Difference between revisions of "Wavelength to RGB in Python"
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The input wavelength range is 380 nm through 750 nm (violet through red). | The input wavelength range is 380 nm through 750 nm (violet through red). | ||
− | For testing see [[ | + | For testing see [[canvas.py]]. |
[[Image:spectrum.png|spectrum -- 380 nm through 750 nm]] | [[Image:spectrum.png|spectrum -- 380 nm through 750 nm]] |
Revision as of 03:31, 18 December 2013
Wavelength to RGB in Python
This class converts a given wavelength in nanometers to a 24-bit R,G,B value. This is obviously a very approximate conversion and will not appear the same on every display device.
The input wavelength range is 380 nm through 750 nm (violet through red).
For testing see canvas.py.
wl_to_rgb.py:
#!/usr/bin/env python # vim:set ft=python fileencoding=utf-8 sr et ts=4 sw=4 : See help 'modeline' ''' == A few notes about color == Color Wavelength(nm) Frequency(THz) Red 620-750 400-484 Orange 590-620 484-508 Yellow 570-590 508-526 Green 495-570 526-606 Blue 450-495 606-668 Violet 380-450 668-789 f is frequency (cycles per second) l (lambda) is wavelength (meters per cycle) e is energy (Joules) h (Plank's constant) = 6.6260695729 x 10^-34 Joule*seconds = 6.6260695729 x 10^-34 m^2*kg/seconds c = 299792458 meters per second f = c/l l = c/f e = h*f e = c*h/l Human eye response: S cone: 437 nm M cone: 533 nm L cone: 564 nm rod: 550 nm daytime, light adapted 498 nm at night ''' import sys import os import traceback import optparse import time import logging def wavelength_to_rgb(wavelength, gamma=0.8): '''This converts a given wavelength into an approximate RGB value. The given wavelength is in nanometers. The range of wavelength is 380 nm through 750 nm. Based on code by Dan Bruton http://www.physics.sfasu.edu/astro/color/spectra.html ''' wavelength = float(wavelength) if wavelength >= 380 and wavelength <= 440: attenuation = 0.3 + 0.7 * (wavelength - 380) / (440 - 380) R = ((-(wavelength - 440) / (440 - 380)) * attenuation) ** gamma G = 0.0 B = (1.0 * attenuation) ** gamma elif wavelength >= 440 and wavelength <= 490: R = 0.0 G = ((wavelength - 440) / (490 - 440)) ** gamma B = 1.0 elif wavelength >= 490 and wavelength <= 510: R = 0.0 G = 1.0 B = (-(wavelength - 510) / (510 - 490)) ** gamma elif wavelength >= 510 and wavelength <= 580: R = ((wavelength - 510) / (580 - 510)) ** gamma G = 1.0 B = 0.0 elif wavelength >= 580 and wavelength <= 645: R = 1.0 G = (-(wavelength - 645) / (645 - 580)) ** gamma B = 0.0 elif wavelength >= 645 and wavelength <= 750: attenuation = 0.3 + 0.7 * (750 - wavelength) / (750 - 645) R = (1.0 * attenuation) ** gamma G = 0.0 B = 0.0 else: R = 0.0 G = 0.0 B = 0.0 R *= 255 G *= 255 B *= 255 return (int(R), int(G), int(B)) def main(options=None, args=None): # import ppm_dump # import png_canvas import canvas if options.ppm: canvas = canvas.ppm_canvas(371, 278) canvas.is_ascii = True else: canvas = canvas.png_canvas(371, 278) for wl in range(380, 751): r, g, b = wavelength_to_rgb(wl) for yy in range(0, 278): canvas.pixel(wl - 380, yy, r, g, b) sys.stdout.write(str(canvas)) if __name__ == '__main__': try: start_time = time.time() parser = optparse.OptionParser( formatter=optparse.TitledHelpFormatter(), usage=globals()['__doc__'], version='1' ) parser.add_option( '-v', '--verbose', action='store_true', default=False, help='verbose output' ) parser.add_option( '--png', action='store_true', default=True, help='Output as PNG.' ) parser.add_option( '--ppm', action='store_true', default=False, help='Output as PPM ASCII (Portable Pixmap).' ) (options, args) = parser.parse_args() #if len(args) < 1: # parser.error ('missing argument') if options.verbose: print(time.asctime()) exit_code = main(options, args) if exit_code is None: exit_code = 0 if options.verbose: print(time.asctime()) print('TOTAL TIME IN MINUTES: %f' % ((time.time() - start_time) / 60.0)) sys.exit(exit_code) except KeyboardInterrupt as e: # The user pressed Ctrl-C. raise e except SystemExit as e: # The script called sys.exit() somewhere. raise e except Exception as e: print('ERROR: Unexpected Exception') print(str(e)) traceback.print_exc() os._exit(2)