Class
VipsForeignLoad
Description [src]
abstract class Vips.ForeignLoad : Vips.Foreign
{
VipsImage* out,
VipsImage* real,
gboolean nocache,
gboolean disc,
gboolean error,
gboolean revalidate
}An abstract base class to load images in a variety of formats.
Writing a new loader
Add a new loader to libvips by subclassing VipsForeignLoad. Subclasses
need to implement at least Vips.ForeignLoadClass.header.
Vips.ForeignLoadClass.header must set at least the header fields of out.
Vips.ForeignLoadClass.load, if defined, must load the pixels to real.
The suffix list is used to select a format to save a file in, and to pick a
loader if you don’t define vips_foreign_is_a().
You should also define VipsObject:nickname and
VipsObject:description in VipsObject.
As a complete example, here’s code for a PNG loader, minus the actual calls to libpng.
typedef struct _VipsForeignLoadPng {
VipsForeignLoad parent_object;
char *filename;
} VipsForeignLoadPng;
typedef VipsForeignLoadClass VipsForeignLoadPngClass;
G_DEFINE_TYPE(VipsForeignLoadPng, vips_foreign_load_png,
VIPS_TYPE_FOREIGN_LOAD);
static VipsForeignFlags
vips_foreign_load_png_get_flags_filename(const char *filename)
{
VipsForeignFlags flags;
flags = 0;
if (vips__png_isinterlaced(filename))
flags = VIPS_FOREIGN_PARTIAL;
else
flags = VIPS_FOREIGN_SEQUENTIAL;
return flags;
}
static VipsForeignFlags
vips_foreign_load_png_get_flags(VipsForeignLoad *load)
{
VipsForeignLoadPng *png = (VipsForeignLoadPng *) load;
return vips_foreign_load_png_get_flags_filename(png->filename);
}
static int
vips_foreign_load_png_header(VipsForeignLoad *load)
{
VipsForeignLoadPng *png = (VipsForeignLoadPng *) load;
if (vips__png_header(png->filename, load->out))
return -1;
return 0;
}
static int
vips_foreign_load_png_load(VipsForeignLoad *load)
{
VipsForeignLoadPng *png = (VipsForeignLoadPng *) load;
if (vips__png_read(png->filename, load->real))
return -1;
return 0;
}
static void
vips_foreign_load_png_class_init(VipsForeignLoadPngClass *class)
{
GObjectClass *gobject_class = G_OBJECT_CLASS(class);
VipsObjectClass *object_class = (VipsObjectClass *) class;
VipsForeignClass *foreign_class = (VipsForeignClass *) class;
VipsForeignLoadClass *load_class = (VipsForeignLoadClass *) class;
gobject_class->set_property = vips_object_set_property;
gobject_class->get_property = vips_object_get_property;
object_class->nickname = "pngload";
object_class->description = _("load png from file");
foreign_class->suffs = vips__png_suffs;
load_class->is_a = vips__png_ispng;
load_class->get_flags_filename =
vips_foreign_load_png_get_flags_filename;
load_class->get_flags = vips_foreign_load_png_get_flags;
load_class->header = vips_foreign_load_png_header;
load_class->load = vips_foreign_load_png_load;
VIPS_ARG_STRING(class, "filename", 1,
_("Filename"),
_("Filename to load from"),
VIPS_ARGUMENT_REQUIRED_INPUT,
G_STRUCT_OFFSET(VipsForeignLoadPng, filename),
NULL);
}
static void
vips_foreign_load_png_init(VipsForeignLoadPng *png)
{
}
Instance methods
Methods inherited from VipsOperation (3)
vips_operation_call_valist
vips_operation_get_flags
Returns the set of flags for this operation.
vips_operation_invalidate
Methods inherited from VipsObject (27)
Please see VipsObject for a full list of methods.
Signals
Signals inherited from VipsOperation (1)
Signals inherited from VipsObject (4)
VipsObject::close
The ::close signal is emitted once during object close. The object is dying and may not work.
VipsObject::postbuild
The ::postbuild signal is emitted once just after successful object construction. Return non-zero to cause object construction to fail.
VipsObject::postclose
The ::postclose signal is emitted once after object close. The object pointer is still valid, but nothing else.
VipsObject::preclose
The ::preclose signal is emitted once just before object close starts. The object is still alive.
Signals inherited from GObject (1)
GObject::notify
The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.
Class structure
struct VipsForeignLoadClass {
VipsForeignClass parent_class;
gboolean (* is_a) (
const char* filename
);
gboolean (* is_a_buffer) (
void* data,
size_t size
);
gboolean (* is_a_source) (
VipsSource* source
);
VipsForeignFlags (* get_flags_filename) (
const char* filename
);
VipsForeignFlags (* get_flags) (
VipsForeignLoad* load
);
int (* header) (
VipsForeignLoad* load
);
int (* load) (
VipsForeignLoad* load
);
}No description available.
Class members
parent_class: VipsForeignClassNo description available.
is_a: gboolean (* is_a) ( const char* filename )No description available.
is_a_buffer: gboolean (* is_a_buffer) ( void* data, size_t size )No description available.
is_a_source: gboolean (* is_a_source) ( VipsSource* source )No description available.
get_flags_filename: VipsForeignFlags (* get_flags_filename) ( const char* filename )No description available.
get_flags: VipsForeignFlags (* get_flags) ( VipsForeignLoad* load )No description available.
header: int (* header) ( VipsForeignLoad* load )No description available.
load: int (* load) ( VipsForeignLoad* load )No description available.