libvips/libvips/resample/resample.c

/* base class for all resample operations
 *
 * properties:
 * 	- one in, one out
 * 	- not point-to-point
 * 	- size can change in any way
 * 	- bands, type, format etc. all fixed
 */

/*

    Copyright (C) 1991-2005 The National Gallery

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU 
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <vips/vips.h>
#include <vips/internal.h>

#include "presample.h"

/**
 * SECTION: resample
 * @short_description: resample images in various ways
 * @stability: Stable
 * @include: vips/vips.h
 *
 * These operations build on each other in a set of layers.
 *
 * First, vips_affine() applies an affine transform to an image. This is any
 * sort of 2D transform which preserves straight lines; so any combination of 
 * stretch, sheer, rotate and translate. You supply an interpolator for it to
 * use to generate pixels, see vips_interpolate_new(). It will not produce
 * good results for very large shrinks: you'll see aliasing.
 *
 * vips_reduce() is like vips_affine(), but it can only shrink images, it can't
 * enlarge, rotate, or skew. It's very fast and uses an adaptive kernel for
 * interpolation.
 *
 * vips_shrink() is a fast block shrinker. It can quickly reduce images by
 * large integer factors. It will give poor results for small size reductions:
 * again, you'll see aliasing. 
 *
 * Next, vips_resize() specialises in the common task of image reduce and 
 * enlarge. It strings together combinations of vips_shrink(), vips_reduce(),
 * vips_affine() and others to implement a general, high-quality image
 * resizer.
 *
 * Finally, vips_thumbnail() combines load and resize in one operation, and adds
 * colour management and correct handling of alpha transparency. Because load
 * and resize happen together, it can exploit tricks like JPEG and TIFF
 * shrink-on-load, giving a (potentially) huge speedup. vips_thumbnail_image() 
 * is only there for emergencies, don't use it unless you really have to.
 *
 * As a separate thing, `vips_mapim() can apply arbitrary 2D image transforms 
 * to an image.
 */

/** 
 * VipsSize:
 * @VIPS_SIZE_BOTH: size both up and down
 * @VIPS_SIZE_UP: only upsize
 * @VIPS_SIZE_DOWN: only downsize
 * @VIPS_SIZE_FORCE: force size, that is, break aspect ratio
 *
 * Controls whether an operation should upsize, downsize, both up and
 * downsize, or force a size.
 *
 * See also: vips_thumbnail().
 */

G_DEFINE_ABSTRACT_TYPE( VipsResample, vips_resample, VIPS_TYPE_OPERATION );

static int
vips_resample_build( VipsObject *object )
{
	VipsResample *resample = VIPS_RESAMPLE( object );

#ifdef DEBUG
	printf( "vips_resample_build: " );
	vips_object_print_name( object );
	printf( "\n" );
#endif /*DEBUG*/

	g_object_set( resample, "out", vips_image_new(), NULL ); 

	if( VIPS_OBJECT_CLASS( vips_resample_parent_class )->build( object ) )
		return( -1 );

	return( 0 );
}

static void
vips_resample_class_init( VipsResampleClass *class )
{
	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "resample";
	vobject_class->description = _( "resample operations" );
	vobject_class->build = vips_resample_build;

	VIPS_ARG_IMAGE( class, "in", 1, 
		_( "Input" ), 
		_( "Input image argument" ),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET( VipsResample, in ) );

	VIPS_ARG_IMAGE( class, "out", 2, 
		_( "Output" ), 
		_( "Output image" ),
		VIPS_ARGUMENT_REQUIRED_OUTPUT, 
		G_STRUCT_OFFSET( VipsResample, out ) );

}

static void
vips_resample_init( VipsResample *resample )
{
}

/* Called from iofuncs to init all operations in this dir. Use a plugin system
 * instead?
 */
void
vips_resample_operation_init( void )
{
	extern GType vips_thumbnail_file_get_type( void ); 
	extern GType vips_thumbnail_buffer_get_type( void ); 
	extern GType vips_thumbnail_image_get_type( void ); 
	extern GType vips_thumbnail_source_get_type( void ); 
	extern GType vips_mapim_get_type( void ); 
	extern GType vips_shrink_get_type( void ); 
	extern GType vips_shrinkh_get_type( void ); 
	extern GType vips_shrinkv_get_type( void ); 
	extern GType vips_reduce_get_type( void ); 
	extern GType vips_reduceh_get_type( void ); 
	extern GType vips_reducev_get_type( void ); 
	extern GType vips_quadratic_get_type( void ); 
	extern GType vips_affine_get_type( void ); 
	extern GType vips_similarity_get_type( void ); 
	extern GType vips_rotate_get_type( void ); 
	extern GType vips_resize_get_type( void ); 

	vips_thumbnail_file_get_type(); 
	vips_thumbnail_buffer_get_type(); 
	vips_thumbnail_image_get_type(); 
	vips_thumbnail_source_get_type(); 
	vips_mapim_get_type(); 
	vips_shrink_get_type(); 
	vips_shrinkh_get_type(); 
	vips_shrinkv_get_type(); 
	vips_reduceh_get_type(); 
	vips_reducev_get_type(); 
	vips_reduce_get_type(); 
	vips_quadratic_get_type(); 
	vips_affine_get_type(); 
	vips_similarity_get_type(); 
	vips_rotate_get_type(); 
	vips_resize_get_type(); 
}