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authorBehdad Esfahbod <behdad@gnome.org>2007-10-20 07:51:02 +0000
committerBehdad Esfahbod <behdad@src.gnome.org>2007-10-20 07:51:02 +0000
commit916a3b3ca81747437b17bbd9e7f2e6876f24b78a (patch)
tree66fada5962c1323f333ac33c43c788d85fde1b53 /examples/cairotwisted.c
parent19679486980a281d865b0050bd15982629ccbb70 (diff)
downloadpango-916a3b3ca81747437b17bbd9e7f2e6876f24b78a.tar.gz
Implement bezier curve length function that flattens the curve and sum the
2007-10-20 Behdad Esfahbod <behdad@gnome.org> * examples/cairotwisted.c (curve_length): Implement bezier curve length function that flattens the curve and sum the length of straight lines approximating it. svn path=/trunk/; revision=2451
Diffstat (limited to 'examples/cairotwisted.c')
-rw-r--r--examples/cairotwisted.c76
1 files changed, 69 insertions, 7 deletions
diff --git a/examples/cairotwisted.c b/examples/cairotwisted.c
index 93fa5164..180cd447 100644
--- a/examples/cairotwisted.c
+++ b/examples/cairotwisted.c
@@ -20,6 +20,54 @@ two_points_distance (cairo_path_data_t *a, cairo_path_data_t *b)
return sqrt (dx * dx + dy * dy);
}
+static double
+curve_length (double x0, double y0,
+ double x1, double y1,
+ double x2, double y2,
+ double x3, double y3)
+{
+ cairo_surface_t *surface;
+ cairo_t *cr;
+ cairo_path_t *path;
+ cairo_path_data_t *data, current_point;
+ int i;
+ double length;
+
+ surface = cairo_image_surface_create (CAIRO_FORMAT_A8, 0, 0);
+ cr = cairo_create (surface);
+ cairo_surface_destroy (surface);
+
+ cairo_move_to (cr, x0, y0);
+ cairo_curve_to (cr, x1, y1, x2, y2, x3, y3);
+
+ length = 0;
+ path = cairo_copy_path_flat (cr);
+ for (i=0; i < path->num_data; i += path->data[i].header.length) {
+ data = &path->data[i];
+ switch (data->header.type) {
+
+ case CAIRO_PATH_MOVE_TO:
+ current_point = data[1];
+ break;
+
+ case CAIRO_PATH_LINE_TO:
+ length += two_points_distance (&current_point, &data[1]);
+ current_point = data[1];
+ break;
+
+ default:
+ case CAIRO_PATH_CURVE_TO:
+ case CAIRO_PATH_CLOSE_PATH:
+ g_assert_not_reached ();
+ }
+ }
+ cairo_path_destroy (path);
+
+ cairo_destroy (cr);
+
+ return length;
+}
+
typedef double parametrization_t;
static parametrization_t *
@@ -43,20 +91,22 @@ parametrize_path (cairo_path_t *path)
current_point = data[1];
break;
case CAIRO_PATH_CURVE_TO:
- /*
+ /* naive curve-length, treating bezier as three line segments:
+ parametrization[i] = two_points_distance (&current_point, &data[1])
+ + two_points_distance (&data[1], &data[2])
+ + two_points_distance (&data[2], &data[3]);
+ */
parametrization[i] = curve_length (current_point.point.x, current_point.point.x,
data[1].point.x, data[1].point.y,
data[2].point.x, data[2].point.y,
data[3].point.x, data[3].point.y);
- */
- parametrization[i] = two_points_distance (&current_point, &data[1]);
- parametrization[i] += two_points_distance (&data[1], &data[2]);
- parametrization[i] += two_points_distance (&data[2], &data[3]);
current_point = data[3];
break;
case CAIRO_PATH_CLOSE_PATH:
break;
+ default:
+ g_assert_not_reached ();
}
}
@@ -96,6 +146,8 @@ _fancy_cairo_stroke (cairo_t *cr, cairo_bool_t preserve)
break;
case CAIRO_PATH_CLOSE_PATH:
break;
+ default:
+ g_assert_not_reached ();
}
}
cairo_stroke (cr);
@@ -125,6 +177,8 @@ _fancy_cairo_stroke (cairo_t *cr, cairo_bool_t preserve)
case CAIRO_PATH_CLOSE_PATH:
cairo_rel_line_to (cr, 0, 0);
break;
+ default:
+ g_assert_not_reached ();
}
}
cairo_rel_line_to (cr, 0, 0);
@@ -148,6 +202,8 @@ _fancy_cairo_stroke (cairo_t *cr, cairo_bool_t preserve)
case CAIRO_PATH_CLOSE_PATH:
cairo_close_path (cr);
break;
+ default:
+ g_assert_not_reached ();
}
}
cairo_stroke (cr);
@@ -192,6 +248,8 @@ transform_path (cairo_path_t *path, transform_point_func_t f, void *closure)
break;
case CAIRO_PATH_CLOSE_PATH:
break;
+ default:
+ g_assert_not_reached ();
}
}
}
@@ -229,6 +287,8 @@ point_on_path (parametrized_path_t *param,
break;
case CAIRO_PATH_CLOSE_PATH:
break;
+ default:
+ g_assert_not_reached ();
}
}
data = &path->data[i];
@@ -282,6 +342,8 @@ point_on_path (parametrized_path_t *param,
break;
case CAIRO_PATH_CLOSE_PATH:
break;
+ default:
+ g_assert_not_reached ();
}
}
@@ -357,10 +419,10 @@ draw_twisted (cairo_t *cr,
cairo_save (cr);
/* Decrease tolerance a bit, since it's going to be magnified */
- cairo_set_tolerance (cr, 0.05);
+ cairo_set_tolerance (cr, 0.1);
path = cairo_copy_path_flat (cr);
- /*path = cairo_copy_path (cr);*/
+/*path = cairo_copy_path (cr);*/
cairo_new_path (cr);