[PyQt] QPixmap.loadFromData()

[paolo at paolodestefani.it]

Hello
I'm trying to create a item delegate for a sql table (postgres db) 
where i have a field (type bytea) that should contain a PNG image.
This is the code of the create editor method:

def createEditor(self, parent, option, index):
         dd = DisplayDialog(parent)
         ba = index.model().data(index, Qt.DisplayRole)
         if ba:
             pix=QPixmap()
             print("Load", pix.loadFromData(ba, "PNG"))
             dd.lbimage.setPixmap(pix)
         if dd.exec_() == QDialog.Accepted:
             pix=dd.getImage()
             ba = QByteArray()
             buf = QBuffer(ba)
             buf.open(QIODevice.WriteOnly)
             print("Save", pix.save(buf, "PNG"))
             index.model().setData(index, ba, Qt.EditRole)
             index.model().submit()

I want that when te user click in the cell that will contain the PNG 
image and a dialog popup where a can choose an PNG image file. This 
dialog have a label that i used for displaying the image (dd.lbimage)
But when i test this i see:

Load False
Save True

which means (i guess) tha i can store the image in the db converting it 
from PNG to QByteArray but when i retrieve it a can not convert from 
QByteArray to PNG image.

What's wrong in my code ?