[Image-SIG] PIL and converting an image to and from a string value

[Chris Hare]

Thanks! That did it.

The second part of my function is to drop the image in the StringIO buffer into a Tkinter canvas widget.  

If I do this:

self.imageBuffer.seek(0)
image = Image.open(self.imageBuffer)
self.picture1.create_image(0, 0, image = image )

self.picture1 = Canvas(self.pictureFrame,width=150,height=150)

I get:
Exception in Tkinter callback
Traceback (most recent call last):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1410, in __call__
    return self.func(*args)
  File "z.py", line 802, in changePicture1
    self.picture1.create_image(0, 0, image = image )
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 2198, in create_image
    return self._create('image', args, kw)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 2189, in _create
    *(args + self._options(cnf, kw))))
TclError: image "<PngImagePlugin.PngImageFile image mode=RGB size=150x150 at 0x10F1227A0>" doesn't exist

If I change the code to use the image rest from Image.open above to create a TkImage.PhotoImage, 

                self.imageBuffer.seek(0)
                image = Image.open(self.imageBuffer)
                photo = PhotoImage(image)
                self.picture1.create_image(0, 0, image = photo )

I get yet a different exception:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1410, in __call__
    return self.func(*args)
  File "z.py", line 803, in changePicture1
    self.picture1.create_image(0, 0, image = photo )
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 2198, in create_image
    return self._create('image', args, kw)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 2189, in _create
    *(args + self._options(cnf, kw))))
TypeError: __str__ returned non-string (type instance)

Not sure what I got wrong.  Based on what I think I understand fro the man pages and some net searches, I think either case should be okay.


On Apr 27, 2012, at 9:55 AM, Gareth Rees wrote:

> Chris Hare wrote:
>> okay - I have an error but I don't understand what I got wrong:
>> 
>> self.imageBuffer = StringIO.StringIO()
>> image = Image.open(filename)
>> image = image.resize((150,150),Image.ANTIALIAS)
>> image.save(self.imageBuffer, format= 'PNG')
>> image = Image.open(self.imageBuffer)
>> IOError: cannot identify image file
>> 
>> The error occurs when trying to open the imageBuffer so I can work with the data in the buffer.  What have I missed?
> 
> You need to rewind to the start of the buffer before trying to read from it:
> 
> 	self.imageBuffer.seek(0)
> 
> -- 
> Gareth Rees