[Melbourne-pm] Image Manipulation
scottp at dd.com.au
Fri Apr 28 07:06:41 PDT 2006
As part of my Gallery code I need a very minimal set of image
It has been wisely suggested to me that it is not a good idea just to
depend on something like Image::Magic. One reason for this is that
some implementations of a Gallery back end (eg: Flickr) do all the
work for you.
So I could have it that my implementations of a library (eg: my
example Simple, which works purely on files and directories) could
depend on the necessary code, eg: Image::Magick.
This is tricky though because it then means that the simplest of
classes requires the most complicated code, and I would like to have
the simple class, at least for testing.
A quick side track: For those of you who do not know, I am writing
"Gallery::" (name yet to be confirmed) which is an abstract Gallery
API that works with any backend. Think of it as the DBI for Galleries.
Then I was reading up on all of the library advantages and
Firstly, my requirements are fairly small, here is a simple list:
* resize - Resize an image, almost always scaled (proportional),
* height/width - I need it... get it for me.
* rotate - Only need to do CW/CCW 90 degree increments
* return objec handle (to library) - Nice to pass it back, since it
already exists, eg: if the user wants to do more in the native library.
So then I went through as many of the CPAN libraries as I could, and
here is a quick summary, mostly they include some code to do the
resize as a sample. The braces on the right indicate the features it
Image::Magick (height/width, resize, object)
my $im = Image::Magick->new;
# Note: Also returns height/width
GD (height/width, resize, object)
Ahhh too hard, use Image::Resize !
Image::Resize - GD wrapper (height/width, resize, object)
$image = Image::Resize->new('large.jpg');
$gd = $image->resize(250, 250);
# Note: Also returns height/width
Imager (height/width, resize, object)
$newimg = $img->copy();
$newimg = $img->scale(xpixels=>400);
$newimg = $img->scale(xpixels=>400, ypixels=>400);
Image::Epeg - JPEG only, but very fast (height/width, resize)
# Resize down only !
# Can set commments
my $epg = new Image::Epeg( "test.jpg" );
$epg->resize( 150, 150, MAINTAIN_ASPECT_RATIO );
$epg->write_file( "test_resized.jpg" );
GFL::Image (height/width, resize, object)
# Note: Very nice, but license issues (free, non-commercial)
$im -> load("test.png");
$im -> set( output => "jpeg", undolevel => 5);
$im -> resize (320, 200);
$im -> save("test.jpg");
Image::Imlib (height/width, resize, object)
my $image = Image::Imlib2->load("foo.png");
my $info = image_info("image.jpg");
my($w, $h) = dim($info);
Image::Filter - another GD wrapper (not enough)
So... down to where to from here...
Let me say that one of my requirements is to have little to no
requirements on large, especially C based (and thus compiled)
external modules. Sure, they are required to do resize (I am not
reinventing here) but if you don't resize, the library still works...
It seems I have a few options on where to go...
1) Hard code a few of the libraries in my own specific order. Try to
load them, on failure fall through to one that works, or report that
we need at least something. I note that many of the Gallery PHP
applications use this approach, or a static list of which modules are
2) Write a wrapper class inside Gallery to deal with the above,
allowing people to add a new backend without changing the other bits
of code. This also implies that the user would have the ability to
define which are supported/tried and in what order. This could speed
things up on a busy site - but the library would still automatically
try in case it doesn't know - allowing for a Zero configuration,
3) Write an external wrapper - yet another abstraction, just for the
most basic of functions - height, width, resize, rotate... Really the
same as 2 but make it more usable outside. A little harder to write,
new tests, module space etc.
My current thoughts is leaning in on 2.
3 worries me a little for two reasons: It is an unnecessary
abstraction - using the Simple driver of Gallery you can already
achieve what you would otherwise with 3, so just use Gallery (this is
a sort of); where would it go, it seems that people writing modules
such as "Image::Resize" have this sort of in mind, but have limited
to one function, and one backend.
So... over to you my active perl development team and friends. What
do you think I should do ?
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 186 bytes
Desc: This is a digitally signed message part
Url : http://mail.pm.org/pipermail/melbourne-pm/attachments/20060429/b0ce5032/attachment.bin
More information about the Melbourne-pm