I use exotic fonts and sometimes the text side-cut corners.
How it fix?

My code:

font = ImageFont.truetype(fontfile, fontsize)
        text_width, text_height = font.getsize(text)
        img = Image.new('RGBA', (text_width, text_height))
        draw = ImageDraw.Draw(img)
        draw.text((0, 0), text, font=font, fill=(0, 0, 0))

I found no Image module in Tkinter, WxPython, or Qt, so just a wild guess would be that you are not allowing for the thickness of outside lines. If you are drawing a right angle, the insides would touch but there would be a gap from outside to outside.