Graphics routine for Pimoroni Pico Explorer

# Graphics routines for Pimoroni Pico Explorer
#      and Raspberry Pi Pico
# Tony Goodhew (arduinolink(AT)gmail.com)
# 25 January 2021
import picoexplorer as display
import time
import math
width = display.get_width()
height = display.get_height()
display_buffer = bytearray(width * height * 2)
display.init(display_buffer)

# Set the backlight to 90%
display.set_backlight(0.9)

# Define special 5x8 characters - 8 bytes each - 0...7
# Bytes top to bottom, 5 least significant bits only
smiley = [0x00,0x0A,0x00,0x04,0x11,0x0E,0x00,0x00]
sad = [0x00,0x0A,0x00,0x04,0x00,0x0E,0x11,0x00]
heart = [0,0,0,10,31,14,4,0]
b_heart = [0,10,31,0,0,14,4,0]
up_arrow =[0,4,14,21,4,4,0,0]
down_arrow = [0,4,4,21,14,4,0,0]
bits = [128,64,32,16,8,4,2,1]  # Powers of 2

def mychar(xpos, ypos, pattern):  # Print defined character
    for line in range(8):       # 5x8 characters
        for ii in range(5):     # Low value bits only
            i = ii + 3
            dot = pattern[line] & bits[i]  # Extract bit
            if dot:  # Only print WHITE dots
                display.pixel(xpos+i*2, ypos+line*2)
                display.pixel(xpos+i*2+1, ypos+line*2)
                display.pixel(xpos+i*2, ypos+line*2+1)
                display.pixel(xpos+i*2+1, ypos+line*2+1)

def horiz(l,t,r):  # left, top, right
    n = r-l+1        # Horizontal line
    for i in range(n):
        display.pixel(l + i, t )

def vert(l,t,b):   # left, top, bottom
    n = b-t+1        # Vertical line
    for i in range(n):
        display.pixel(l, t+i)

def box(l,t,r,b):  # left, top, right, bottom
    horiz(l,t,r)   # Empty rectangle
    horiz(l,b,r)
    vert(l,t,b)
    vert(r,t,b)

def line(x,y,xx,yy): # (x,y) to (xx,yy)
    if x > xx:
        t = x  # Swap co-ordinates if necessary
        x = xx
        xx = t
        t = y
        y = yy
        yy = t
    if xx-x == 0:  # Avoid div by zero if vertical
        vert(x,min(y,yy),max(y,yy))
    else:          # Draw line one dot at a time L to R
        n=xx-x+1
        grad = float((yy-y)/(xx-x))  # Calculate gradient
        for i in range(n):
            y3 = y + int(grad * i)
            display.pixel(x+i,y3)  # One dot at a time

def ring(cx,cy,rr): # Centre and radius
    display.circle(cx,cy,rr)
    display.set_pen(0,0,0) # background colour
    display.circle(cx,cy,rr-1)

def ring2(cx,cy,r):   # Centre (x,y), radius
    for angle in range(0, 90, 2):  # 0 to 90 degrees in 2s
        y3=int(r*math.sin(math.radians(angle)))
        x3=int(r*math.cos(math.radians(angle)))
        display.pixel(cx-x3,cy+y3)  # 4 quadrants
        display.pixel(cx-x3,cy-y3)
        display.pixel(cx+x3,cy+y3)
        display.pixel(cx+x3,cy-y3)

def show(t): # Update display and short pause
    display.update()
    time.sleep(t)

# ===== Main ======
display.set_pen(255,255,0)
line(10,10,100,100)
show(1)
display.set_pen(255,0,255)
line(10,100,100,10)
show(1)
display.set_pen(0,255,255)
box(0,105,100,205)
show(1)
display.set_pen(255,0,0)
ring(160,50,50)
show(1)
display.set_pen(0,0,255)
ring2(160,160,50)
show(1)
display.text("Tony Goodhew", 15, 220, 240,3)
display.update()
mychar(20, 130, up_arrow)    # Defined characters
mychar(40, 130, smiley)
mychar(60, 130, heart)
mychar(20, 160, down_arrow)
mychar(40, 160, sad)
mychar(60, 160, b_heart)
display.update()