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text: New path stroking algorithm

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This commit is contained in:
K. Lange 2023-03-27 17:13:05 +09:00
parent 527de1fe48
commit 0f56a62f3c
1 changed files with 104 additions and 12 deletions
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116
lib/text.c
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@ -1116,21 +1116,113 @@ char * tt_get_name_string(struct TT_Font * font, int identifier) {
return NULL;
}
struct PenPoly {
float x;
float y;
float inner;
float outer;
float basis;
};
static float tangent(float x_0, float y_0, float x_1, float y_1) {
return fmod(atan2(y_0 - y_1, x_1 - x_0) + 2.0 * M_PI, 2.0 * M_PI);
}
static int angle_compare(float s, struct PenPoly * pen, int a) {
if (s >= pen[a].inner && s < pen[a].outer) return 0;
if (s >= pen[a].inner && pen[a].outer < pen[a].inner) return 0;
if (s < pen[a].outer && pen[a].outer < pen[a].inner) return 0;
if (s < pen[a].outer && (2.0 * M_PI + s - pen[a].outer > M_PI)) return 1;
if (s > pen[a].outer && (s - pen[a].outer > M_PI)) return 1;
return -1;
}
static int best_angle(int sides, struct PenPoly * pen, float s) {
for (int a = 0; a < sides; ++a) {
if (angle_compare(s,pen,a) == 0) return a;
}
return 0;
}
struct TT_Shape * tt_contour_stroke_shape(struct TT_Contour * in, float width) {
struct TT_Contour * stroke = tt_contour_start(0,0);
for (size_t i = 0; i < in->edgeCount; ++i) {
double x_vect = in->edges[i].end.x - in->edges[i].start.x;
double y_vect = in->edges[i].end.y - in->edges[i].start.y;
double len = sqrt(x_vect * x_vect + y_vect * y_vect);
if (len == 0.0) continue;
double x_norm = (-y_vect / len) * width;
double y_norm = (x_vect / len) * width;
stroke = tt_contour_move_to(stroke, x_norm + in->edges[i].start.x, y_norm + in->edges[i].start.y);
stroke = tt_contour_line_to(stroke, x_norm + in->edges[i].end.x, y_norm + in->edges[i].end.y);
stroke = tt_contour_line_to(stroke, -x_norm + in->edges[i].end.x, -y_norm + in->edges[i].end.y);
stroke = tt_contour_line_to(stroke, -x_norm + in->edges[i].start.x, -y_norm + in->edges[i].start.y);
stroke = tt_contour_line_to(stroke, x_norm + in->edges[i].start.x, y_norm + in->edges[i].start.y);
if (in->edgeCount) {
int sides = width < 1.0 ? 4 : 16;
float inner = 2.0 * M_PI / (float)sides;
float outer = (M_PI - inner) / 2.0;
struct PenPoly * pen = malloc(sizeof(struct PenPoly) * sides); /* Arbitrary */
for (int i = 0; i < sides; ++i) {
float angle = (float)i * 2.0 * M_PI / (float)sides;
pen[i].x = cos(angle) * width;
pen[i].y = -sin(angle) * width;
pen[i].basis = angle;
pen[i].inner = fmod(angle + outer, 2.0 * M_PI);
pen[i].outer = fmod(angle + outer + inner, 2.0 * M_PI);
}
int start_of_segment = 0;
int next_segment = (int)in->edgeCount;
do {
int started = 0;
int v = start_of_segment;
float s = tangent(in->edges[v].start.x, in->edges[v].start.y, in->edges[v].end.x, in->edges[v].end.y);
int a = best_angle(sides,pen,s);
while (v < (int)in->edgeCount) {
s = tangent(in->edges[v].start.x, in->edges[v].start.y, in->edges[v].end.x, in->edges[v].end.y);
stroke = (started ? tt_contour_line_to : tt_contour_move_to)(stroke, pen[a].x + in->edges[v].start.x, pen[a].y + in->edges[v].start.y);
started = 1;
int comp = angle_compare(s,pen,a);
if (comp == 0) {
if (v + 1 == (int)in->edgeCount) {
next_segment = in->edgeCount;
break;
}
if (in->edges[v+1].start.x != in->edges[v].end.x || in->edges[v+1].start.y != in->edges[v].end.y) {
next_segment = v + 1;
break;
}
v++;
} else if (comp == 1) {
a = (sides + a - 1) % sides;
} else {
a = (a + 1) % sides;
}
}
while (v >= start_of_segment) {
s = tangent(in->edges[v].end.x, in->edges[v].end.y, in->edges[v].start.x, in->edges[v].start.y);
stroke = tt_contour_line_to(stroke, in->edges[v].end.x + pen[a].x, in->edges[v].end.y + pen[a].y);
int comp = angle_compare(s,pen,a);
if (comp == 0) {
if (v == start_of_segment) break;
v--;
} else if (comp == 1) {
a = (sides + a - 1) % sides;
} else {
a = (a + 1) % sides;
}
}
while (v == start_of_segment) {
s = tangent(in->edges[v].start.x, in->edges[v].start.y, in->edges[v].end.x, in->edges[v].end.y);
stroke = tt_contour_line_to(stroke, pen[a].x + in->edges[v].start.x, pen[a].y + in->edges[v].start.y);
int comp = angle_compare(s,pen,a);
if (comp == 0) {
break;
} else if (comp == 1) {
a = (sides + a - 1) % sides;
} else {
a = (a + 1) % sides;
}
}
start_of_segment = next_segment;
} while (next_segment != (int)in->edgeCount);
free(pen);
}
struct TT_Shape * out = tt_contour_finish(stroke);