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// SPDX-License-Identifier: GPL-2.0-or-later
/** @file
* TODO: insert short description here
*//*
* Authors:
* see git history
* Fred
*
* Copyright (C) 2018 Authors
* Released under GNU GPL v2+, read the file 'COPYING' for more information.
*/
#ifndef my_alpha_ligne
#define my_alpha_ligne
#include "LivarotDefs.h"
/*
* pixel coverage of a line, libart style: each pixel coverage is obtained from the coverage of the previous one by
* adding a delta given by a step. the goal is to have only a limited number of positions where the delta != 0, so that
* you only have to store a limited number of steps.
*/
// a step
struct alpha_step {
int x; // position
float delta; // increase or decrease in pixel coverage with respect to the coverage of the previous pixel
};
class AlphaLigne {
public:
// bounds of the line
// necessary since the visible portion of the canvas is bounded, and you need to compute
// the value of the pixel "just before the visible portion of the line"
int min,max;
int length;
// before is the step containing the delta relative to a pixel infinitely far on the left of the line
// thus the initial pixel coverage is before.delta
alpha_step before,after;
// array of steps
int nbStep,maxStep;
alpha_step* steps;
// bounds of the portion of the line that has received some coverage
int curMin,curMax;
// iMin and iMax are the bounds of the visible portion of the line
AlphaLigne(int iMin,int iMax);
virtual ~AlphaLigne();
// empties the line
void Reset();
// add some coverage.
// pente is (eval-sval)/(epos-spos), because you can compute it once per edge, and thus spare the
// CPU some potentially costly divisions
int AddBord(float spos,float sval,float epos,float eval,float iPente);
// version where you don't have the pente parameter
int AddBord(float spos,float sval,float epos,float eval);
// sorts the steps in increasing order. needed before you raster the line
void Flatten();
// debug dump of the steps
void Affiche();
// private
void AddRun(int st,float pente);
// raster the line in the buffer given in "dest", with the rasterization primitive worker
// worker() is given the color parameter each time it is called. the type of the function is
// defined in LivarotDefs.h
void Raster(raster_info &dest,void* color,RasterInRunFunc worker);
// also private. that's the comparison function given to qsort()
static int CmpStep(const void * p1, const void * p2) {
alpha_step* d1=(alpha_step*)p1;
alpha_step* d2=(alpha_step*)p2;
return d1->x - d2->x ;
};
};
#endif
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