NAME¶
Imager::API - Imager's C API - introduction.
SYNOPSIS¶
#include "imext.h"
#include "imperl.h"
DEFINE_IMAGER_CALLBACKS;
MODULE = Your::Module PACKAGE = Your::Module
...
BOOT:
/* any release with the API */
PERL_INITIALIZE_IMAGER_CALLBACKS;
/* preferred from Imager 0.91 */
PERL_INITIALIZE_IMAGER_CALLBACKS_NAME("My::Module");
DESCRIPTION¶
The API allows you to access Imager functions at the C level from XS and from
Inline::C.
The intent is to allow users to:
- •
- write C code that does Imager operations the user might do
from Perl, but faster, for example, the Imager::CountColor example.
- •
- write C code that implements an application specific
version of some core Imager object, for example, Imager::SDL.
- •
- write C code that hooks into Imager's existing methods,
such as filter or file format handlers.
See Imager::Inline for information on using Imager's Inline::C support.
Beware¶
- •
- don't return an object you received as a parameter - this
will cause the object to be freed twice.
Types¶
The API makes the following types visible:
- •
- i_img - used to represent an image
- •
- i_color - used to represent a color with up to 8 bits per
sample.
- •
- i_fcolor - used to represent a color with a double per
sample.
- •
- i_fill_t - an abstract fill
At this point there is no consolidated font object type, and hence the font
functions are not visible through Imager's API.
i_img - images¶
This contains the dimensions of the image ("xsize", "ysize",
"channels"), image metadata ("ch_mask", "bits",
"type", "virtual"), potentially image data
("idata") and the a function table, with pointers to functions to
perform various low level image operations.
The only time you should directly write to any value in this type is if you're
implementing your own image type.
The typemap includes type names Imager and Imager::ImgRaw as typedefs for
"i_img *".
For incoming parameters the typemap will accept either Imager or Imager::ImgRaw
objects.
For return values the typemap will produce a full Imager object for an Imager
return type and a raw image object for an Imager::ImgRaw return type.
"i_color" - 8-bit color¶
Represents an 8-bit per sample color. This is a union containing several
different structs for access to components of a color:
- •
- "gray" - single member
"gray_color".
- •
- "rgb" - "r", "g",
"b" members.
- •
- "rgba" - "r", "g",
"b", "a" members.
- •
- "channels" - array of channels.
Use Imager::Color for parameter and return value types.
"i_fcolor" - floating point color¶
Similar to "i_color" except that each component is a double instead of
an unsigned char.
Use Imager::Color::Float for parameter and return value types.
"i_fill_t" - fill objects¶
Abstract type containing pointers called to perform low level fill operations.
Unless you're defining your own fill objects you should treat this as an opaque
type.
Use Imager::FillHandle for parameter and return value types. At the Perl level
this is stored in the "fill" member of the Perl level Imager::Fill
object.
Create an XS module using the Imager API¶
Foo.pm¶
Load Imager:
use Imager 0.48;
and bootstrap your XS code - see XSLoader or DynaLoader.
"Foo.xs"¶
You'll need the following in your XS source:
- •
- include the Imager external API header, and the perl
interface header:
#include "imext.h"
#include "imperl.h"
- •
- create the variables used to hold the callback table:
DEFINE_IMAGER_CALLBACKS;
- •
- initialize the callback table in your "BOOT"
code:
BOOT:
PERL_INITIALIZE_IMAGER_CALLBACKS;
From Imager 0.91 you can supply your module name to improve error reporting:
BOOT:
PERL_INITIALIZE_IMAGER_CALLBACKS_NAME("My::Module");
foo.c¶
In any other source files where you want to access the Imager API, you'll need
to:
- •
- include the Imager external API header:
#include "imext.h"
"Makefile.PL"¶
If you're creating an XS module that depends on Imager's API your
"Makefile.PL" will need to do the following:
- •
- "use Imager::ExtUtils;"
- •
- include Imager's include directory in INC:
INC => Imager::ExtUtils->includes
- •
- use Imager's typemap:
TYPEMAPS => [ Imager::ExtUtils->typemap ]
- •
- include Imager 0.48 as a PREREQ_PM:
PREREQ_PM =>
{
Imager => 0.48,
},
- •
- Since you use Imager::ExtUtils in "Makefile.PL"
(or "Build.PL") you should include Imager in your
configure_requires:
META_MERGE =>
{
configure_requires => { Imager => "0.48" }
},
AUTHOR¶
Tony Cook <tonyc@cpan.org>
SEE ALSO¶
Imager, Imager::ExtUtils, Imager::APIRef, Imager::Inline