canvas - Tkinter create image function error (pyimage1 does not exist)

Question

I'm a student from the outside world with no previous programming experience. I have been learning Python as an extension of my math class. I have been trying to create a program that generates fractals using Tkinter. The code works well on its own, but the inclusion of a user-input GUI causes it to give an error:

    Exception in Tkinter callback
    Traceback (most recent call last):
      File "C:Python33libkinter\__init__.py", line 1475, in __call__
        return self.func(*args)
      File "C:Python33FractalGUI.py", line 74, in fractals
        canvas.create_image((0, 0), image = img, state = "normal", anchor = tkinter.NW)
      File "C:Python33libkinter\__init__.py", line 2319, in create_image
        return self._create('image', args, kw)
      File "C:Python33libkinter\__init__.py", line 2310, in _create
        *(args + self._options(cnf, kw))))
    _tkinter.TclError: image "pyimage1" doesn't exist

The code itself is below. Please note that the error doesn't appear until the canvas.create_image line is run. If there is any other information that I can provide, please let me know. Thanks! :)

    import tkinter
    from tkinter import *

    #Creates widgets for user input
    class Imagespecs(Frame):

        def __init__(self,master):
            Frame.__init__(self,master)
             self.grid()
             self.y_axis()
             self.x_axis()

    #Y axis input
         def y_axis(self):
            self.instruction = Label(self,text = "How many pixels high do you want the image?")
            self.instruction.grid(row = 8, column = 0, columnspan = 2, sticky = N)

            self.height = Entry(self)
            self.height.grid(row = 10, column = 1, sticky = E)

    #Enters info to run fractal generation
            self.submit_button = Button(self,text = "Submit", command = self.fractals)
            self.submit_button.grid(row = 14, column = 2, sticky = E)

    #X axis input
         def x_axis(self):
             self.instruction2 = Label(self,text = "How many pixels wide do you want the image?")
             self.instruction2.grid(row = 4, column = 0, columnspan = 2, sticky = E)

            self.width = Entry(self)
            self.width.grid(row = 6, column = 1, sticky = E)

      #generates fractal
         def fractals(self):
             #Replace non-input
             content = self.width.get()
             content2 = self.height.get()

             if content == "":
                content = 500

             if content2 == "":
                content2 = 500

            #Create window specs
            WIDTH = int(content2); HEIGHT = int(content)
            xa = -2.0; xb = 1.0
            ya = -1.5; yb = 1.5
            maxIt = 256

             window = Tk()
             canvas = Canvas(window, width = WIDTH, height = HEIGHT, bg = "#000000")
             img = PhotoImage(width = WIDTH, height = HEIGHT)

             #The Newton-Raphson iteration
             h = HEIGHT
            for ky in range(HEIGHT):
                print (h)
                h = h - 1
                for kx in range(WIDTH):
                    c = complex(xa + (xb - xa) * kx / WIDTH, ya + (yb - ya) * ky / HEIGHT)
                    z = complex(0.0, 0.0)
                     for i in range(maxIt):
                        z = z * z + c
                        if abs(z) >= 2.0:
                            break
                     rd = hex(i % 4 * 64)[2:].zfill(2)
                     gr = hex(i % 8 * 32)[2:].zfill(2)
                     bl = hex(i % 16 * 16)[2:].zfill(2)
                     img.put("#" + rd + gr + bl, (kx, ky))

             canvas.create_image((0, 0), image = img, state = "normal", anchor = tkinter.NW)

             #Run GUI
             canvas.pack()
             mainloop()

     root = Tk()
     root.title("Fractal GUI")
     root.geometry("300x200")
     app = Imagespecs(root)

     root.mainloop()

Answer 1

Have a try and define a master:

PhotoImage(master = canvas, width = WIDTH, height = HEIGHT)

If you do not define a master then this image uses the first Tk() which is created and if that Tk is deleted there is no image to display.

Tell me if it works, I am guessing.