[solved ] binary data to QTcpSocket

S.ANAND

Please help :'(

I am reading a image example a.jpg by
@
QFile file("d:/a.jpg");
file.open(QIODevice::ReadOnly);
QTextStream st(&file);
@
when you extract info like st.readlAll();

we get all the binary stuff like all unknow chars.

but
when i convert it to char * i.e ASCII by using ( st.readAll().toAscii() ) it is getting only 4 chars others are missing..
so can any please help me to convert entire QString i mean binary data of image to ASCII because the application i am working only supports ASCII please help.

I tried as many possible combinations as possible but not working . !http://img547.imageshack.us/img547/6366/16772393.png(Before convertion to ASCII)!

!http://img35.imageshack.us/img35/1824/39767045.png(After i convert to ASCII)!

I am attaching images .

SGaist

Hi,

Before digging deeper, why do you want/need to read a JPEG like this ?

S.ANAND

hi.

Actually i need to transfer jpeg image in a network using QtcpSocket so QTcpSocket::write() function only supports ascii or bytearray . that is the reason to convert to ASCII

SGaist

Then, why not simply use QFile's "readAll()":http://qt-project.org/doc/qt-4.8/qiodevice.html#readAll ? It returns you a QByteArray with the data from the file

S.ANAND

Hi

That is not working i am getting the same output the second image one.

mlong

Don't convert to ASCII. A char* is going to give you trouble the first time it encounters 0x00 (NULL) which will be interpreted as the end of the string. (JPEGs will certainly have a number of NULL characters in them -- I bet the first one you're encountering is at position 5 in your data.) A QByteArray will be sufficient to hold your data. You shouldn't be using a QTextStream at all, also. As SGaist said, QFile::readAll() should get you what you want. However, if you were insistent on using a stream, you'd need to use a QDataStream instead.

How, exactly, are you checking your data?

S.ANAND

Thats not working.

I am checking like this
@
QFile file("d:/a.jpg");
file.open(QIODevice::ReadOnly);
ui->textEdit->append(file.readAll());
file.close();
@
It is giving second image output.

edit: please use @ tags around code sections; Andre

ChrisW67

Well of course it does. You need to realise that a JPEG file's content is not text and therefore any attempt to treat it is as such (e.g. with QTextStream or QTextEdit, notice the word Text) is doomed to fail. A JPEG binary file will typically have a zero in its fifth byte so you will generally get only four potential characters (byte FF D8 FF E0 in hex) before the string is considered ended. If byte 5 is not zero then the 11th byte will always be zero and you may see a recognisable "JFIF" in the text.

Why don't you take a step back and explain the result you are expecting to achieve.

Code_ReaQtor

As ChrisW67 said, JPEG is NOT a text file so QTextEdit won't be able to support it. If you want to show it as text, at least convert it using QByteArray::toHex(). But I don't think we are on the right track then.

S.ANAND

@ QFile file("d:/a.jpg");

file.open(QIODevice::ReadOnly&#41;;

this->sock = new QTcpSocket;

connect(this->sock,SIGNAL(bytesWritten(qint64)),this,SLOT(q(qint64)));
connect(sock,SIGNAL(connected()),this,SLOT(con()));
connect(sock,SIGNAL(disconnected()),this,SLOT(dis()));

this->sock->connectToHost("192.168.1.2",8080);

this->sock->waitForConnected();

sock->write(file.readAll().data());
sock->waitForBytesWritten(-1);

sock->close();

file.close();
@
This is my code i need to send the image via network using QTcpSocket but the method QTcpSocket::write() will only support char * or bytearray but even if i convert the above image from QString to QByteArry and pass to QTcpSocket and send it is only showing 4 characters in the both cases QByteArray and char *.

Edit: again, use @ tags around code sections please; Andre

SGaist

Don't convert anything, just send the byte array created by readAll().

Besides, write(file.readAll().data()) is a bad idea. data() will return a pointer to the data from a temporary QByteArray created by file.readAll(). You don't really know when that byte array will be destroyed.

If you want to show the image on the other end, use a "QImage":http://qt-project.org/doc/qt-4.8/qimage.html + "QLabel":http://qt-project.org/doc/qt-4.8/qlabel.html combo

And please enclose your code with code tags so that it's cleaner to read.

Code_ReaQtor

[quote author="S.ANAND" date="1363174874"] QTcpSocket::write() will only support char * or bytearray but even if i convert the above image from QString to QByteArry and pass to QTcpSocket and send it is only showing 4 characters in the both cases QByteArray and char *. [/quote]

It should work... The fact that you are using QTextEdit is NOT correct. QTextEdit only support "Texts".

S.ANAND

Ha that's done the trick.
using file.readAll() instead of file.readAll().data()

Thank You SGaist and all others you replied. :)

S.ANAND

Yes that is also the mistake i made Code_ReaQtor Thank you .

SGaist

You're welcome

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