affine_transformations.py

'''
I never understand affine transformations, which is why I made this little
script here.

basic docs:
    https://fonttools.readthedocs.io/en/latest/misc/transform.html

rf docs (explains how to convert normal operations (rotate, scale) to
affine transformations):
    https://doc.robofont.com/documentation/topics/transformations/

great interactive visualization (use the slider):
    https://bossmaths.com/matrices-4/

'''

f = CurrentFont()
g = CurrentGlyph()

transformations = [
    # horizontal scale
    # vertical shear
    # horizontal shear
    # vertical scale
    # x translate
    # y translate

    (1, 0, 0, 1, 0, 0),  # does nothing (100% scale)
    (2, 0, 0, 2, 0, 0),  # double size
    (1, 0, 0, 1, 100, 50),  # move by 100, 50
    (.5, 0, 0, .5, 0, 0),  # 50% proportional scale
    (0, 1, -1, 0, 0, 0),   # 90 degree rotation
    (1, 0, 0, .25, 0, 0),   # squooshed to 1/4 height
    (1, 0, 0, -1, 0, 0),   # mirrored on the x-axis
    (0, 1, 1, 0, 0, 0),   # diagonal flip
    (-1, 0, 0, -1, 0, 0),   # 180° rotation
    (0, 1, -1, 0, 0, 0),   # 270° rotation
    (1, 0, 0.2, 1, 0, 0),   # shear by 20% -- a kinda strong Italic
    (1, 1, 0, 1, 0, 0),   # vertical shear, horizontal handles turned 45°
]

if not g:
    print('please select a glyph')
else:
    for transformation in transformations:
        # give the transformed glyph a reasonable name, and insert it
        tr_name = repr(transformation).replace(' ', '')
        gname = f'{g.name}_{tr_name}'
        ng = g.copy()
        ng.name = gname
        ng.transformBy(transformation)
        f.insertGlyph(ng)

        # put the base glyph in the background
        background = f.getLayer('background')
        bg = g.copy()
        bg.name = gname
        background.insertGlyph(bg)