How to draw a circle on image using numpy only, without using anyother library.

Question

0.00/5 (No votes)

See more:

how to draw a circle on image using numpy only, without using anyother library.

What I have tried:

from PIL import Image image=Image.open("rgb.png") arr=np.array(image) arr[50,50]=[255] arr[50,30]=[255] '''for i in range(50): arr[i,50-i-1]=[255]''' arr[30,50]=[255] arr[50,70]=[255] arr[70,50]=[255] img=Image.fromarray(arr,"RGB") img.save('arr.png') img.show()

Posted 25-Aug-22 18:28pm

Member 15667238

Updated 25-Aug-22 21:28pm

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Answer 1 · 2022-08-25T19:08:00

Drawing a circle is easy: all you need is a loop and the right equations:

px = cx + r * cos(a)
py = cy + r * sin(a)

Where the center of the circle with radius r is (cx, cy), and a is the angle which changes as you go round the circle drawing the points / lines (px, py).
The smaller the change in angle each time round your loop, the better the resolution of the circle.
So if you want a circle that is actually square, the angle has five values: 0^o, 90^o, 180^o, 270^o, and 360^o (or their equivalent in radians) though the first and last will generate the same point. More pints, better looking circle - as the number of points you need obviously increases as the radius of the circle does because the length of its circumference is proportional to that radius.

CPallini · Answer 2 · 2022-08-25T21:28:00

Quote:
okay, but how to draw the circle in numpy array.

Try

Python

from PIL import Image
import numpy as np
image=Image.open("rgb.png")
arr=np.array(image)

r = image.width/2 # the radius of the circle (assuming a square image)

for angle in np.arange(0, 2 * np.pi, 1/2/r):
  x = int(r-1 + r * np.cos(angle))
  y = int(r-1 + r * np.sin(angle))
  arr[x,y] = [255]

img=Image.fromarray(arr,'RGB')
img.save('arr.png')
img.show()

How to draw a circle on image using numpy only, without using anyother library.

2 solutions

Solution 1

Solution 2

Add your solution here

Preview 0