Re: OT? plpython2u

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.

>
> 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.

>
> 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":

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

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Jonathan Rogers
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jrogers(at)emphasys-software(dot)com