1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
/* $XConsortium: miscanfill.h,v 1.5 94/04/17 20:27:50 dpw Exp $ */
/*
Copyright (c) 1987 X Consortium
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of the X Consortium shall
not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization
from the X Consortium.
*/
#ifndef SCANFILLINCLUDED
#define SCANFILLINCLUDED
/*
* scanfill.h
*
* Written by Brian Kelleher; Jan 1985
*
* This file contains a few macros to help track
* the edge of a filled object. The object is assumed
* to be filled in scanline order, and thus the
* algorithm used is an extension of Bresenham's line
* drawing algorithm which assumes that y is always the
* major axis.
* Since these pieces of code are the same for any filled shape,
* it is more convenient to gather the library in one
* place, but since these pieces of code are also in
* the inner loops of output primitives, procedure call
* overhead is out of the question.
* See the author for a derivation if needed.
*/
/*
* In scan converting polygons, we want to choose those pixels
* which are inside the polygon. Thus, we add .5 to the starting
* x coordinate for both left and right edges. Now we choose the
* first pixel which is inside the pgon for the left edge and the
* first pixel which is outside the pgon for the right edge.
* Draw the left pixel, but not the right.
*
* How to add .5 to the starting x coordinate:
* If the edge is moving to the right, then subtract dy from the
* error term from the general form of the algorithm.
* If the edge is moving to the left, then add dy to the error term.
*
* The reason for the difference between edges moving to the left
* and edges moving to the right is simple: If an edge is moving
* to the right, then we want the algorithm to flip immediately.
* If it is moving to the left, then we don't want it to flip until
* we traverse an entire pixel.
*/
#define BRESINITPGON(dy, x1, x2, xStart, d, m, m1, incr1, incr2) { \
int dx; /* local storage */ \
\
/* \
* if the edge is horizontal, then it is ignored \
* and assumed not to be processed. Otherwise, do this stuff. \
*/ \
if ((dy) != 0) { \
xStart = (x1); \
dx = (x2) - xStart; \
if (dx < 0) { \
m = dx / (dy); \
m1 = m - 1; \
incr1 = -2 * dx + 2 * (dy) * m1; \
incr2 = -2 * dx + 2 * (dy) * m; \
d = 2 * m * (dy) - 2 * dx - 2 * (dy); \
} else { \
m = dx / (dy); \
m1 = m + 1; \
incr1 = 2 * dx - 2 * (dy) * m1; \
incr2 = 2 * dx - 2 * (dy) * m; \
d = -2 * m * (dy) + 2 * dx; \
} \
} \
}
#define BRESINCRPGON(d, minval, m, m1, incr1, incr2) { \
if (m1 > 0) { \
if (d > 0) { \
minval += m1; \
d += incr1; \
} \
else { \
minval += m; \
d += incr2; \
} \
} else {\
if (d >= 0) { \
minval += m1; \
d += incr1; \
} \
else { \
minval += m; \
d += incr2; \
} \
} \
}
/*
* This structure contains all of the information needed
* to run the bresenham algorithm.
* The variables may be hardcoded into the declarations
* instead of using this structure to make use of
* register declarations.
*/
typedef struct {
int minor; /* minor axis */
int d; /* decision variable */
int m, m1; /* slope and slope+1 */
int incr1, incr2; /* error increments */
} BRESINFO;
#define BRESINITPGONSTRUCT(dmaj, min1, min2, bres) \
BRESINITPGON(dmaj, min1, min2, bres.minor, bres.d, \
bres.m, bres.m1, bres.incr1, bres.incr2)
#define BRESINCRPGONSTRUCT(bres) \
BRESINCRPGON(bres.d, bres.minor, bres.m, bres.m1, bres.incr1, bres.incr2)
#endif
|
