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Load blob image data into QPixmap

I am writing a program using PyQt4 for front-end GUI and this program accesses a back-end database (which can be either MySQL or SQLite). I need to store some image data in the database and below is the Python code I use to import image files (in JPEG format) to a blob data field in the database:

def dump_image(imgfile):
    i = open(imgfile, 'rb')
    i.seek(0)
    w = i.read()
    i.close()
    return cPickle.dumps(w,1)

blob = dump_image(imgfile)
hex_str = blob.encode('hex') 
# x"%s"%hex_str will be the string inserted into the SQL command

This part works fine. My question is about how to create a QPixmap object from the image data stored in the database in PyQt4. My current approach involves the following steps:

(1) Hex str in database -- cPickle&StringIO --> PIL Image Object

def load_image(s):
    o = cPickle.loads(s)
    c = StringIO.StringIO()
    c.write(o)
    c.seek(0)
    im = Image.open(c)
    return im

(2) PIL Image Object -->Temporary image file

(3) Temporary image file --> QPixmap

This approach also works fine. But it would be better if I don't have to write/read temporary image files which may slow down the program response to user interactions. I guess I could use QPixmap::loadFromData() to directly load from the blob data stored in the database and hope someone here could show me an example on how to use this function.

TIA,

Bing

like image 453
Bing Jian Avatar asked Aug 19 '09 15:08

Bing Jian


1 Answers

You can use the QImage.fromData static method to load an image from a string and then convert it to a pixmap:

 image_data = get_image_data_from_blob()
 qimg = QtGui.QImage.fromData(image_data)
 pixmap = QtGui.QPixmap.fromImage(qimg)
like image 100
Ants Aasma Avatar answered Sep 30 '22 12:09

Ants Aasma