Question

I’m currently trying to setup a GUI in Tkinter so that I can show a sequence of images (named file01.jpg, file02.jpg, etc. etc.). Currently I’m doing it by creating a Sequence object to manage the list of images that I care about:

class Sequence:
    def __init__(self,filename,extension):
        self.fileList = []
        #takes the current directory
        listing = os.listdir(os.getcwd())
        #and makes a list of all items in that directory that contains the filename and extension
        for item in listing:
            if filename and extension in item:
                self.fileList.append(item)
        #and then sorts them into order
        self.fileList.sort()
        print self.fileList

    def nextImage(self):
        #returns a string with the name of the next image
        return self.fileList.pop(0)

And then I’m using a rather simple Tkinter script I found online to generate the window and place an image there:

window = Tkinter.Tk()
window.title('Image Analysis!')
sequence = Sequence('test','jpg')

image = Image.open("test01.jpg")
image = image.convert('L')
imPix = image.load()
canvas = Tkinter.Canvas(window, width=image.size[0], height=image.size[1])
canvas.pack()
image_tk = ImageTk.PhotoImage(image)
canvas.create_image(image.size[0]//2, image.size[1]//2, image=image_tk)
window.bind("<space>", lambda e: nextFrame(sequence_object=sequence,event=e))
Tkinter.mainloop()

where nextFrame is defined as:

def nextFrame(sequence_object,event=None):
    nextImage = sequence_object.nextImage()
    print 'Next Image is: ',nextImage
    image = Image.open(nextImage)
    image = image.convert('L')
    imPix = image.load()
    image_tk = ImageTk.PhotoImage(image)
    canvas.create_image(image.size[0]//2, image.size[1]//2, image=image_tk)
    canvas.update()

In my python buffer I see the correct image sequence pop up (‘Next Image is: test02,jpg’, etc.) but the new image never pops up!

Does anyone have any explanation for why the image doesn’t pop up?

Thanks!

nathan lachenmyer

Answer 1

Probably what is happening is that the image is getting destroyed by the garbage collector since the only reference to the image is a local variable.

Try keeping a permanent reference to the image, for example:

...
self.image_tk = ImageTk.PhotoImage(image)
...