateCameraCapture(0);
assert(camera);
cout << "Image transmition started..." << endl;
cout << "Press Ctrl+C to end program" << endl;
cout << port << endl;
while(true)
{
IplImage * image=cvQueryFrame(camera);
assert(image);
cvResize(image,image,2);
QByteArray array(image->imageData);
cout<<"size: " << array.size() << endl;
if(socket.writeDatagram(array,QHostAddress::Broadcast,port)==-1)
{
cout<<socket.errorString().toAscii().data() << endl;
exit(0);
}
}
return a.exec();
}
@
There output is:
@
size: 348789
Datagram was too large to send
@

goetz

Two errors here:

First:

@
QByteArray(image->imageData);
@

is likely to truncate your data, as it stops at the first null byte.

change it to

@
QByteArray(image->imageData, image->imageSize);
@

Second:
An UDP datagram can only contain 8192 bytes, but you discovered that already in that "other thread":/forums/viewthread/12127/.

soroush

bq. 1
QByteArray(image->imageData);
is likely to truncate your data, as it stops at the first null byte.
change it to

Yes, i noticed about that. forgot to correct above code :)

bq. An UDP datagram can only contain 8192 bytes, but you discovered that already in that other thread.

Although with TCP I have no chance to send 30 fps video by individual images on LAN Ethernet cable... I found that sending Images is not a good idea. It should be an AVI stream with compression.

Thanks

randyclark

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