[python] Generate random colors (RGB)

I just picked up image processing in python this past week at the suggestion of a friend to generate patterns of random colors. I found this piece of script online that generates a wide array of different colors across the RGB spectrum.

def random_color():
    levels = range(32,256,32)
    return tuple(random.choice(levels) for _ in range(3))

I am simply interesting in appending this script to only generate one of three random colors. Preferably red, green, and blue.

Output in the form of (r,b,g) its look like (255,155,100)

from numpy import random
color = (random.randint(0, 255), random.randint(0, 255), random.randint(0, 255))

Inspired by other answers this is more correct code that produces integer 0-255 values and appends alpha=255 if you need RGBA:

tuple(np.random.randint(256, size=3)) + (255,)

If you just need RGB:

tuple(np.random.randint(256, size=3))

Taking a uniform random variable as the value of RGB may generate a large amount of gray, white, and black, which are often not the colors we want.

The cv::applyColorMap can easily generate a random RGB palette, and you can choose a favorite color map from the list here

Example for C++11:

#include <algorithm>
#include <numeric>
#include <random>
#include <opencv2/opencv.hpp>

std::random_device rd;
std::default_random_engine re(rd());

// Generating randomized palette
cv::Mat palette(1, 255, CV_8U);
std::iota(palette.data, palette.data + 255, 0);
std::shuffle(palette.data, palette.data + 255, re);
cv::applyColorMap(palette, palette, cv::COLORMAP_JET);

// ...

// Picking random color from palette and drawing
auto randColor = palette.at<cv::Vec3b>(i % palette.cols);
cv::rectangle(img, cv::Rect(0, 0, 100, 100), randColor, -1);

Example for Python3:

import numpy as np, cv2

palette = np.arange(0, 255, dtype=np.uint8).reshape(1, 255, 1)
palette = cv2.applyColorMap(palette, cv2.COLORMAP_JET).squeeze(0)
np.random.shuffle(palette)
# ...

rand_color = tuple(palette[i % palette.shape[0]].tolist())
cv2.rectangle(img, (0, 0), (100, 100), rand_color, -1)

If you don't need so many colors, you can just cut the palette to the desired length.

With custom colours (for example, dark red, dark green and dark blue):

import random

COLORS = [(139, 0, 0), 
          (0, 100, 0),
          (0, 0, 139)]

def random_color():
    return random.choice(COLORS)

color = lambda : [random.randint(0, 255), random.randint(0, 255), random.randint(0, 255)]

import random
rgb_full="(" + str(random.randint(1,256))  + "," + str(random.randint(1,256))  + "," + str(random.randint(1,256))  + ")"

A neat way to generate RGB triplets within the 256 (aka 8-byte) range is

color = list(np.random.choice(range(256), size=3))

color is now a list of size 3 with values in the range 0-255. You can save it in a list to record if the color has been generated before or no.

You could also use Hex Color Code,

Name    Hex Color Code  RGB Color Code
Red     #FF0000         rgb(255, 0, 0)
Maroon  #800000         rgb(128, 0, 0)
Yellow  #FFFF00         rgb(255, 255, 0)
Olive   #808000         rgb(128, 128, 0)

For example

import matplotlib.pyplot as plt
import random

number_of_colors = 8

color = ["#"+''.join([random.choice('0123456789ABCDEF') for j in range(6)])
             for i in range(number_of_colors)]
print(color)

['#C7980A', '#F4651F', '#82D8A7', '#CC3A05', '#575E76', '#156943', '#0BD055', '#ACD338']

Lets try plotting them in a scatter plot

for i in range(number_of_colors):
    plt.scatter(random.randint(0, 10), random.randint(0,10), c=color[i], s=200)

plt.show()