PIL to Qimage conversion: QImage constructor does not free memory - python-imaging-library

Question

I am developping a Qt application loading pictures with PIL, modifying colors and alpha channels, then converting them as QImage.
Here is the problematic piece of code: normal repeated usage of the ImageQt function: # memory is filled around 7 mB/s
if name == 'main':
while True:
im = Image.open('einstein.png') #small picture
imQt = QtGui.QImage(ImageQt.ImageQt(im)) # convert to PySide.QtGui.QImage
imQt.save('outtest.png')# -> rendered picture is correct
#del(imQt) and del(im) does not change anything
time.sleep(0.02)
The problem here is the crazy memory filling, when the picture is supposed to be erased by the garbage collector. I checked with gc.collect(), but it did not change anything.
This example shows what happends with the imageQt function, but in fact, I noticed this is a problem caused by QImage: if you repeatedly use the QImage constructor with data, the memory used by python process increases: im= Image.load('mypic.png').convert('RGBA')
data = im.toString('raw','RGBA')
qIm = QtGui.QImage(data,im.size[0],im.size[1],QtGui.QImage.Format_ARGB32)
qIm.save('myConvertedPic.png')# -> picture is perfect
If you put this code in a loop, memory will increase, as 1st example. From there i am a bit lost because this is a PySide problem...
I tried to use a workaround, but it does not work either:
#Workaround, but not working ....
if name == 'main':
while True:
im = Image.open('einstein.png') #small picture
imRGBA = im.convert('RGBA') # convert to RGBA
imRGBA.save('convtest.png') # ->picture is looks perfect
imBytes = imRGBA.tostring('raw','RGBA')
#print("size %d %d" % (imRGBA.size[0],imRGBA.size[1]))
qImage = QtGui.QImage(imRGBA.size[0],imRGBA.size[1],QtGui.QImage.Format_ARGB32) # create new empty picture
qImage.fill(QtCore.Qt.blue) # fill with blue, otherwise it catches pieces of the picture still in memory
loaded = qImage.loadFromData(imBytes,'RGBA') # load from raw data
print("success %d" % loaded)# -> returns 0
qImage.save('outtest.png')# -> rendered picture is blue
time.sleep(0.02)
I am really stuck here, if you could help find a solution with this workaround ? Because I'm really stuck here!
Also I would like to discuss the QImage problem. Is there any reliable way to free this memory ? Could the fact I am using python3.2(32bits) be a problem in this case ? Am I the only one in this case ?
The imports I am using in case of:
import time
import sys
import PySide
sys.modules['PyQt4'] = PySide # this little hack allows to solve naming problem when using PIL with Pyside (instead of PyQt4)
from PIL import Image, ImageQt
from PySide import QtCore,QtGui

Answer 1

After further unsuccessful searching, I noticed, that the PIL function image.tostring() associated with a QImage constructor caused this problem
im = Image.open('einstein.png').convert('RGBA')
data = im.tostring('raw','RGBA') # the tostring() function is out of the loop
while True:
imQt = QtGui.QImage(data,im.size[0],im.size[1],QtGui.QImage.Format_ARGB32)
#imQt.save("testpic.png") #image is valid
time.sleep(0.01)
#no memory problem !I think I am really close to find what is wrong, but I cannot point it out.
It definitely has something to do with the data variable being held in memory.