HSV to RGB Color Conversion

Question

Is there a way to convert HSV color arguments to RGB type color arguments using pygame modules in python? I tried the following code, but it returns ridiculous values.

Answer 1

The Hue argument should also vary from 0-1.

import colorsys
test_color = colorsys.hsv_to_rgb(359/360.0, 1, 1)

Answer 2

That function expects decimal for s (saturation) and v (value), not percent. Divide by 100.

>>> import colorsys

# Using percent, incorrect
>>> test_color = colorsys.hsv_to_rgb(359,100,100)
>>> test_color
(100, -9900.0, -9900.0)

# Using decimal, correct
>>> test_color = colorsys.hsv_to_rgb(1,1,1)
>>> test_color
(1, 0.0, 0.0)

If you would like the non-normalized RGB tuple, here is a function to wrap the colorsys function.

def hsv2rgb(h,s,v):
    return tuple(round(i * 255) for i in colorsys.hsv_to_rgb(h,s,v))

Example functionality

>>> hsv2rgb(0.5,0.5,0.5)
(64, 128, 128)

Answer 3

If you are working with Numpy arrays then matplotlib.colors.hsv_to_rgb is quite direct:

import numpy as np
from matplotlib.colors import hsv_to_rgb
# This will create a nice image of varying hue and value
hsv = np.zeros((512, 512, 3))
hsv[..., 0] = np.linspace(0, 1, 512)
hsv[..., 1] = 1.
hsv[..., 2] = np.linspace(0, 1, 512)[:, np.newaxis]
rgb = hsv_to_rgb(hsv)

Note that the input and output images have values in the range [0, 1].

Answer 4

In opencv, use any of their color conversions. Note that BGR and RGB are flipped in cv2 land.

def convertColor(hsv, conversion):
    return tuple(int(i) for i in cv2.cvtColor(np.uint8([[hsv]]), conversion).flatten())

Usage:

hsvColor = (0,255,255) #bright red
bgrColor = convertColor(hsvColor, cv2.COLOR_HSV2BGR)

Answer 5

OpenCV also offers this possibility. Note that R and B channels are inverted, i.e. BGR. So uses the function that best fits your needs:

import cv2

rgbimg = cv2.cvtColor(hsvimg, cv2.COLOR_HSV2RGB)
bgrimg = cv2.cvtColor(hsvimg, cv2.COLOR_HSV2BGR)

Answer 6

Since the question is tagged pygame, I want to mention that PyGame allows conversion between color schemes. The pygame.Color object can be used to convert between the RGB and HSL/HSV color schemes.

The hsva property:

Gets or sets the HSVA representation of the Color. The HSVA components are in the ranges H = [0, 360], S = [0, 100], V = [0, 100], A = [0, 100].

hsva = pygame.Color((red, green, blue, alpha)).hsva

color = pygame.Color(0)
color.hsva = (hue, saturation, value, alpha)
rgba = (color.r, color.g, color.b, color.a)

The hsla property:

Gets or sets the HSLA representation of the Color. The HSLA components are in the ranges H = [0, 360], S = [0, 100], V = [0, 100], A = [0, 100].

hsla = pygame.Color((red, green, blue, alpha)).hsla

color = pygame.Color(0)
color.hsla = (hue, saturation, lightness, alpha)
rgba = (color.r, color.g, color.b, color.a)

---

Minimal example:

import pygame

pygame.init()

window = pygame.display.set_mode((450, 300))
clock = pygame.time.Clock()

run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    window.fill((255, 255, 255))
    w, h = window.get_size()
    for i in range(6):
        color = pygame.Color(0)
        color.hsla = (i * 60, 100, 50, 100)
        pygame.draw.circle(window, color, 
            (w//6 + w//3 * (i%3), h//4 + h//2 * (i//3)), 
            round(min(window.get_width() * 0.16, window.get_height() * 0.2)))

    pygame.display.flip()

pygame.quit()
exit()