pimoroni-pico/micropython/examples/pico_display/rainbow.py

# This example borrows a CircuitPython hsv_to_rgb function to cycle through some rainbows on Pico Display's screen and RGB LED . If you're into rainbows, HSV (Hue, Saturation, Value) is very useful!

import utime
import st7789
from pimoroni import RGBLED

display = st7789.ST7789(st7789.DISPLAY_PICO_DISPLAY, rotate=0)
display.set_backlight(0.8)
display.set_palette_mode(st7789.PALETTE_USER)

WIDTH, HEIGHT = display.get_bounds()

led = RGBLED(6, 7, 8)


# From CPython Lib/colorsys.py
def hsv_to_rgb(h, s, v):
    if s == 0.0:
        return v, v, v
    i = int(h * 6.0)
    f = (h * 6.0) - i
    p = v * (1.0 - s)
    q = v * (1.0 - s * f)
    t = v * (1.0 - s * (1.0 - f))
    i = 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


h = 0

BLACK = display.create_pen(0, 0, 0)
RAINBOW = BLACK + 1  # Put RAINBOW right after BLACK in the palette


while True:
    h += 1
    r, g, b = [int(255 * c) for c in hsv_to_rgb(h / 360.0, 1.0, 1.0)]  # rainbow magic
    led.set_rgb(r, g, b)      # Set LED to a converted HSV value
    display.set_palette(RAINBOW, st7789.RGB565(r, g, b)) # Create pen with converted HSV value
    display.set_pen(RAINBOW)  # Set pen
    display.clear()           # Fill the screen with the colour
    display.set_pen(BLACK)    # Set pen to black
    display.text("pico disco!", 10, 10, 240, 6)  # Add some text
    display.update()          # Update the display
    utime.sleep(1.0 / 60)