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curve: Add gsk_curve_decompose_curve

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This is mainly useful for decomposing a conic into
cubics. The criterion here for terminating the
subdivision is very improvised.
This commit is contained in:
Matthias Clasen
2020-12-09 17:46:31 -05:00
parent 72835f321f
commit a9c36f8ba9
2 changed files with 135 additions and 0 deletions
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128
gsk/gskcurve.c
View File

@@ -52,6 +52,10 @@ struct _GskCurveClass
float tolerance,
GskCurveAddLineFunc add_line_func,
gpointer user_data);
gboolean (* decompose_curve) (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data);
gskpathop (* pathop) (const GskCurve *curve);
const graphene_point_t * (* get_start_point) (const GskCurve *curve);
const graphene_point_t * (* get_end_point) (const GskCurve *curve);
@@ -174,6 +178,23 @@ gsk_line_curve_decompose (const GskCurve *curve,
return add_line_func (&self->points[0], &self->points[1], 0.0f, 1.0f, user_data);
}
static gboolean
gsk_line_curve_decompose_curve (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data)
{
const GskLineCurve *self = &curve->line;
graphene_point_t p[4];
p[0] = self->points[0];
p[3] = self->points[1];
graphene_point_interpolate (&p[0], &p[3], 1/3.0, &p[1]);
graphene_point_interpolate (&p[0], &p[3], 2/3.0, &p[2]);
return add_curve_func (p, user_data);
}
static gskpathop
gsk_line_curve_pathop (const GskCurve *curve)
{
@@ -225,6 +246,7 @@ static const GskCurveClass GSK_LINE_CURVE_CLASS = {
gsk_line_curve_split,
gsk_line_curve_segment,
gsk_line_curve_decompose,
gsk_line_curve_decompose_curve,
gsk_line_curve_pathop,
gsk_line_curve_get_start_point,
gsk_line_curve_get_end_point,
@@ -406,6 +428,17 @@ gsk_curve_curve_decompose (const GskCurve *curve,
return gsk_curce_curve_decompose_step (curve, 0.0, 1.0, tolerance, add_line_func, user_data);
}
static gboolean
gsk_curve_curve_decompose_curve (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data)
{
const GskCurveCurve *self = &curve->curve;
return add_curve_func (self->points, user_data);
}
static gskpathop
gsk_curve_curve_pathop (const GskCurve *curve)
{
@@ -541,6 +574,7 @@ static const GskCurveClass GSK_CURVE_CURVE_CLASS = {
gsk_curve_curve_split,
gsk_curve_curve_segment,
gsk_curve_curve_decompose,
gsk_curve_curve_decompose_curve,
gsk_curve_curve_pathop,
gsk_curve_curve_get_start_point,
gsk_curve_curve_get_end_point,
@@ -909,6 +943,90 @@ gsk_conic_curve_decompose (const GskCurve *curve,
user_data);
}
/* See Floater, M: An analysis of cubic approximation schemes
* for conic sections
*/
static void
cubic_approximation (const GskCurve *curve,
GskCurve *cubic)
{
const GskConicCurve *self = &curve->conic;
graphene_point_t p[4];
float w = self->points[2].x;
float w2 = w*w;
float lambda;
lambda = 2 * (6*w2 + 1 - sqrt (3*w2 + 1)) / (12*w2 + 3);
p[0] = self->points[0];
p[3] = self->points[3];
graphene_point_interpolate (&self->points[0], &self->points[1], lambda, &p[1]);
graphene_point_interpolate (&self->points[3], &self->points[1], lambda, &p[2]);
gsk_curve_init (cubic, gsk_pathop_encode (GSK_PATH_CURVE, p));
}
static gboolean
gsk_conic_is_close_to_cubic (const GskCurve *conic,
const GskCurve *cubic,
float tolerance)
{
float t[] = { 0.1, 0.5, 0.9 };
graphene_point_t p0, p1;
for (int i = 0; i < G_N_ELEMENTS (t); i++)
{
gsk_curve_get_point (conic, t[i], &p0);
gsk_curve_get_point (cubic, t[i], &p1);
if (graphene_point_distance (&p0, &p1, NULL, NULL) > tolerance)
return FALSE;
}
return TRUE;
}
static gboolean gsk_conic_curve_decompose_curve (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data);
static gboolean
gsk_conic_curve_decompose_or_add (const GskCurve *curve,
const GskCurve *cubic,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data)
{
if (gsk_conic_is_close_to_cubic (curve, cubic, tolerance))
return add_curve_func (cubic->curve.points, user_data);
else
{
GskCurve c1, c2;
GskCurve cc1, cc2;
gsk_conic_curve_split (curve, 0.5, &c1, &c2);
cubic_approximation (&c1, &cc1);
cubic_approximation (&c2, &cc2);
return gsk_conic_curve_decompose_or_add (&c1, &cc1, tolerance, add_curve_func, user_data) &&
gsk_conic_curve_decompose_or_add (&c2, &cc2, tolerance, add_curve_func, user_data);
}
}
static gboolean
gsk_conic_curve_decompose_curve (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data)
{
GskCurve c;
cubic_approximation (curve, &c);
return gsk_conic_curve_decompose_or_add (curve, &c, tolerance, add_curve_func, user_data);
}
static gskpathop
gsk_conic_curve_pathop (const GskCurve *curve)
{
@@ -1035,6 +1153,7 @@ static const GskCurveClass GSK_CONIC_CURVE_CLASS = {
gsk_conic_curve_split,
gsk_conic_curve_segment,
gsk_conic_curve_decompose,
gsk_conic_curve_decompose_curve,
gsk_conic_curve_pathop,
gsk_conic_curve_get_start_point,
gsk_conic_curve_get_end_point,
@@ -1128,6 +1247,15 @@ gsk_curve_decompose (const GskCurve *curve,
return get_class (curve->op)->decompose (curve, tolerance, add_line_func, user_data);
}
gboolean
gsk_curve_decompose_curve (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data)
{
return get_class (curve->op)->decompose_curve (curve, tolerance, add_curve_func, user_data);
}
gskpathop
gsk_curve_pathop (const GskCurve *curve)
{

7
gsk/gskcurveprivate.h
View File

@@ -83,6 +83,9 @@ typedef gboolean (* GskCurveAddLineFunc) (const graphene_point_t *from,
float to_progress,
gpointer user_data);
typedef gboolean (* GskCurveAddCurveFunc) (const graphene_point_t points[4],
gpointer user_data);
void gsk_curve_init (GskCurve *curve,
gskpathop op);
void gsk_curve_init_foreach (GskCurve *curve,
@@ -109,6 +112,10 @@ gboolean gsk_curve_decompose (const GskCurve
float tolerance,
GskCurveAddLineFunc add_line_func,
gpointer user_data);
gboolean gsk_curve_decompose_curve (const GskCurve *curve,
float tolerance,
GskCurveAddCurveFunc add_curve_func,
gpointer user_data);
gskpathop gsk_curve_pathop (const GskCurve *curve);
#define gsk_curve_builder_to(curve, builder) gsk_path_builder_pathop_to ((builder), gsk_curve_pathop (curve))
const graphene_point_t *gsk_curve_get_start_point (const GskCurve *curve);