Yes that could be useful!
I was playing around with
"Wand" which is an ImageMagick binding for Python. It offers a "get_font_metrics" which returns something like:
Code:
FontMetrics(character_width=35.0, character_height=35.0, ascender=35.0, descender=-13.0, text_width=628.0, text_height=618.0,
maximum_horizontal_advance=35.0, x1=5.5, y1=16.671875, x2=12.671875, y2=25.0, x=628.0, y=0.0)
Probably overkill for subtitling needs, but it is helpful.