mirror of https://github.com/axmolengine/axmol.git
102 lines
3.7 KiB
C
102 lines
3.7 KiB
C
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/*
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Copyright (C) 2009 Stefan Gustavson (stefan.gustavson@gmail.com)
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This software is distributed under the permissive "MIT License":
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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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 Per-Erik Danielsson's SSED8 algorithm
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* as presented in the PhD dissertation of Ingemar
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* Ragnemalm. This is Per-Erik Danielsson's scanline
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* scheme from 1979 - 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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* as published in the article "Anti-aliased Euclidean
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* distance transform" by Stefan Gustavson and Robin Strand,
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* Pattern Recognition Letters 32 (2011) 252<EFBFBD>C257.
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*
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* Updated in 2011 to avoid a corner case causing an
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* infinite loop for some input data.
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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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