DrawBot script to create joyful GIF animations of interpolated glyphs

drawbot_interpolate_glyph_gif.py

'''
Type@Cooper West, June 2018
Contribution to Andy Clymer's "Expanding a Type Family" workshop

Script to create joyful GIF animations of interpolated glyphs,
either colorful or black & white.

'''

from fontTools.pens.cocoaPen import CocoaPen
import os
import colorsys
from math import sin, pi
from fontParts.nonelab import RFont, RGlyph
# maybe fontshell?

doc_height = doc_width = 1200


def draw_glyph(glyph):
    cpen = CocoaPen(glyph.getParent())
    glyph.draw(cpen)
    drawPath(cpen.path)


font_light = RFont(os.path.expanduser('~/Desktop/light.ufo'))
font_heavy = RFont(os.path.expanduser('~/Desktop/heavy.ufo'))

glyph_name = 'a'
interpolation_steps = 20

hue_a = randint(0, 255)
hue_b = randint(0, 255)
hue_gamut = hue_b - hue_a

glyph_light = font_light[glyph_name]
glyph_heavy = font_heavy[glyph_name]

interpolation_steps = 20

for frame in range(interpolation_steps):

    # calculate time value t
    t = frame / interpolation_steps
    # calculate an angle in radians based on t, from which we can
    # deduce a sine wave
    angle = 2 * pi * t
    factor = sin(angle)

    # interpolate the glyph by the interpolation factor
    interpolated_glyph = RGlyph()
    interpolated_glyph.interpolate(
        0.5 + factor / 2, glyph_light, glyph_heavy)
    interpolated_glyph_alt = RGlyph()

    # calculate a hue based on the interpolation factor
    hue = hue_a + (hue_gamut / 2 * factor)
    color = colorsys.hls_to_rgb(hue / 255, 0.5, 1)

    # glyph measurements for scaling
    bbox_height = interpolated_glyph.bounds[3] - interpolated_glyph.bounds[1]
    bbox_top = interpolated_glyph.bounds[3]
    overshoot = interpolated_glyph.bounds[1]

    # calculate scale factor so the glyph fits optimally into our square
    margin = 20
    scale_factor = (doc_height - (2 * margin)) / bbox_height

    # draw the pages
    newPage(doc_height, doc_width)
    frameDuration(1 / interpolation_steps * 2)

    # background fill
    fill(0)
    rect(0, 0, width(), height())

    # letter fill
    fill(*color)  # colorful
    # fill(1)  # white

    # calculate space around the glyph (so we can center it)
    padding = (width() - 2 * margin - interpolated_glyph.width) / 2
    save()
    # scale and translate the glyph, and finally dtaw it
    scale(scale_factor, scale_factor, center=(width()/2, 0))
    translate(margin, margin - overshoot / 2)
    translate(padding, 0)
    draw_glyph(interpolated_glyph)
    restore()

# save as GIF
saveImage('~/Desktop/interpolation.gif')
# save as movie
# saveImage('~/Desktop/interpolation.mov')