[Numpy-discussion] numarray types and PIL modes, revisited
Edward C. Jones
edcjones at erols.com
Wed Jan 1 20:29:44 EST 2003
Perry Greenfield wrote:
> Edward Jones writes:
> > I write code using both PIL and numarray. PIL uses strings for
> > modes and numarray uses (optionally) strings as typecodes. This
> > causes problems. One fix is to emit a DeprecationWarning when
> > string typecodes are used. Two functions are needed:
> > StringTypeWarningOn and StringTypeWarningOff. The default
> > should be to ignore this warning.
> I'm not sure I understand. Can you give me an example of problem
> code or usage? It sounds like you are trying to test the types of
> PIL and numarray objects in a generic sense. But I'd understand
> better if you could show an example.
That's what I was thinking (incorrectly). But I don't need to directly
compare PIL modes with numarray types.
My code never tries to deduce whether an array is a numarray or a PIL
image from just the natype_or_mode. A module name (MODULE.NUMARRY,
MODULE.PIL) must also be given. I do things this way because I might
want to include other array/image systems. In an earlier version, I had
a MODULE.IPL for the Intel Image Processing Library.
The code also implements a policy of forbidding string types.
So now all I can say is:
1. UInt8 == 'X' should not raise an exception. It should return False.
3. There needs to be a function that returns True iff arg is a numarry
type (UInt8, "UInt8", "b", ...).
from numerictypes import typeDict
return isinstance(rep, NumericType) or typeDict.has_key(rep)
Here is a typical piece of code. "module" can be MODULE.PIL or
"""General image casting function. Changes the C type of the pixels.
Information can be lost. The "Convert" functions call C casting
functions that clip the values, For example, if the input is a UInt16
and the output is a Int16, any input value greater than 32767 becomes 32767.
def ArrayToArrayCast(arrin, module, natype_or_mode):
"""Converts one array into another. Results are clipped."""
pars = Parameters(arrin)
if pars.module == module == MODULE.PIL and \
pars.mode == natype_or_mode:
if pars.module == module == MODULE.NUMARRAY and \
if pars.module == MODULE.NUMARRAY and module == MODULE.NUMARRAY:
return NA_To_NA_Convert(arrin, natype_or_mode)
if pars.module == MODULE.PIL and module == MODULE.PIL:
return PIL_To_PIL_Convert(arrin, natype_or_mode)
if pars.module == MODULE.NUMARRAY and module == MODULE.PIL:
return NA_To_PIL_Convert(arrin, natype_or_mode)
if pars.module == MODULE.PIL and module == MODULE.NUMARRAY:
return PIL_To_NA_Convert(arrin, natype_or_mode)
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