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
|
/* See LICENSE file for copyright and license details. */
#include "common.h"
#ifndef TEST
/*
* The implementation in this fill is not supposed to be fast,
* it is supposed to be absolutely correct. The implementation
* shall be as clear and obvious as possible. It is important
* that everything written to cells is as precise as possible
* and that the function behavious correctly when outside the
* raster. This implementation shall be usable to generate an
* as perfect as possible rasterisation and shall be usable to
* test the correctness and accuracy of the fast implementation.
*/
void
draw_linear_bezier_reference(RASTER *restrict raster, double x1, double y1, double x2, double y2)
{
double dx = x2 - x1;
double dy = y2 - y1;
int xdir = SIGNUM(dx);
int ydir = SIGNUM(dy);
double kx = dx / dy;
double ky = dy / dx;
double prevX, prevY, x, y, cx, cy, h2x, h2y;
double xfloor, yfloor;
ssize_t cellX, cellY;
size_t cell;
prevX = x1;
prevY = y1;
for (; prevX != x2 && prevY != y2; prevX = x, prevY = y) {
/* Find next vertical and next hozitonal grid line */
x = xdir < 0 ? floor(prevX) : xdir > 0 ? ceil(prevX) : prevX;
y = ydir < 0 ? floor(prevY) : ydir > 0 ? ceil(prevY) : prevY;
x = x == prevX ? x + xdir : x;
y = y == prevY ? y + ydir : y;
/* Limit to the extend of the drawn line segment */
if ((xdir < 0 && x < x2) || (xdir > 0 && x > x2))
x = x2;
if ((ydir < 0 && y < y2) || (ydir > 0 && y > y2))
y = y2;
/* Find next cell edge */
if (xdir && ydir) {
cy = y1 + (x - x1) * ky;
cx = x1 + (y - y1) * kx;
h2x = (cy - prevY) * (cy - prevY) + (x - prevX) * (x - prevX);
h2y = (cx - prevX) * (cx - prevX) + (y - prevY) * (y - prevY);
if (h2x < h2y)
y = cy;
else
x = cx;
/* Make sure loop will exit when we reach the end */
if ((xdir < 0 && x < x2) || (xdir > 0 && x > x2))
x = x2;
if ((ydir < 0 && y < y2) || (ydir > 0 && y > y2))
y = y2;
}
/* Select cell to draw in */
xfloor = xdir >= 0 ? floor(prevX) : floor(x);
yfloor = ydir >= 0 ? floor(prevY) : floor(y);
cellX = (ssize_t)xfloor;
cellY = (ssize_t)yfloor;
/* Do not draw if above or below the raster*/
if (cellY < 0 || (size_t)cellY >= raster->height)
continue;
if (cellX < 0) {
/* Draw on first column in raster of outside of raster on the left side,
* with full horizontal coverage, `.opposite_coverage` one the actual
* cell (outside of the raster) will contribute to the first column's
* `.cell_coverage` */
cell = (size_t)cellY * raster->width;
raster->cells[cell].opposite_coverage += y - prevY;
raster->cells[cell].cell_coverage += y - prevY;
} else if ((size_t)cellX >= raster->width) {
/* If outside of the raster, on the right side, add to the last
* columns contributions to the next column, so that the ink level
* balances out to zero */
cell = (size_t)cellY * raster->width + (raster->width - 1);
raster->cells[cell].opposite_coverage += y - prevY;
} else {
/* If inside the raster, just draw the line */
cell = (size_t)cellY * raster->width + (size_t)cellX;
raster->cells[cell].opposite_coverage += y - prevY;
raster->cells[cell].cell_coverage += (y - prevY) * fabs(fmax(ceil(x), ceil(prevX)) - (x + prevX) / 2.0);
}
}
}
#else
int
main(void)
{
return 0; /* TODO add test */
}
#endif
|
