python image thumbnail generator?

[Chris Dewin]

Hi. I run a website for my band, and the other guys want an image gallery.

I'm thinking it would be nice and easy, if we could just upload a jpg into
a dir called "gallery/". When the client clicks the "gallery" link, a
cgi script could search the gallery/ dir, and create thumbnails of any
jpeg images that don't already have a thumbnail associated with them. The
script could then generate a page of clickable thumbnails.

A few questions:

(1) Can this be done with python? If so, what module do I need to look up?

(2) If it can't be done with python, is there some small utility that will
do it for me? Something I could easily install locally in my own
"public_html" dir on my website?

(3) Is this the sort of thing which, if done regularly, would hog far far
too much of my webhosts system resources?

(4) Am I talking about re inventing the wheel?

[Paul Rubin]

"Chris Dewin" <ch***@wintergreen.in> writes:

(1) Can this be done with python? If so, what module do I need to look up?

You could do it with PIL, or run jpegtran in an external process.
jpegtran may be easier.

[Mike C. Fletcher]

Chris Dewin wrote:

Hi. I run a website for my band, and the other guys want an image gallery.

I'm thinking it would be nice and easy, if we could just upload a jpg into
a dir called "gallery/". When the client clicks the "gallery" link, a
cgi script could search the gallery/ dir, and create thumbnails of any
jpeg images that don't already have a thumbnail associated with them. The
script could then generate a page of clickable thumbnails.

A few questions:

(1) Can this be done with python? If so, what module do I need to look up?

PIL can certainly handle the functionality.
(2) If it can't be done with python, is there some small utility that will
do it for me? Something I could easily install locally in my own
"public_html" dir on my website?

The core function looks something like this:

import Image # this is PIL

def getThumbnail( filename, size = (32,32) ):
'''Get a thumbnail image of filename'''
image = Image.open(filename)
rx, ry = image.size[0]/float(size[0]), image.size[1]/float(size[1])
if rx > ry:
resize = int(size[0]), int(round(image.size[1]*(1.0/rx), 0))
else:
resize = int(round(image.size[0]*(1.0/ry), 0)), int(size[1])
image = image.resize( resize, Image.BILINEAR )
newimage = Image.new( 'RGB', size, )
x,y = image.size
newimage.paste(
image, ((size[0]-x)/2, (size[1]-y)/2),
)
return newimage

then you call newImage.save( filename, format ) to save the result.
(3) Is this the sort of thing which, if done regularly, would hog far far
too much of my webhosts system resources?

As long as you *only* generate images for sources that don't yet have
(or are newer than) their thumbnail you should be fine.
(4) Am I talking about re inventing the wheel?

Probably. ZPhotoSlides (a Zope product) provides thumnailing,
slideshows and the like, probably closer to what you'd want for this
kind of application. You'll probably find other non-Zope versions as well.

Good luck,
Mike

--
________________________________________________
Mike C. Fletcher
Designer, VR Plumber, Coder
http://www.vrplumber.com
http://blog.vrplumber.com

[Wouter van Ooijen]

>I'm thinking it would be nice and easy, if we could just upload a jpg into

a dir called "gallery/". When the client clicks the "gallery" link, a
cgi script could search the gallery/ dir, and create thumbnails of any
jpeg images that don't already have a thumbnail associated with them. The
script could then generate a page of clickable thumbnails.

I dunno about the scripting aspect, but I use Python to generate my
website, I already had the images (of the products I sell). I used PIL
to generate thumbnails of the images. I think it took 2 or 3 lines of
Python - that is: for me. PIL is of course a bit more.


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
Webshop for PICs and other electronics
http://www.voti.nl/hvu
Teacher electronics and informatics

[Terry Hancock]

On Saturday 27 August 2005 09:06 pm, Chris Dewin wrote:

I'm thinking it would be nice and easy, if we could just upload a jpg into
a dir called "gallery/". When the client clicks the "gallery" link, a
cgi script could search the gallery/ dir, and create thumbnails of any
jpeg images that don't already have a thumbnail associated with them. The
script could then generate a page of clickable thumbnails.

