[Solved]QImage fail to read jpeg--dll deploy problem

ChrisW67

No, it does not need a special library. Assuming that get_image_name(image_url) produces a valid file name (without path) for the host system the file will be written into the current working directory of the process. On Windows 7 attempts to write to protected locations will either fail (manifest in program) or be redirected (no manifest). Either way the file will not be where you expect it. Check this first.

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Thanks for your reply, but the problem is not because it can't save the image but the
QImage failed to recognize "it is a jpg"

@
//the QImage is "null " even the size of the QByteArray are the same, on my
//PC, virtual box, and the other's PC
image.loadFromData(reply->readAll() );
@

@
image.loadFromData(reply->readAll(), "jpg"); //still fail
@

Whatever, the size of the QImage is always (0, 0) on other pc
but my pc work perfectly good, don't know what is happening

JKSH

Let's debug, step-by-step.

First, pass the result of QNetworkReply->readAll() to QFile::write(). Has the image downloaded correctly? Can you open the image in your computer?

If it doesn't work, then something's wrong with the download.
If it does works, then the problem is not in QNetworkAccessManager (so you should change your title).

Also, please provide details on how you "release the binary to other computer"?

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Thanks for your advices, I change the codes to

@
QImage image;
QString const image_url = reply->url().toString();
QByteArray image_array = reply->readAll();
image.loadFromData(image_array); //fail to load the image_array

QFile file&#40;"temp"&#41;;

if ( !file.exists()) qDebug() << "can't find";

if(!file.open(QIODevice::WriteOnly) ) qDebug() << "can't open";

file.write(image_array); //but the data could be save and display by other software

@

Maybe I should change the title to "QImage fail to read jpeg"

ChrisW67

Chances are you have not deployed the image format plugins (not that you really need them to save the downloaded image as JKSH points out).

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I release my program with the items as follow

1 : release with the exe compile by mingw4.6.2
2 : put other's dll in the same folder
libgcc_s_dw2-1.dll, libstdc++-6.dll, mingwm10.dll, QtCore4.dll, QtGui4.dll, QtNetwork4.dll

Test it on Virtual box and other pc, make sure it has the same behaviour on my pc

JKSH

Yup, that's a better title :) whi

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I make the codes become easier to read
@
int main(int argc, char *argv[])
{
QApplication a(argc, argv);

QImage image("temp.jpg");
qDebug() << image.size(); //the size is (0, 0) even the jpg can be read by other software
image.save("haha");

return a.exec(&#41;;

}
@

on my pc, it works prefectly, but other pc just don't work

JKSH

Interesting...

Try this and see if you can get any useful info:
@
qDebug() << "Supported formats:" << QImageReader::supportedImageFormats();

QImageReader reader("temp.jpg");
qDebug() << "Can read file?:" << reader.canRead();

QImage image = reader.read();
qDebug() << reader.errorString();
@

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Weird, extremely weird，same dll, same exe, same os

on my pc, the answer are

bq. Supported formats: ("bmp", "gif", "ico", "jpeg", "jpg", "mng", "pbm", "pgm", "pn
g", "ppm", "svg", "svgz", "tga", "tif", "tiff", "xbm", "xpm")
Can read file?: true
"Unknown error"

on other pc, the answer are

Supported formats: ("bmp", "pbm", "pgm", "png", "ppm", "xbm", "xpm")
Can read file?: false
"Unsupported image format"

JKSH

Try copying C:[Qt-installation]\4.8.2\plugins\qjpeg4.dll

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I copy the dll of plugins into the folder, but the QImage still don't support jpg

JKSH

http://www.qtcentre.org/threads/32614-DLL-Deploying-problems

Sounds like they succeeded when they put qjpeg4.dll inside a subdirectory called "imageformats"

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Thanks a lot, the problem solved.