An interesting Python script from Planet Python for creating text watermarks in image files.

 
#!/usr/bin/python
from PIL import Image, ImageDraw, ImageFont
from math import atan, degrees
import sys
import os
FONT = "C:\\WINDOWS\\Fonts\\BKANT.TTF"
def main(filename, text, outfilename):
    img = Image.open(filename).convert("RGB")
    watermark = Image.new("RGBA", (img.size[0], img.size[1]))
    draw = ImageDraw.ImageDraw(watermark, "RGBA")
    size = 0
    while True:
        size += 1
        nextfont = ImageFont.truetype(FONT, size)
        nexttextwidth, nexttextheight = nextfont.getsize(text)
        if nexttextwidth+nexttextheight/3 > watermark.size[0]:
            break
        font = nextfont
        textwidth, textheight = nexttextwidth, nexttextheight
    draw.setfont(font)
    #draw.text(((watermark.size[0]-textwidth)/2,
    #           (watermark.size[1]-textheight)/2), text) #Höhe = Mitte
    draw.text(((watermark.size[0]-textwidth)/2,
               (watermark.size[1]-textheight)), text)
    #Diagonal Zeichnen:
    #watermark = watermark.rotate(degrees(atan(float(img.size[1])/img.size[0])),
                                 #Image.BICUBIC)
    mask = watermark.convert("L").point(lambda x: min(x, 55))
    watermark.putalpha(mask)
    img.paste(watermark, None, watermark)
    img.save(outfilename)
if __name__ == "__main__":
    if len(sys.argv) != 4:
        sys.exit("Usage: %s <input-image> <text> <output-image>"
                 % os.path.basename(sys.argv[0]))
    main(*sys.argv[1:])