screen.py

import colorsys
import logging

import ST7735
from PIL import Image, ImageDraw, ImageFont
from fonts.ttf import RobotoMedium as UserFont

logging.basicConfig(
    format='%(asctime)s.%(msecs)03d %(levelname)-8s %(message)s',
    level=logging.INFO,
    datefmt='%Y-%m-%d %H:%M:%S')

logging.info("""lcd.py - Hello, World! example on the 0.96" LCD.
Press Ctrl+C to exit!
""")

# Create LCD class instance.
disp = ST7735.ST7735(
    port=0,
    cs=1,
    dc=9,
    backlight=12,
    rotation=270,
    spi_speed_hz=10000000
)

# Initialize display.
disp.begin()

# Width and height to calculate text position.
WIDTH = disp.width
HEIGHT = disp.height

# New canvas to draw on.
img = Image.new('RGB', (WIDTH, HEIGHT), color=(0, 0, 0))
draw = ImageDraw.Draw(img)

# Text settings.
font_size = 20
font = ImageFont.truetype(UserFont, font_size)
text_colour = (255, 255, 255)
back_colour = (0, 170, 170)

top_pos = 25

initial_message = "Well hello there!"
size_x, size_y = draw.textsize(initial_message, font)

# Calculate text position
x = (WIDTH - size_x) / 2
y = (HEIGHT / 2) - (size_y / 2)

# Draw background rectangle and write text.
draw.rectangle((0, 0, 160, 80), back_colour)
draw.text((x, y), initial_message, font=font, fill=text_colour)
disp.display(img)

values = {}


def display_text(variable, data, unit):
    # Maintain length of list
    values[variable] = values.get(variable, [1] * WIDTH)[1:] + [data]
    # Scale the values for the variable between 0 and 1
    colours = [(v - min(values[variable]) + 1) / (max(values[variable])
                                                  - min(values[variable]) + 1) for v in values[variable]]
    # Format the variable name and value
    message = "{}: {:.1f} {}".format(variable[:4], data, unit)
    draw.rectangle((0, 0, WIDTH, HEIGHT), (255, 255, 255))
    for i in range(len(colours)):
        # Convert the values to colours from red to blue
        colour = (1.0 - colours[i]) * 0.6
        r, g, b = [int(x * 255.0) for x in colorsys.hsv_to_rgb(colour,
                                                               1.0, 1.0)]
        # Draw a 1-pixel wide rectangle of colour
        draw.rectangle((i, top_pos, i+1, HEIGHT), (r, g, b))
        # Draw a line graph in black
        line_y = HEIGHT - (top_pos + (colours[i] * (HEIGHT - top_pos))) \
                 + top_pos
        draw.rectangle((i, line_y, i+1, line_y+1), (0, 0, 0))
    # Write the text at the top in black
    draw.text((0, 0), message, font=font, fill=(0, 0, 0))
    disp.display(img)