Re: OT? plpython2u

On 10/20/2016 12:03 PM, Nahum Castro wrote:
>
>
> 2016-10-20 13:06 GMT-05:00 Jonathan Rogers <jrogers(at)socialserve(dot)com
> <mailto:jrogers(at)socialserve(dot)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(at)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(at)emphasys-software(dot)com <mailto:jrogers(at)emphasys-software(dot)com>
>
> --
> Jonathan Rogers
> Socialserve.com by Emphasys Software
> jrogers(at)emphasys-software(dot)com <mailto:jrogers(at)emphasys-software(dot)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(dot)klaver(at)aklaver(dot)com