[Qt-interest] Creating QPixmap from QByteArray causes segfault [SOLVED]

[Mandeep Sandhu]

On Wed, May 5, 2010 at 1:00 AM, Malyushytsky, Alex <alex at wai.com> wrote:
>>> Is there a way I can instantiate QPixmap's in a non-GUI app?
>
> You can use QImage instead. It does not require GUI.

I could. But I'm writing a helper/util class which will be used in a
GUI app. So in the actual app there won;t be an issue, it's just that
when I want to test it out...I don;t want to write a GUI app!!! :)

Thanks,
-mandeep

>
> Alex
>
> -----Original Message-----
> From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of Mandeep Sandhu
> Sent: Monday, May 03, 2010 9:56 PM
> To: qt-interest at trolltech.com
> Subject: Re: [Qt-interest] Creating QPixmap from QByteArray causes segfault [SOLVED]
>
> This error was coming because I was trying to use a QPixmap in a
> console (non-GUI) application.
>
> It works fine if I use it in a GUI app.
>
> I'm actually writing a helper class, which was supposed to download an
> image along with some other metatdata and emit this result.
>
> For testing this class I thought I'd make a simple console app and see
> if it works. I did not want to go the GUI way since there really isn't
> any GUI part to test.
>
> Is there a way I can instantiate QPixmap's in a non-GUI app?
>
> Thanks,
> -mandeep
>
> On Mon, May 3, 2010 at 1:52 PM, Mandeep Sandhu
> <mandeepsandhu.chd at gmail.com> wrote:
>> Hi All,
>>
>> I'm trying to create a QPixmap from image data received from the
>> network. I have connected the QNAM's finshed signal to my slot, which
>> reads the data stream from the reply object (after all necessary error
>> checks) and tries creating a QPixmap object using the loadFromData()
>> API. However, this does not work and causes a seg fault! If I convert
>> the byte array to a const char* then it doesn't seg fault but gives
>> out the following error:
>>
>> Corrupt JPEG data: 1 extraneous bytes before marker 0xd9
>> JPEG datastream contains no image
>>
>> The reply->bytesAvailable() shown in the finished signal exactly
>> correspond to the number of bytes of the image. The image is not
>> corrupt as I can see it eog/gqview/display progs w/o any error.
>>
>> Here's the snippet that converts the data to image:
>>
>> void getData(QNetworkReply* reply) {
>>    qDebug() << "Status code"
>>             <<
>> reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
>>
>>    if (reply->error() != QNetworkReply::NoError) {
>>        qDebug() << "Error fetching data from" << reply->url();
>>        return;
>>    }
>>
>>    qDebug() << "Bytes available" << reply->bytesAvailable();
>>    if (reply->bytesAvailable() == 0) {
>>        return;
>>    }
>>
>>    QByteArray bytes = reply->readAll();
>>    qDebug() << "Rx'ed" << bytes.size();
>>
>>    QPixmap pixi;
>>    pixi.loadFromData(bytes.data());
>>
>>    reply->deleteLater();
>> }
>>
>> I'm sure ppl have done this before and got it working.
>>
>> Any clues as to what could be going wrong?
>>
>> Thanks,
>> -mandeep
>>
>
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