[PYTHON] Color code list

Color code list

Since I studied about colors, I made a list of color codes.

--Note) The following is a list of color codes for Web Safe Colors (explained below). --Note) The range of possible values for HSV is $ 0 \ le H \ le 360, ~~ 0 \ le S, V \ le 255 $.

Python code

The above list is a copy and paste of the output result of the following Python code. The environment used was Google Colaboratory.

print('|Color code| $(R, G, B)$ | $(H, S, V)$ |Complementary colors|Opposite color|')
print('| :---: | :--- | :--- | :---: | :---: |')
for r in range(0, 256, 51):
  for g in range(0, 256, 51):
    for b in range(0, 256, 51):
      r_c, g_c, b_c = get_complementary_colors(r, g, b)
      r_o, g_o, b_o = get_opposite_colors(r, g, b)
      h, s, v = get_hsv_colors(r, g, b)
      color_code = '`#' + format(r, '02x') + format(g, '02x') + format(b, '02x') + '`' #Convert to hexadecimal
      rgb = '$({}, {}, {})$'.format(r, g, b)
      hsv = '$({}, {}, {})$'.format(h, s, v)
      color_code_comp = '`#' + format(r_c, '02x') + format(g_c, '02x') + format(b_c, '02x') + '`'
      color_code_opposit = '`#' + format(r_o, '02x') + format(g_o, '02x') + format(b_o, '02x') + '`'
      print('| {} | {} | {} | {} | {} |'.format(color_code, rgb, hsv, color_code_comp, color_code_opposit))

The function is:

def get_complementary_colors(r, g, b):
  """Function to calculate complementary colors"""
  tmp = max(r, g, b) + min(r, g, b)
  return tmp - r, tmp - g, tmp - b

def get_opposite_colors(r, g, b):
  """Function to calculate the opposite color"""
  return 255 - r, 255 - g, 255 - b

def get_hsv_colors(r, g, b):
  """
Function to calculate HSV
Use a cylinder model
  h, s,The range of possible values for v is
  h : 0 - 360
  s : 0 - 255
  v : 0 - 255
And
  """
  r /= 255
  g /= 255
  b /= 255
  max_rgb = max(r, g, b)
  min_rgb = min(r, g, b)
  v = max_rgb
  if v == 0 or v == min_rgb:
    h = 0
    s = 0
  else:
    s = (max_rgb - min_rgb) / max_rgb
    if min_rgb == b:
      h = 60 * (g - r)/(max_rgb - min_rgb) + 60
    elif min_rgb == r:
      h = 60 * (b - g)/(max_rgb - min_rgb) + 180
    elif min_rgb == g:
      h = 60 * (r - b)/(max_rgb - min_rgb) + 300
  h %= 360
  s *= 255
  v *= 255
  return int(h), int(s), int(v)

For HSV, the same result can be obtained by the following calculation using OpenCV.

import cv2
import numpy as np

def get_hsv_colors_cv2(r, g, b):
  """Function to calculate HSV (using OpenCV)"""
  bgr = np.uint8([[[b, g, r ]]])
  hsv = cv2.cvtColor(bgr, cv2.COLOR_BGR2HSV)
  h = hsv[0][0][0]
  s = hsv[0][0][1]
  v = hsv[0][0][2]
  h *= 2 #0 in openCV-For 180
  return h, s, v

Web safe color

Web-safe colors are colors that are displayed in the same way even in different environments such as browsers and operating systems. RGB is divided into 6 levels (00, 33, 66, 99, CC, FF in hexadecimal notation), and the colors can be combined. There are 216 colors in all.

RGB RGB is a method of expressing colors by combining the three colors of red (** R ** ed), green (** G ** reen), and blue (** B ** lue). It is a general color expression method.

HSV HSV is a method of expressing color by combining three of hue (** H ** ue), saturation (** S ** saturation), and lightness (** V ** alue).

RGB to HSV conversion

Source: HSV color model

The conversion formula from RGB space to HSV space is as follows. MAX and MIN are the maximum and minimum values of RGB, respectively.

\begin{eqnarray}
H &=&
\begin{cases}
{\rm undefined},       &({\rm when ~~~} {\rm MIN} = {\rm MAX})\\
60 \times \displaystyle\frac{G - R}{{\rm MAX}-{\rm MIN}}+60, &({\rm when ~~~}{\rm MIN} = B)\\
60 \times \displaystyle\frac{B - G}{{\rm MAX}-{\rm MIN}}+180, &({\rm when ~~~}{\rm MIN} = R)\\
60 \times \displaystyle\frac{R - B}{{\rm MAX}-{\rm MIN}}+300, &({\rm when ~~~}{\rm MIN} = G)
\end{cases}\\
\\
S &=& \frac{{\rm MAX}-{\rm MIN}}{{\rm MAX}}\\
\\
V &=& {\rm MAX}
\end{eqnarray}

However, since $ 0 \ le R, G, B \ le 1 $ is required, $ R, G, B $ are divided by $ 255 $ in advance.

Also, since it is $ 0 \ le H \ le 360 $, we need to finally allocate the remainder divided by $ 360 $ to $ H $.

#Example
H = 400 # > 360
print(H % 360)
#40
H = -30 # < 0
print(H % 360)
#330

Complementary colors

Complementary colors are the sum of the maximum and minimum RGB values minus the respective RGB values.

Example) RGB = (100, 255, 50) in the case of, The value is subtracted from the value 305, which is the sum of the maximum value 255 and the minimum value 50. 305 - 100 = 205 305 - 255 = 50 305 - 50 = 255 Is a complementary color RGB = (205, 50, 255) Will be.

Opposite color

The opposite color is 255 minus the RGB values.

Example) RGB = (100, 255, 50) in the case of, Each value was subtracted from 255 255 - 100 = 155 255 - 255 = 0 255 - 50 = 205 Is the opposite color RGB = (155, 0, 205) Will be.

reference

-HSV Color Space -Color wheel and 12 color wheel [Creation and calculation formula]