Feature request: Check if glyph exists in font

[glebm]

Using the freetype-py library, I can check if a glyph exists in a font like this:

ft_font = freetype.Face(font_path)
exists = ft_font.get_char_index(0x41) != 0

It'd be nice to have this functionality exposed in Pillow as well.

[radarhere]

Are you interested in immediate solutions at all? I suspect no, since using freetype-py would be a viable immediate solution.

Anyway, for an immediate Pillow-only solution, I would suggest comparing the character's output to the output of the replacement character, U+FFFD.

def checkIfCharacterIsMissing(fontPath, text):
    font = ImageFont.truetype(fontPath)

    w, h = font.getbbox(text)[2:]
    im = Image.new("L", (w, h), 255)
    draw = ImageDraw.Draw(im)
    draw.text((0, 0), text, font=font)

    w, h = font.getbbox("\ufffd")[2:]
    if im.size != (w, h):
        return False
    im2 = Image.new("L", (w, h), 255)
    draw = ImageDraw.Draw(im2)
    draw.text((0, 0), "\ufffd", font=font)

    return im.tobytes() == im2.tobytes()

[glebm]

I'm using freetype-py for this at the moment, it'd just be nice to be able to do everything via pillow.

https://github.com/diasurgical/devilutionx-font-converter/blob/ac0f0e48bd690ace783c6c1b16e52b569e46f551/src/devilutionx_font_converter/convert.py#L178-L183

It'd also be nice if glyph properties (such as horiAdvance) were exposed via pillow.

[radarhere]

I can understand why a Pillow user might want to know if a glyph existed or not - so you can avoid drawing it with Pillow.

I'm less convinced that knowing the glyph properties directly fits into Pillow's overall goal. Could you explain to me how it would help a Pillow user generate an image? If you would like it in order to convert fonts, that indeed sounds like a job better suited to freetype-py.

[glebm]

I'm using pillow to generate textured bitmap fonts for a game from OTF fonts.

For later rendering in-game, the width of each rasterized glyph should be its horizontal advance, which can be larger than the glyph itself. Knowing the horizontal advance lets us know the image width.

[radarhere]

If you're just talking about horiAdvance, then that should be the value returned by getlength() for horizontal directions.

https://github.com/python-pillow/Pillow/blob/9d39fe6adac233ccd26ba20bff9adda53a1ec89d/src/_imagingft.c#L486 https://github.com/python-pillow/Pillow/blob/9d39fe6adac233ccd26ba20bff9adda53a1ec89d/src/_imagingft.c#L555

[glebm]

Ah, yeah, that indeed looks like exactly what I need. Thanks Andrew!

[radarhere]

The PR has received some feedback - https://github.com/python-pillow/Pillow/pull/9160#issuecomment-3405200697

I'm on the fence with this. It feels outside the core focus of Pillow, and it's not too tricky to do this with Pillow in Python:

https://github.com/python-pillow/Pillow/issues/9158#issuecomment-3194350459

Plus it's a even easier with a dedicated FreeType library:

https://github.com/python-pillow/Pillow/issues/9158#issue-3328268124

Any thoughts?