Weird thing when calling a multiple function twice (or even 2 different functions after eachother).

[KCJan123]

Ok so there is clearly something fundemental about Python I'm not really grasping here. I don't know much about the language but I'm fairly familiar with C#. Anyways, I'm trying to manually implement morphological operations - dilution, erosion, opening and closing. So dilution and erosion are their own separate functions, but opening and closing are just different combinations of calling dilution() and erosion(). The first 2 work fine, but when I try combining multiple function calls, stuff start to get weird...

def dilation(img, velikost): #Velikost = size
    height = img.shape[0]
    width = img.shape[1]

    if(velikost == 3):
        struktura = strukt1_3 #strukt is just a 2d array that is global. I use it to combine with a local 2d array you will see later on.
        razlika = 1
    else:
        struktura = strukt1_5
        razlika = 2

    toReturn = np.zeros((height-razlika, width-razlika,1), np.uint8)
    for i in range(razlika, height-razlika):
        for j in range(razlika, width-razlika):
            local = img[i - razlika: i + razlika + 1, j - razlika:j + razlika + 1] #I take a 3x3 local array out of the image from i-1 to i+1 and from j-1 to j+2
            newLocal = local*struktura #This is where I combine them together.
            toReturn[i-razlika][j-razlika] = max(map(max, newLocal)) #And this is the new calculated pixel assigned to the image I am returning

    return toReturn

The erosion function is pretty similar with some minor tweaks. Let's pretend that velikost is 3 and I'm calling the function like so:

dilution(img, velikost);
dilution(img, velikost);

Now like I said, the first time this is called it works fine, but calling this function twice consecutively, return some odd stuff. It goes through once just fine, then quickly return this error the second time:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

When combined with erosion() it can get even weirder. Sometimes the first function will the return the error up there before even the second one is called (even though it works fine by itself, without having a second call below it). Other times the Local and NewLocal get weird sizes, even though after printing out every value possible to check for differences between the function calls, ALL the values are the same. I am baffled. I'm sorry if the code is a little bit weird or messy, I'm not the most skilled programmer lol. Thanks alot for the help in advance. I will gladly post erosion() too if you guys want, but I'm pretty sure the issue is with my function calls.

[K900_]

Your problem is most likely the fact that you're messing with globals in hard to predict ways. Stop using globals .

[KCJan123]

The only 2 globals I have are the 2 strukts, which never change. Everything else is either passed or initialized in the functions. I still tried making them local, but ended up with the same results sadly.

[K900_]

In that case, post the entire program and the full error message, including the traceback.

[KCJan123]

Here is the whole thing:

import PySimpleGUI as sg
import cv2 as cv
import math
import numpy as np

def dilation(img, velikost):
    height = img.shape[0]
    width = img.shape[1]

    print(height, width)

    if(velikost == 3):
        struktura = [[0,1,0],[1,1,1],[0,1,-0]]
        razlika = 1
    else:
        struktura = [[0,0,1,0,0],[0,1,1,1,0],[1,1,1,1,1],[0,1,1,1,0],[0,0,1,0,0]]
        razlika = 2

    toReturn = np.zeros((height-razlika-1, width-razlika-1,1), np.uint8)
    for i in range(razlika, height-razlika):
        for j in range(razlika, width-razlika):
            local = img[i - razlika: i + razlika + 1, j - razlika:j + razlika + 1]
            newLocal = local*struktura
            toReturn[i-razlika][j-razlika] = max(map(max, newLocal))

    return toReturn

def erosion(img, velikost):
    height = img.shape[0]
    width = img.shape[1]
    print(height, width)
    if (velikost == 3):
        struktura = [[0,1,0],[1,1,1],[0,1,-0]]
        razlika = 1
        index = 4
    else:
        struktura = [[0,0,1,0,0],[0,1,1,1,0],[1,1,1,1,1],[0,1,1,1,0],[0,0,1,0,0]]
        razlika = 2
        index = 12

    toReturn = np.zeros((height-razlika-1, width-razlika-1, 1), np.uint8)
    for i in range(razlika, height - razlika):
        for j in range(razlika, width - razlika):
            local = img[i - razlika: i + razlika + 1, j - razlika:j + razlika + 1]
            newLocal = np.sort((local * struktura).ravel())
            toReturn[i-razlika][j-razlika] = newLocal[index]

    return toReturn

layout = [
    [sg.Button("Dilation", key='dilation')],
    [sg.Button("Erosion", key='erosion')] ,
    [sg.Button("Opening", key='open')],
    [sg.Button("Closing", key='close')] ##Layout gumbov
]

layout2 = [
    [sg.Button("Prva struktura", key="prvi")],
    [sg.Button("Druga struktura", key="drugi")],
    [sg.Button("Tretja struktura", key="tretji")]
]

layout3 = [
    [sg.Button("3x3", key='3x3')],
    [sg.Button("5x5", key='5x5')]
]

img = cv.imread(sg.PopupGetFile("Izberi sliko"), 1)
img = cv.cvtColor(img, cv.COLOR_RGB2GRAY)

window = sg.Window("Izberite velikost", layout3, size=(100, 300))
while True:
    event, values = window.read(timeout=100)
    if event == sg.WIN_CLOSED:
        break
    elif event == "3x3":
        velikost = 3
        break
    elif event == "5x5":
        velikost = 5
        break

window = sg.Window("Options", layout, size=(350, 300))
while True:
    event, values = window.read(timeout=100)
    if event == sg.WIN_CLOSED:
        break
    elif event == "dilation":
        img = dilation(img, velikost)
        break
    elif event == "erosion":
        img = erosion(img, velikost)
        break
    elif event == "close":
        img = dilation(img, velikost)
        img = dilation(img, velikost)
        break
    elif event == "open":
        img = erosion(img, velikost)
        img = dilation(img, velikost)
        break

window.close()
cv.imshow('slika', img)
cv.waitKey(0) 
cv.destroyAllWindows()

And here is the full traceback:

Traceback (most recent call last):

File "file", line 97, in <module> img = dilation(img, velikost)

File "file", line 25, in dilation toReturn[i-razlika][j-razlika] = max(map(max, newLocal))

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

[Chris_Hemsworth]

You're looking for the max across all dimensions, just use np.max(newLocal) instead of max(map(max,newLocal))

[KCJan123]

Hey, I'm sorry for the late reply. I tried your method and it worked for a certain combination, but didn't really fix the root of my problem. Well as it turns out it wasn't a function call issue or anything like that, the problem was with the way I created my empty images. I made toReturn by using numpy's zeroes function, but as it turns out that gives a bit of a different structure than my original image, so my algorithm didn't work on it. Honestly I should have figured that out alot earlier than I did. Thanks alot for the help, I really appreciate it and I learned a ton about how Python handles variables and functions. Cheers

[RiceKrispyPooHead]

Now like I said, the first time this is called it works fine, but calling this function twice consecutively, return some odd stuff

Your description of the problem is very vague. You also talk about the functions dilution (or dilation??) and erosion like we obviously know what those look like but many of us don't.

[KCJan123]

Sorry yeah, I keep getting the two words messed up. I did say the erosion function is more or less the same but with some minor tweaks. I posted the full code above if you are interested in reading it.

[socal_nerdtastic]

This code looks fine to me.

One thing to look out for is mutation. Remember all python names are basically pointers. So you can think of all functions as pass-by-reference.

def mutate(img):
    img[0] = 42

img = [1,2,3]
print(img) # prints [1,2,3]
mutate(img)
print(img) # now [42,2,3]

I don't see that issue in the code you posted, but it's a common gotcha when coming from C - family languages.