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Reimplement line algorithm (fix #1395)

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This commit is contained in:
David Capello 2017-06-22 21:10:44 -03:00
parent ac44c4ab97
commit 88e0596692
1 changed files with 40 additions and 80 deletions
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120
src/doc/algo.cpp
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@ -1,5 +1,5 @@
// Aseprite Document Library
// Copyright (c) 2001-2016 David Capello
// Copyright (c) 2001-2017 David Capello
//
// This file is released under the terms of the MIT license.
// Read LICENSE.txt for more information.
@ -8,94 +8,54 @@
#include "config.h"
#endif
#include <math.h>
#include "base/base.h"
#include "doc/algo.h"
#include <algorithm>
#include <cmath>
namespace doc {
// Algorightm from Allegro (allegro/src/gfx.c)
// Adapted for Aseprite by David Capello.
void algo_line(int x1, int y1, int x2, int y2, void *data, AlgoPixel proc)
void algo_line(int x1, int y1, int x2, int y2, void* data, AlgoPixel proc)
{
int dx = x2-x1;
int dy = y2-y1;
int i1, i2;
int x, y;
int dd;
bool yaxis;
/* worker macro */
#define DO_LINE(pri_sign, pri_c, pri_cond, sec_sign, sec_c, sec_cond) \
{ \
if (d##pri_c == 0) { \
proc(x1, y1, data); \
return; \
} \
\
i1 = 2 * d##sec_c; \
dd = i1 - (sec_sign (pri_sign d##pri_c)); \
i2 = dd - (sec_sign (pri_sign d##pri_c)); \
\
x = x1; \
y = y1; \
\
while (pri_c pri_cond pri_c##2) { \
proc(x, y, data); \
\
if (dd sec_cond 0) { \
sec_c sec_sign##= 1; \
dd += i2; \
} \
else \
dd += i1; \
\
pri_c pri_sign##= 1; \
} \
// If the height if the line is bigger than the width, we'll iterate
// over the y-axis.
if (ABS(y2-y1) > ABS(x2-x1)) {
std::swap(x1, y1);
std::swap(x2, y2);
yaxis = true;
}
else
yaxis = false;
if (dx >= 0) {
if (dy >= 0) {
if (dx >= dy) {
/* (x1 <= x2) && (y1 <= y2) && (dx >= dy) */
DO_LINE(+, x, <=, +, y, >=);
}
else {
/* (x1 <= x2) && (y1 <= y2) && (dx < dy) */
DO_LINE(+, y, <=, +, x, >=);
}
}
else {
if (dx >= -dy) {
/* (x1 <= x2) && (y1 > y2) && (dx >= dy) */
DO_LINE(+, x, <=, -, y, <=);
}
else {
/* (x1 <= x2) && (y1 > y2) && (dx < dy) */
DO_LINE(-, y, >=, +, x, >=);
}
}
}
else {
if (dy >= 0) {
if (-dx >= dy) {
/* (x1 > x2) && (y1 <= y2) && (dx >= dy) */
DO_LINE(-, x, >=, +, y, >=);
}
else {
/* (x1 > x2) && (y1 <= y2) && (dx < dy) */
DO_LINE(+, y, <=, -, x, <=);
}
}
else {
if (-dx >= -dy) {
/* (x1 > x2) && (y1 > y2) && (dx >= dy) */
DO_LINE(-, x, >=, -, y, <=);
}
else {
/* (x1 > x2) && (y1 > y2) && (dx < dy) */
DO_LINE(-, y, >=, -, x, <=);
}
const int w = ABS(x2-x1)+1;
const int h = ABS(y2-y1)+1;
const int dx = SGN(x2-x1);
const int dy = SGN(y2-y1);
int e = 0;
int y = y1;
// Move one x2 extra pixels to the dx direction so we can use
// operator!=() instead of operator<(). Here I prefer operator!=()
// instead of swapping x1 with x2 so the error always start from 0
// in the origin (x1,y1).
x2 += dx;
for (int x=x1; x!=x2; x+=dx) {
if (yaxis)
proc(y, x, data);
else
proc(x, y, data);
// The error advances "h/w" per each "x" step. As we're using a
// integer value for "e", we use "w" as the unit.
e += h;
if (e >= w) {
y += dy;
e -= w;
}
}
}