JpegImagePlugin.py 文件源码

def DQT(self, marker):
    #
    # Define quantization table.  Support baseline 8-bit tables
    # only.  Note that there might be more than one table in
    # each marker.

    # FIXME: The quantization tables can be used to estimate the
    # compression quality.

    n = i16(self.fp.read(2))-2
    s = ImageFile._safe_read(self.fp, n)
    while len(s):
        if len(s) < 65:
            raise SyntaxError("bad quantization table marker")
        v = i8(s[0])
        if v//16 == 0:
            self.quantization[v & 15] = array.array("b", s[1:65])
            s = s[65:]
        else:
            return  # FIXME: add code to read 16-bit tables!
            # raise SyntaxError, "bad quantization table element size"


#
# JPEG marker table