PpmImagePlugin.py 文件源码

def _save(im, fp, filename):
    if im.mode == "1":
        rawmode, head = "1;I", b"P4"
    elif im.mode == "L":
        rawmode, head = "L", b"P5"
    elif im.mode == "I":
        if im.getextrema()[1] < 2**16:
            rawmode, head = "I;16B", b"P5"
        else:
            rawmode, head = "I;32B", b"P5"
    elif im.mode == "RGB":
        rawmode, head = "RGB", b"P6"
    elif im.mode == "RGBA":
        rawmode, head = "RGB", b"P6"
    else:
        raise IOError("cannot write mode %s as PPM" % im.mode)
    fp.write(head + ("\n%d %d\n" % im.size).encode('ascii'))
    if head == b"P6":
        fp.write(b"255\n")
    if head == b"P5":
        if rawmode == "L":
            fp.write(b"255\n")
        elif rawmode == "I;16B":
            fp.write(b"65535\n")
        elif rawmode == "I;32B":
            fp.write(b"2147483648\n")
    ImageFile._save(im, fp, [("raw", (0, 0)+im.size, 0, (rawmode, 0, 1))])

    # ALTERNATIVE: save via builtin debug function
    # im._dump(filename)

#
# --------------------------------------------------------------------