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/* See LICENSE file for copyright and license details. */
#include "common.h"
#ifndef TEST
void
rtgrpblib_draw_linear_bezier(RASTER *restrict raster, double x1, double y1, double x2, double y2)
{
double w, h, dx, dy, x, y;
int xdir, ydir;
dx = x2 - x1;
dy = y2 - y1;
xdir = SIGNUM(dx);
ydir = SIGNUM(dy);
if (!ydir) {
/* For horizontal lines, it is enough that we have the
* corners mapped onto the raster, which we must have
* since a glyph cannot just contain a line, but outlines:
* in `fill`, the line will not make a contribution because
* `.opposite_coverage` for each cell will be zero, and
* consequentially, `.cell_coverage` will also be zero */
return;
}
/* We cut of everything above and below the raster,
* as these do not contribute to the result */
h = (double)raster->height;
if (y1 < 0 && y2 < 0)
return;
if (y1 >= h && y2 >= h)
return;
if (y1 < 0 && y2 >= 0) {
x1 = x1 + (0 - y1) * dx / dy;
y1 = 0;
} else if (y2 < 0 && y1 >= 0) {
x2 = x1 + (0 - y1) * dx / dy;
y2 = 0;
}
if (y1 < h && y2 >= h) {
x2 = x1 + (h - y1) * dx / dy;
y2 = h;
} else if (y2 < h && y1 >= h) {
x1 = x1 + (h - y1) * dx / dy;
y1 = h;
}
/* Dealing with the left and the right section
* is not as simple as `fill` assumes that the
* sum of each line's `.opposite_coverage` is 0.
* Therefore must must identify the parts of the
* line that are left of the raster, right of
* the raster, and inside the raster. The parts
* that are outside the raster are move to the
* edge, or rather their show on the edges are
* used. */
w = (double)raster->width;
if (x1 <= 0 && x2 <= 0) {
draw_vertical_line(raster, 0, y1, y2, ydir);
return;
}
if (x1 >= w && x2 >= w) {
draw_vertical_line_opposite_only(raster, raster->width - 1, y1, y2, ydir);
return;
}
if (x1 < 0 && x2 >= 0) {
y = y1 + (0 - x1) * dy / dx;
x = 0;
draw_vertical_line(raster, 0, y1, y, ydir);
x1 = x;
y1 = y;
} else if (x2 < 0 && x1 >= 0) {
y = y1 + (0 - x1) * dy / dx;
x = 0;
draw_vertical_line(raster, 0, y, y2, ydir);
x2 = x;
y2 = y;
}
if (x1 < w && x2 >= w) {
y = y1 + (w - x1) * dy / dx;
x = w;
draw_vertical_line_opposite_only(raster, raster->width - 1, y, y2, ydir);
x2 = x;
y2 = y;
} else if (x2 < w && x1 >= w) {
y = y1 + (w - x1) * dy / dx;
x = w;
draw_vertical_line_opposite_only(raster, raster->width - 1, y1, y, ydir);
x1 = x;
y1 = y;
}
/* Now we can finally draw the part of the
* line that is inside the raster */
if (!xdir) {
/* Optimisation for vertical lines. It also serves
* to illustrate how the algorithm is designed. */
draw_vertical_line(raster, x1, y1, y2, ydir);
} else {
draw_diagonal_line(raster, x1, y1, x2, y2, dx, dy, xdir, ydir);
}
}
#else
int
main(void)
{
return 0; /* TODO add test */
}
#endif
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