[Solved] QImage.save() generates strange image files

[Edgard]

I'm trying to make a very simple image creator, using PySide.
For now, my app can draw things. But it fails to save a image file.
According to the PySide documentation, using QImage.save() would result in the desired result. So, I wrote this script. It generates a 100x100 image with red background:

@
#!/usr/bin/python

-- coding: utf-8 --

import sys
from PySide.QtCore import *
from PySide.QtGui import *

app = QApplication(sys.argv)

size = QSize(100,100)
picture = QImage(size, QImage.Format_RGB32)
painter = QPainter()
painter.begin(picture)
brush = QBrush()
color = QColor(255,0,0)
brush.setColor(color)
painter.setBackground(brush)
painter.end()
picture.save("image.png")

exit()

app.exec_()
sys.exit()
@

However, it fails to create the image.
Actually, it generates a image file. But the image file is not the one expected; it generates a black background, and some "blue lines" on the top of the image, instead.
Does someone know what could be causing this?

[Edgard]

Found the solution!
The script isn't generating a image file properly because It doesn't has a QImage.fill(). Upon declaring one, the script generates the image correctly.
The following script (a modified version of the first script I posted) does what I needed:

@
#!/usr/bin/python

-- coding: utf-8 --

import sys
from PySide.QtCore import *
from PySide.QtGui import *

app = QApplication(sys.argv)

size = QSize(100,100)
picture = QImage(size, QImage.Format_RGB32)
picture.fill(32)
picture.setAlphaChannel(picture)

painter = QPainter()
painter.begin(picture)
painter.setRenderHint(QPainter.Antialiasing)
painter.setBackgroundMode(Qt.TransparentMode)
pen = QPen()
color = QColor(255,0,0)
pen.setColor(color)
pen.setWidth(5)
pen.setCapStyle(Qt.RoundCap)
painter.setPen(pen)
painter.drawEllipse(10,10, 80,80)
painter.end()

imagefile = QImageWriter()
imagefile.setFileName("circle")
imagefile.setFormat("png")
imagefile.setQuality(100)
imagefile.write(picture)

exit()

app.exec_()
sys.exit()
@