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John Cupitt 2017-09-25 13:12:23 +01:00
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<refpurpose>Writing bindings for libvips</refpurpose> <refpurpose>Writing bindings for libvips</refpurpose>
</refnamediv> </refnamediv>
There are full libvips bindings for quite a few languages now: C, C++, Ruby, There are full libvips bindings for quite a few environments now: C, C++,
PHP, Python and JavaScript. command-line, Ruby, PHP, Python and JavaScript (node).
This chapter runs through the four main styles that have been found to work This chapter runs through the four main styles that have been found to work
well. If you want to write a new binding, one of these should be close well. If you want to write a new binding, one of these should be close
@ -182,21 +182,17 @@ it's as simple as:
from gi.repository import Vips from gi.repository import Vips
``` ```
libvips used in this way is likely to be rather bare-bones. For Python, we You can now use all of the libvips introspection machinery, as noted above.
wrote a set of overrides which layer a more Pythonesque interface on top
of the one provided for libvips by pygobject. These overrides are simply
a set of Python classes.
To call a vips operation, you'll need to make a new operation with Unfortunately g-o-i has some strong disadvantages. It is not very portable,
vips_operation_new() (all it does is look up the operation by name since you will need a g-o-i layer for whatever platform you are targetting,
with vips_type_find(), then call g_object_new() for you), then use it does not cross-compile well since typelibs include a lot of very-low level
vips_argument_map() and friends to loop over the operation's arguments setting data (such as exact structure layouts), and installation for your users is
them. Once you have set all arguments, use vips_cache_operation_build() likely to be tricky.
to look up the operation in the cache and either build or dup it. If
something goes wrong, you'll need to use vips_object_unref_outputs() and If you have a choice, I would recommend simply using FFI.
g_object_unref() to free the partially-built object. The Python binding uses
this technique to implement a function which can call any vips operation, # Documentation
turning optional vips arguments into Python keyword arguments.
You can generate searchable docs from a <code>.gir</code> (the thing that You can generate searchable docs from a <code>.gir</code> (the thing that
is built from scanning libvips and which in turn turn the typelib is is built from scanning libvips and which in turn turn the typelib is