Can not convert A QByteArray to QImage on windows7

Neether

QT version 5.13.2

I read a image file from server,and cast into QImage

QByteArray filebyte = pReply->readAll();
QImage current_image = QImage::fromData(filebyte);

It's run success on windows10 and 11
but on windows7,I get an empty QImage
I just output the QByteArray into a file,and this file can normally opened as a image

And I trid to use QImageReader to figure out what happened

 QImageReader reader(filebyte);
 MTLOG_INFO << QStringLiteral("Image conversion failed. Error::%1").arg(reader.errorString()); // just do some log

the error message is Image conversion failed. Error::File not found

Any god like developer can help me? I‘m alreay reach the deadline

Axel Spoerl

First of all, please consider upgrading to Qt 6. Qt 5.13 is EOL and out of support. I haven't got a copy of it and my answer is based on Qt 6.

I can just guess what the first problem is, but it looks as if filebyteis emply, or the image reader can't guess the format.
Try debugging the output of QImageReader::supportedFormats(). Check if your image format is still supported. Try setting it explicitly by using e.g. QImage::fromData(filebyte, "image/png").

The image reader attempt wouldn't compile in Qt 6, because the used constructor expects a file name as a QString. There is no (more) constructor of QString taking a byte array, but maybe in 5.13 there was one. I don't know.
In any case, the constructor of the image reader takes a QIODevice *, e.g. a file and a format. In Qt 6, there is no constructor taking a plain byte array with data.

hskoglund

Hi, @Axel-Spoerl : upgrading to Qt6 makes it much more difficult to run the app on Windows 7, so maybe in this case Qt5 is a better choice,
@Neether : Window 7 does not support as many different file formats as Windows 10 and 11 do, try changing from .jpg to .png format.

Christian Ehrlicher

@Neether said in Can not convert A QByteArray to QImage on windows7:

QByteArray filebyte = pReply->readAll();

what is pReply?

Neether

@Christian-Ehrlicher
it's QNetworkReply,I request a image from remote server

Christian Ehrlicher

@Neether And you read it after requestFinished()?
I would save it to a file and try to read it with another image reader. Also make sure the Qt jpeg image plugin is available on your system. (plugins/imageformats folder in your Qt installation).