Re: OT? plpython2u

On 10/20/2016 12:03 PM, Nahum Castro wrote:
>
>
> 2016-10-20 13:06 GMT-05:00 Jonathan Rogers <jrogers@socialserve.com
> <mailto:jrogers@socialserve.com>>:
>
>     On 10/20/2016 01:14 PM, Nahum Castro wrote:
>     > Hello all.
>     >
>     > I need to process images on my database, they are stored on a bytea column.
>     >
>     > The process consist on scaling and I have done this so far:
>     >
>     > CREATE OR REPLACE FUNCTION  ajustar(randstring bytea)
>     > RETURNS bytea AS
>     > $$
>     >     import PIL
>     >     from PIL import Image
>     >     basewidth = 300
>     >     img = randstring
>     >     wpercent = (basewidth/float(img.size[0]))
>     >     hsize = int((float(img.size[1])*float(wpercent)))
>     >     img = img.resize((basewidth,hsize), PIL.Image.ANTIALIAS)
>     >
>     >     return img
>     > $$
>     >   LANGUAGE 'plpython2u' VOLATILE;
>
>     As you probably know, Postgres procedural languages are server-side
>     extensions and therefore have nothing to do with psycopg, which is a
>     client-side library.
>
> ​Thanks, but rather than help in plpython is how to pass the variable
> bytea from postgres to an image in python.
>
>
>     >
>     > The objective of this pl is read the bytea from the database, scale,
>     > then replace the scaled image in the database, but I don't know  what
>     > type use to pass to the variable img.
>
>     AFAICT, if you pass a bytea value to a plpythonu function, it will
>     receive a Python str object.
>
>
> ​That is where i get confused, what is stored in the db is in bytea, how
> I do to transform in a str?​

It is done for you:

https://www.postgresql.org/docs/9.5/static/plpython-data.html#AEN65498

"PostgreSQL bytea is converted to Python str in Python 2 and to bytes in
Python 3. In Python 2, the string should be treated as a byte sequence
without any character encoding.

When the PostgreSQL return type is bytea, the return value will be
converted to a string (Python 2) or bytes (Python 3) using the
respective Python built-ins, with the result being converted to bytea."


So something like this:

CREATE OR REPLACE FUNCTION public.ajustar(randstring bytea)
  RETURNS bytea
  LANGUAGE plpythonu
AS $function$
     from io import BytesIO
     import PIL
     from PIL import Image
     basewidth = 300
     mem_file = BytesIO()
     mem_file.write(randstring)
     img = Image.open(mem_file)
     wpercent = (basewidth/float(img.size[0]))
     hsize = int((float(img.size[1])*float(wpercent)))
     img = img.resize((basewidth,hsize), PIL.Image.ANTIALIAS)

     return img
$function$


postgres@test=# select ajustar(barcode) from pict_test where full_upc =
'744835000544';
                                                              ajustar


----------------------------------------------------------------------------------------------------------------------------------


\x3c50494c2e496d6167652e496d61676520696d616765206d6f64653d5247422073697a653d333030783230392061742030783746393343314532333635303e
(1 row)


barcode are small png's in this case.

>
>
>
>
>     >
>     > This is the query.
>     > update personal set foto=ajustar(encode(foto, 'hex')::bytea);
>
>     Why are you encoding the binary data into a textual representation? What
>     image format is stored in column "foto"? Depending on the format, you
>     probably want to use one of these constructors in function "ajustar":
>
>
> ​Sorry I forgot, all images are in jpeg​ format.
>
>
>
>     http://pillow.readthedocs.io/en/3.4.x/reference/Image.html?highlight=Image#PIL.Image.fromstring
>     <http://pillow.readthedocs.io/en/3.4.x/reference/Image.html?highlight=Image#PIL.Image.fromstring>
>
>     http://pillow.readthedocs.io/en/3.4.x/reference/Image.html?highlight=Image#PIL.Image.open
>     <http://pillow.readthedocs.io/en/3.4.x/reference/Image.html?highlight=Image#PIL.Image.open>
>
>
> ​Again thanks.​
> Nahum
>
>
>
>     --
>     Jonathan Rogers
>     Socialserve.com by Emphasys Software
>     jrogers@emphasys-software.com <mailto:jrogers@emphasys-software.com>
>
>     --
>     Jonathan Rogers
>     Socialserve.com by Emphasys Software
>     jrogers@emphasys-software.com <mailto:jrogers@emphasys-software.com>
>
>
>     --
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>
>
>
>
> --
> *Nahum Castro González*
> Blvd. Perdigón 214, Brisas del Lago.
> CP 37207
> León, Guanajuato, México
> Tel (477)1950304
> Cel (477)1274694


--
Adrian Klaver
adrian.klaver@aklaver.com