119 lines
4.3 KiB
C
119 lines
4.3 KiB
C
/* Yafrsmooth (catmull-rom) interpolator.
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifndef VIPS_YAFRSMOOTH_H
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#define VIPS_YAFRSMOOTH_H
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#ifdef __cplusplus
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extern "C" {
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#endif /*__cplusplus*/
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#define VIPS_TYPE_INTERPOLATE_YAFRSMOOTH \
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(vips_interpolate_yafrsmooth_get_type())
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#define VIPS_INTERPOLATE_YAFRSMOOTH( obj ) \
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(G_TYPE_CHECK_INSTANCE_CAST( (obj), \
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VIPS_TYPE_INTERPOLATE_YAFRSMOOTH, VipsInterpolateYafrsmooth ))
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#define VIPS_INTERPOLATE_YAFRSMOOTH_CLASS( klass ) \
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(G_TYPE_CHECK_CLASS_CAST( (klass), \
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VIPS_TYPE_INTERPOLATE_YAFRSMOOTH, VipsInterpolateYafrsmoothClass))
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#define VIPS_IS_INTERPOLATE_YAFRSMOOTH( obj ) \
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(G_TYPE_CHECK_INSTANCE_TYPE( (obj), VIPS_TYPE_INTERPOLATE_YAFRSMOOTH ))
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#define VIPS_IS_INTERPOLATE_YAFRSMOOTH_CLASS( klass ) \
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(G_TYPE_CHECK_CLASS_TYPE( (klass), VIPS_TYPE_INTERPOLATE_YAFRSMOOTH ))
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#define VIPS_INTERPOLATE_YAFRSMOOTH_GET_CLASS( obj ) \
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(G_TYPE_INSTANCE_GET_CLASS( (obj), \
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VIPS_TYPE_INTERPOLATE_YAFRSMOOTH, VipsInterpolateYafrsmoothClass ))
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typedef struct _VipsInterpolateYafrsmooth {
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VipsInterpolate parent_object;
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/* "sharpening" is a continuous method parameter which is
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* proportional to the amount of "diagonal straightening" which the
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* nonlinear correction part of the method may add to the underlying
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* linear scheme. You may also think of it as a sharpening
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* parameter: higher values correspond to more sharpening, and
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* negative values lead to strange looking effects.
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*
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* The default value is sharpening = 29/32 when the scheme being
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* "straightened" is Catmull-Rom---as is the case here. This value
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* fixes key pixel values near the diagonal boundary between two
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* monochrome regions (the diagonal boundary pixel values being set
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* to the halfway colour).
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*
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* If resampling seems to add unwanted texture artifacts, push
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* sharpening toward 0. It is not generally not recommended to set
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* sharpening to a value larger than 4.
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*
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* Sharpening is halved because the .5 which has to do with the
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* relative coordinates of the evaluation points (which has to do
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* with .5*rite_width etc) is folded into the constant to save
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* flops. Consequently, the largest recommended value of
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* sharpening_over_two is 2=4/2.
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*
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* In order to simplify interfacing with users, the parameter which
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* should be set by the user is normalized so that user_sharpening =
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* 1 when sharpening is equal to the recommended value. Consistently
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* with the above discussion, values of user_sharpening between 0
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* and about 3.625 give good results.
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*/
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double sharpening;
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} VipsInterpolateYafrsmooth;
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typedef struct _VipsInterpolateYafrsmoothClass {
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VipsInterpolateClass parent_class;
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/* Precalculated interpolation matricies. int (used for pel sizes up
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* to short), and double (for all others). We go to scale + 1, so
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* we can round-to-nearest safely.
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*/
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/* We could keep a large set of 2d 4x4 matricies, but this actually
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* works out slower, since for many resizes the thing will no longer
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* fit in L1.
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*/
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int matrixi[VIPS_TRANSFORM_SCALE + 1][4];
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double matrixf[VIPS_TRANSFORM_SCALE + 1][4];
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} VipsInterpolateYafrsmoothClass;
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GType vips_interpolate_yafrsmooth_get_type( void );
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VipsInterpolate *vips_interpolate_yafrsmooth_new( void );
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void vips_interpolate_yafrsmooth_set_sharpening( VipsInterpolateYafrsmooth *,
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double sharpening );
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/* Convenience: return a static default yafrsmooth, so no need to free it.
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*/
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VipsInterpolate *vips_interpolate_yafrsmooth_static( void );
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#ifdef __cplusplus
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}
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#endif /*__cplusplus*/
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#endif /*VIPS_YAFRSMOOTH_H*/
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