This is trivial to do with Zope. I wrote a "VarImage" product for it
that will do the image manipulation you want handily. I never really
created a "gallery" product for it because it's so trivial to do with a
regular Zope folder and a couple of scripts, but I would be happy to
share my Gallery template with you if your interested.

The current version of VarImage even implements things like HTTP_REFERER
blocking (or watermarking if you prefer), to discourage remote-linking
of your images, etc.

An online example can be seen here: http://narya.net/Gallery

Not sure about CGI methods of doing it, though.
--
Terry Hancock ( hancock at anansispaceworks.com )
Anansi Spaceworks http://www.anansispaceworks.com

[Fredrik Lundh]

Paul Rubin wrote

(1) Can this be done with python? If so, what module do I need to look
up?

You could do it with PIL, or run jpegtran in an external process.
jpegtran may be easier.

eh? are you sure you know what jpegtran does?

JPEGTRAN(1)
JPEGTRAN(1)

NAME
jpegtran - lossless transformation of JPEG files

SYNOPSIS
jpegtran [ options ] [ filename ]

DESCRIPTION
jpegtran performs various useful transformations of JPEG files. It
can
translate the coded representation from one variant of JPEG to
another,
for example from baseline JPEG to progressive JPEG or vice versa.
It
can also perform some rearrangements of the image data, for
example
turning an image from landscape to portrait format by rotation.

jpegtran works by rearranging the compressed data (DCT
coefficients),
without ever fully decoding the image /.../

</F>

[Fredrik Lundh]

Mike C. Fletcher wrote:

The core function looks something like this:

import Image # this is PIL

def getThumbnail( filename, size = (32,32) ):
'''Get a thumbnail image of filename'''
image = Image.open(filename)
rx, ry = image.size[0]/float(size[0]), image.size[1]/float(size[1])
if rx > ry:
resize = int(size[0]), int(round(image.size[1]*(1.0/rx), 0))
else:
resize = int(round(image.size[0]*(1.0/ry), 0)), int(size[1])
image = image.resize( resize, Image.BILINEAR )

footnote: if you're creating thumbnails from JPEG or PhotoCD
images, using the "thumbnail" method can be a lot more efficient
(unlike resize, it tweaks the codec so it doesn't have to load the
entire full-sized image).

footnote 2: Image.ANTIALIAS is slower, but tends to give a
much better result than Image.BILINEAR, especiall for "noisy"
images.

</F>

[Paul Rubin]

"Fredrik Lundh" <fr*****@pythonware.com> writes:

You could do it with PIL, or run jpegtran in an external process.
jpegtran may be easier.

eh? are you sure you know what jpegtran does?

JPEGTRAN(1)

Whoops, sorry, right, jpegtran is for rotating the images. I meant:
use a pipeline like

djpeg -scale 1/4 | cjpeg

That's how I usually do it. Main disadvantage is the scale factor has
to be 1/2, 1/4, 1/8, etc., not arbitrary amounts like 0.3456.

[Damjan]

Chris Dewin wrote:

Hi. I run a website for my band, and the other guys want an image gallery.

I'm thinking it would be nice and easy, if we could just upload a jpg into
a dir called "gallery/". When the client clicks the "gallery" link, a
cgi script could search the gallery/ dir, and create thumbnails of any
jpeg images that don't already have a thumbnail associated with them. The
script could then generate a page of clickable thumbnails.

Once I made an example mod_python handler, that resized images on the fly.
For example:
http://server/folder/image.jpg - would give you the original image, served
directly by apache without any performance hit.

http://server/folder/image.jpg?thumbnail - would resize the picture (and
cache the result on disk) and return that, on a second request it would
return the cached image very fast by calling an apache.send_file function.

see
http://www.modpython.org/pipermail/m...er/016471.html

--
damjan