spirograph fun w/ bitmapfilter in CircuitPython

bitmapfilter_play2_code.py

# bitmapfilter_play2_code.py -- spirograph fun w/ bitmapfilter
# 1 Apr 2024 - @todbot / Tod Kurt
import time, math, random
import board
import rainbowio
import vectorio
import displayio
import bitmaptools
import bitmapfilter

display = board.DISPLAY
display.auto_refresh = False
dw,dh = display.width, display.height
cx,cy = dw//2, dh//2
display.root_group = displayio.Group()

bitmap = displayio.Bitmap(dw, dh, 65535)
pixel_shader = displayio.ColorConverter(input_colorspace=displayio.Colorspace.RGB565_SWAPPED)
tile_grid = displayio.TileGrid(bitmap, pixel_shader=pixel_shader)
display.root_group.append(tile_grid)

color_converter = displayio.ColorConverter(input_colorspace=displayio.Colorspace.RGB888)
def swap(v):
    """swap high & low bytes of 16-bit number, since RGB565_SWAPPED"""
    return ((v & 0xff) << 8) | ((v >> 8) & 0xff)
def to_bitmap_color(c):
    """convert RGB888 to RGB565_SWAPPED, surely there's a better way for this, gotta chat w/jepler"""
    return swap(color_converter.convert(c))
       
def make_spirograph(a,b,h, dt=0.05, colr=0xffff):
    """ from: https://samjbrenner.com/notes/processing-spirograph/"""
    t = 0
    ot = dt
    od = a*ot
    ab = a-b
    oxpos = int( ab*math.cos(ot) + h*math.cos(od))
    oypos = int( ab*math.sin(ot) + h*math.sin(od))
    while t < 6.28:
        d = a*t
        xpos = int( ab*math.cos(t) + h*math.cos(d))
        ypos = int( ab*math.sin(t) + h*math.sin(d))
        bitmaptools.draw_line(bitmap, cx+oxpos, cy+oypos, cx+xpos, cy+ypos, colr)
        ot, od = t, d  # save last angle and positions
        oxpos, oypos = xpos, ypos
        t += dt

a = 30  # spirograph parameter
b = 50  # spirograph parameter
h = 70  # spirograph parameter
dim  = bitmapfilter.ChannelScale(0.75, 0.75, 0.75)
last_time = 0
tic = 100  # position in phase space, arbitrary starting point

while True:
    tic += 0.01
    print("%.2f spiro! %3.2f %.2f, %.2f, %.2f" %(time.monotonic(), tic, a,b,h))
    a = 100 + 50 * math.sin(tic/5)  # evolve our spirograph settings
    h = 50 + 50 * math.sin(tic*3)   # evolve our spirograph settings
    colr = to_bitmap_color(rainbowio.colorwheel(time.monotonic()*15))

    make_spirograph( a, b, h, dt=0.03, colr=colr )
    
    if time.monotonic() - last_time > 0.1:
        last_time = time.monotonic()
        tile_grid.bitmap = bitmapfilter.mix(bitmap, dim) 
    display.refresh()

video demo: https://mastodon.social/@todbot/112198624310787505