101 lines
3.9 KiB
C
101 lines
3.9 KiB
C
/*
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* Copyright 2009 Stefan Gustavson (stefan.gustavson@gmail.com)
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY STEFAN GUSTAVSON ''AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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* EVENT SHALL STEFAN GUSTAVSON OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* The views and conclusions contained in the software and documentation are
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* those of the authors and should not be interpreted as representing official
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* policies, either expressed or implied, of Stefan Gustavson.
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*
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*
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* edtaa3()
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*
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* Sweep-and-update Euclidean distance transform of an
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* image. Positive pixels are treated as object pixels,
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* zero or negative pixels are treated as background.
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* An attempt is made to treat antialiased edges correctly.
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* The input image must have pixels in the range [0,1],
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* and the antialiased image should be a box-filter
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* sampling of the ideal, crisp edge.
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* If the antialias region is more than 1 pixel wide,
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* the result from this transform will be inaccurate.
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*
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* By Stefan Gustavson (stefan.gustavson@gmail.com).
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*
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* Originally written in 1994, based on a verbal
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* description of the SSED8 algorithm published in the
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* PhD dissertation of Ingemar Ragnemalm. This is his
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* algorithm, I only implemented it in C.
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*
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* Updated in 2004 to treat border pixels correctly,
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* and cleaned up the code to improve readability.
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*
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* Updated in 2009 to handle anti-aliased edges.
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*
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* Updated in 2011 to avoid a corner case infinite loop.
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*
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*/
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#ifndef __EDTAA3FUNC_H__
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#define __EDTAA3FUNC_H__
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <math.h>
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/*
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* Compute the local gradient at edge pixels using convolution filters.
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* The gradient is computed only at edge pixels. At other places in the
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* image, it is never used, and it's mostly zero anyway.
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*/
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void computegradient(double *img, int w, int h, double *gx, double *gy);
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/*
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* A somewhat tricky function to approximate the distance to an edge in a
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* certain pixel, with consideration to either the local gradient (gx,gy)
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* or the direction to the pixel (dx,dy) and the pixel greyscale value a.
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* The latter alternative, using (dx,dy), is the metric used by edtaa2().
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* Using a local estimate of the edge gradient (gx,gy) yields much better
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* accuracy at and near edges, and reduces the error even at distant pixels
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* provided that the gradient direction is accurately estimated.
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*/
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double edgedf(double gx, double gy, double a);
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double distaa3(double *img, double *gximg, double *gyimg, int w, int c, int xc, int yc, int xi, int yi);
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// Shorthand macro: add ubiquitous parameters dist, gx, gy, img and w and call distaa3()
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#define DISTAA(c,xc,yc,xi,yi) (distaa3(img, gx, gy, w, c, xc, yc, xi, yi))
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void edtaa3(double *img, double *gx, double *gy, int w, int h, short *distx, short *disty, double *dist);
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#ifdef __cplusplus
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}
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#endif
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#endif // __EDTAA3FUNC_H__
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