Image.py 文件源码

def _getscaleoffset(expr):
    stub = ["stub"]
    data = expr(_E(stub)).data
    try:
        (a, b, c) = data  # simplified syntax
        if (a is stub and b == "__mul__" and isinstance(c, numbers.Number)):
            return c, 0.0
        if a is stub and b == "__add__" and isinstance(c, numbers.Number):
            return 1.0, c
    except TypeError:
        pass
    try:
        ((a, b, c), d, e) = data  # full syntax
        if (a is stub and b == "__mul__" and isinstance(c, numbers.Number) and
                d == "__add__" and isinstance(e, numbers.Number)):
            return c, e
    except TypeError:
        pass
    raise ValueError("illegal expression")


# --------------------------------------------------------------------
# Implementation wrapper