Generating a random line on a 2d array in python

Question

I've got a 2d array of zeros: 250 by 250. And I want to generate a random straight random line of a specific length (haven't yet decided). Obviously, since it's a line the values that turn from zero to one must be connected in some way, vertically, horizontally, or diagonally; and it also has to be straight. How could I do this? I'm quite stuck with this problem, any help would be appreciated.

So by "line on a 2d array" you mean that the array is like an image of (zero/white) pixels and you want to draw a line by changing pixels (to one/black)? You can only approximate a specific length (and angle), and the way the pixels are adjusted along the angle is also approximate. It won't be too hard to make a function for whatever approximation rules you might come up with, but maybe it'll be simpler to use some existing image editing library. — BatWannaBe
– BatWannaBe, Commented Oct 30, 2021 at 17:54
Do you mean a line of some random length N somewhere in your 2D array, where the line could be at any angle? — ramzeek
– ramzeek, Commented Oct 30, 2021 at 18:05
You could do it with the python library PIL. PIL is a library to manipulate images and also can do simple drawing. You can convert between images and numpy arrays. If you want to do it yourself without a library, it can be very tricky. In that case I suggest to do some reseach, make some attemtps and post the code you have. — nadapez
– nadapez, Commented Oct 31, 2021 at 3:31

ansev · Accepted Answer · 2021-10-30 19:22:27Z

2

We can do:

import numpy as np
SIZE = 250
arr = np.zeros((SIZE, SIZE))
M_POS = np.arange(-SIZE, SIZE)
M_POS = np.r_[M_POS,  1 / M_POS[M_POS!=0]]
M = np.random.choice(M_POS, 1)[0]
N = np.random.choice(np.arange(-SIZE, SIZE), 1)[0]
L = 50
P0 = np.array([0, N])
X_Y  = np.array([1, 1 / M]) if abs(M) < 1 else np.array([1, M])
draw_in = np.add(np.repeat([P0], L, axis=0), 
                 np.repeat([X_Y], L, axis=0) * np.arange(L)[:, np.newaxis]).astype(int)
draw_in = draw_in[((draw_in < SIZE) & (draw_in>0)).all(axis=1)]
arr[draw_in[:, 0], draw_in[:, 1]] = 1

answered Oct 30, 2021 at 19:22

ansev

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ansev Over a year ago

You are wlecome:) I am glad to help Could you consider Accept the answer? @Koza Kurumlu ?

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