Export PNG with transparent background

export_single_png.py

# using py5 imported mode (https://py5coding.org to learn more)

def setup():
    size(600, 600)  # drawing size
    output_canvas = create_graphics(width, height)
    background(255, 0, 0) # you can turn this off, this won't be recorded!
    begin_record(output_canvas) # starts recording
    # output_canvas.clear()  # clears pixels (not necessary in this case)
    color_mode(HSB)  # this needs to be inside the recording!
    no_stroke()  # same as with the color_mode, has to be brought here
    w = 60
    for j in range(10):    
        y = w / 2 + j * w
        for i in range(10):   # 0, 1, 2, ... 9
            x = w / 2 + i * w
            d = random(10, w)
            fill(d * 3, 255, 255)
            circle(x + random(-15, 15),
                   y + random(-15, 15), d)
    end_record()  # end recording
    output_canvas.save(f'out.png', drop_alpha=False)