1  # SPDX-FileCopyrightText: Copyright (c) 2022 JG for Cedar Grove Maker Studios
 2  #
 3  # SPDX-License-Identifier: MIT
 4  """
 5  `cedargrove_rgb_spectrumtools.grayscale`
 6  ================================================================================
 7  
 8  Spectral Index to Grayscale RGB Converter Helper
 9  
10  * Author(s): JG
11  
12  Implementation Notes
13  --------------------
14  
15  **Hardware:**
16  
17  **Software and Dependencies:**
18  
19  * Adafruit CircuitPython firmware for the supported boards:
20    https://circuitpython.org/downloads
21  
22  """
23  
24  __version__ = "0.0.0+auto.0"
25  __repo__ = "https://github.com/CedarGroveStudios/CircuitPython_RGB_SpectrumTools.git"
26  
27  
28  def map_range(x, in_min, in_max, out_min, out_max):
29      """
30      Maps and constrains an input value from one range of values to another.
31      (from adafruit_simpleio)
32  
33      :param float x: The value to be mapped. No default.
34      :param float in_min: The beginning of the input range. No default.
35      :param float in_max: The end of the input range. No default.
36      :param float out_min: The beginning of the output range. No default.
37      :param float out_max: The end of the output range. No default.
38  
39      :return: Returns value mapped to new range
40      :rtype: float
41      """
42      in_range = in_max - in_min
43      in_delta = x - in_min
44      if in_range != 0:
45          mapped = in_delta / in_range
46      elif in_delta != 0:
47          mapped = in_delta
48      else:
49          mapped = 0.5
50      mapped *= out_max - out_min
51      mapped += out_min
52      if out_min <= out_max:
53          return max(min(mapped, out_max), out_min)
54      return min(max(mapped, out_max), out_min)
55  
56  
57  def index_to_rgb(index=0, gamma=0.8):
58      """
59      Converts a spectral index to a grayscale RGB value. Spectral index in
60      range of 0.0 to 1.0. Gamma in range of 0.0 to 1.0 (1.0=linear),
61      default 0.8 for color TFT displays.
62  
63      :param float index: The normalized index value, range 0 to 1.0. Defaults to 0.
64      :param float gamma: The gamma color perception value. Defaults to 0.8.
65  
66      :return: Returns a 24-bit RGB value
67      :rtype: integer
68      """
69  
70      red = grn = blu = map_range(index, 0, 1.0, 0.1, 1.0) ** gamma
71  
72      return (int(red * 255) << 16) + (int(grn * 255) << 8) + int(blu * 255)