Cannot construct tkinter.PhotoImage from PIL Image

Question

I try to show a image in a label when I push a button, but the image are too large and I have tried to resize the image. I have created this function:

def image_resize(imageFile):
    width = 500
    height = 300
    image = Image.open(imageFile)
    im2 = image.resize((width, height), Image.ANTIALIAS)
    return im2

To show the image I have created this function:

def show_image():
    label_originalimage ['image'] = image_tk

And the button with the command=show_image:

filename = 'bild_1.jpg'
image_resize = image_resize(filename)
image_tk = PhotoImage(image_resize)
button_open = Button(frame_open, text='Open Image', command=show_image)

I get only this:

TypeError : __str__ returned non-string (type instance)

Answer 1

The PhotoImage class from tkinter takes a filename as an argument, and as it cannot convert the image into a string, it complains. Instead, use the PhotoImage class from the PIL.ImageTk module. This works for me:

from tkinter import *
from PIL import ImageTk, Image

def image_resize(imageFile):
    width = 500
    height = 300
    image = Image.open(imageFile)
    im2 = image.resize((width,height), Image.ANTIALIAS)
    return im2

def show_image():
    label_originalimage ['image'] = image_tk

root = Tk()
filename = './Pictures/Space/AP923487321702.jpg'
image_resize = image_resize(filename)
image_tk = ImageTk.PhotoImage(image_resize)

label_originalimage = Label(root)
label_originalimage.pack()

button_open = Button(root, text='Open Image', command=show_image)
button_open.pack()

root.mainloop()

Notice the change from image_tk = PhotoImage(image_resize) to image_tk = ImageTk.PhotoImage(image_resize).

Answer 2

I had the same problem when I try to construct a canvas image item for tkinter from a tkinter PhotoImage. The latter was constructed from some image data in memory (in my case an opencv image). The same exception occurs if I simply try to convert the PhotoImage to a string.

I guess there is a bug in the conversion method __str__ of the PhotoImage, making it simply returns the image source. If constructed from a file name (see below) this works fine. If constructed from some image data, this is not of type string and yields an exception.

Unfortunately, using the compatible PhotoImage from PIL's ImageTk module like matsjoyce suggested didn't help me either because I experienced an even worse problem, probably a platform or library version dependent bug (I used OS X 10.11.6, python 3.5, tkinter 8.6, PIL 1.1.7): Now the python script crashed at the construction of the canvas image item with a "Bus Error".

The only workaround I am aware of was to store the image data into a temporary file and use a tkinter PhotoImage constructed from that file name. (Trying the same with the PIL PhotoImage still crashes.)

#!/usr/bin/env python3

import tkinter
import tempfile
import cv2

def opencv2photoimg(opencv_img):
    """Convert OpenCV (numpy) image to tkinter photo image."""
    # ugly workaround: store as file & load file, because direct
    # construction leads to a crash on my platform 
    tmpfile = tempfile.NamedTemporaryFile(suffix='.png', delete=True)
    # ^^^ I am using PNGs only, you might want to use another suffix
    cv2.imwrite(tmpfile.name, opencv_img)
    return tkinter.PhotoImage(file=tmpfile.name)

# load image
img = cv2.imread('test.png')
# do something w/ the image ...

# setup tk window w/ canvas containing an image
root = tkinter.Tk()
canvas = tkinter.Canvas(root, width=img.shape[1], height=img.shape[0])
canvas.pack()
# keep reference to PhotoImage to avoid it being garbage collected
# (well known tkinter bug for canvas image items)
photo_img = opencv2photoimg(img)
# create a canvas item 
img_item = canvas.create_image(0, 0, anchor=tkinter.NW, image=photo_img)

# display the window
tkinter.mainloop()

I do not think it's elegant, but it works.

Answer 3

Yes it works, but yeeeucchh - what I way to have to do it.

Surely there is a better way.

Here is my test code I got to starting from here....

import tkinter
from PIL import Image
import numpy
import time
import io
#python2 version (original) -> 120fps
#full physical file io and new image each cycle -> 130fps
#reuse PIL Image instead of create new each time -> 160fps

class mainWindow():
    times=1
    timestart=time.clock()
    data=numpy.array(numpy.random.random((400,500))*100,dtype=int)
    theimage = Image.frombytes('L', (data.shape[1],data.shape[0]),data.astype('b').tostring())



 def __init__(self):
        self.root = tkinter.Tk()
        self.frame = tkinter.Frame(self.root, width=500, height=400)
        self.frame.pack()
        self.canvas = tkinter.Canvas(self.frame, width=500,height=400)
        self.canvas.place(x=-2,y=-2)
        self.root.after(0,self.start) # INCREASE THE 0 TO SLOW IT DOWN
        self.root.mainloop()

    def start(self):
        global data
        global theimage
        self.theimage.frombytes(self.data.astype('b').tobytes())
        self.theimage.save('work.pgm')
        self.photo = tkinter.PhotoImage(file='work.pgm')
        self.canvas.create_image(0,0,image=self.photo,anchor=tkinter.NW)
        self.root.update()
        self.times+=1
        if self.times%33==0:
            print("%.02f FPS"%(self.times/(time.clock()-self.timestart)))
        self.root.after(10,self.start)
        self.data=numpy.roll(self.data,-1,1)

if __name__ == '__main__':
    x=mainWindow()

Answer 4

Here it is: I found that the input data to photoimage can be a byte array that looks like a ppm file, although it only appears to work on a subset of legal ppm (e.g. 16 bit values don't work)

So for future reference.......

import tkinter
import numpy
import time
#python2 version (original) -> 120fps
#full physical file io and new image each cycle -> 130fps
#reuse PIL Image instead of create new each time -> 160fps
#and... direct image into tkinter using ppm byte array -> 240 fps

class mainWindow():
    times=1
    timestart=time.clock()
    data=numpy.array(numpy.random.random((400,500))*900,dtype=numpy.uint16)

    def __init__(self):
        self.root = tkinter.Tk()
        self.frame = tkinter.Frame(self.root, width=500, height=400)
        self.frame.pack()
        self.canvas = tkinter.Canvas(self.frame, width=500,height=400)
        self.canvas.place(x=-2,y=-2)
        xdata = b'P5 500 400 255 ' + self.data.tobytes()
        self.photo = tkinter.PhotoImage(width=500, height=400, data=xdata, format='PPM')
        self.imid = self.canvas.create_image(0,0,image=self.photo,anchor=tkinter.NW)
        self.root.after(1,self.start) # INCREASE THE 0 TO SLOW IT DOWN
        self.root.mainloop()

    def start(self):
        global data
        xdata = b'P5 500 400 255 ' + numpy.clip(self.data,0,255).tobytes()
        self.photo = tkinter.PhotoImage(width=500, height=400, data=xdata, format='PPM')
        if True:
            self.canvas.itemconfig(self.imid, image = self.photo)
        else:
            self.canvas.delete(self.imid)
            self.imid = self.canvas.create_image(0,0,image=self.photo,anchor=tkinter.NW)
        self.times+=1
        if self.times%33==0:
            print("%.02f FPS"%(self.times/(time.clock()-self.timestart)))
        self.root.update()
        self.root.after(0,self.start)
        self.data=numpy.roll(self.data,-1,1)

if __name__ == '__main__':
    x=mainWindow()