rainbow_vtrgb.py

#! /usr/bin/python3
"""
 rainbow_vtrgb
 animates vt colors like a rainbow
 only useful with something else that updates the whole screen
 (wondering if fbconsole has an ioctl or something like that to force the whole bitmap to update)
"""

import subprocess as sp
import time
import copy

MUL_SAT = 0.5
MUL_VAL = 1.0
MIN_SAT = 1.0
MIN_VAL = 0.2
ANGLE_STEP = 2.0
DELAY=1.0/30.0
DBG=False
VGA_VALS = [
    [0,170,0,170,0,170,0,170,85,255,85,255,85,255,85,255], #R
    [0,0,170,85,0,0,170,170,85,85,255,255,85,85,255,255 ], #G
    [0,0,0,0,170,170,170,170,85,85,85,85,255,255,255,255], #B
]
TRIPLES = list(zip(*VGA_VALS))


def hsv_to_rgb(h, s, v):
    # stolen from https://stackoverflow.com/questions/24852345/hsv-to-rgb-color-conversion
    if s == 0.0: return (v, v, v)
    i = int(h*6.) # XXX assume int() truncates!
    f = (h*6.)-i; p,q,t = v*(1.-s), v*(1.-s*f), v*(1.-s*(1.-f)); i%=6
    if i == 0: return (v, t, p)
    if i == 1: return (q, v, p)
    if i == 2: return (p, v, t)
    if i == 3: return (p, q, v)
    if i == 4: return (t, p, v)
    if i == 5: return (v, p, q)
    
    
def main():
    angle = 0.0

    while (True):
        final_colors = []
        for triple in TRIPLES:
            mulval = hsv_to_rgb(angle/360.0, MUL_SAT, MUL_VAL)
            minval = [x*255 for x in hsv_to_rgb(angle/360.0, MIN_SAT, MIN_VAL)]
            if DBG: print(triple, mulval, minval)
            color = [triple[0] * mulval[0], triple[1]*mulval[1], triple[2]*mulval[2],]
            color = [max(color[0], minval[0]), max(color[1], minval[1]), max(color[2], minval[2]),]
            color = [int(x) for x in color]
            final_colors.append(color)
        final_split = zip(*final_colors)
        if DBG: print(f"final_split: {final_split}")
        
        strout=" " # setvtrgb BUG @linux/kbd/src/setvtrgb.c:144~154 :: rewind() after fgetc() won't work for stdin, hence the space
        for idx, channel in enumerate(final_split):
            if DBG: print(f"channel[{idx}]: {channel}")
            strout += f"{','.join([str(x) for x in channel])}\n"
        if DBG: print('strout=',strout)
        
        try:
            sp.check_output(['setvtrgb', '-'], input=strout, text=True)
        except:
            import traceback as tb
            import sys
            tb.print_exc()
            sys.exit(1)
        
        angle += ANGLE_STEP
        angle %= 360.0
        if DBG: print(f"angle={angle}")
        time.sleep(DELAY/2.0)

if __name__=="__main__":
    main()