Weird, weird, QT jpeg can't work on my friend's PC
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I am finishing a QT app, but I encounted a problem. Here is it:

I use this code to load image into a QGraphicsScene:

    QFile file(fileName);
            if(file.open(QFile::ReadOnly)){
                QByteArray data=file.readAll ();
                pixmapItem.loadFromData (data,"jpeg");
            }

It WORKS on my computer, but when I give this app to my friend, he just can't show this image.I googled and stackovered about this issue which sounds like I need jpeg plugins. 

So, I do this:

1. I copy qjpeg4.dll from C:\QtSDK\QtCreator\bin\imageformats into my app root dir.---->failed.
2. I copy entire imageformats directory as a subdirectory of my app toor dir. ---->also failed.

So, how can I distribute my app to my friends? It works in my computer, so, it can do work on others', can't it?