* Added bezier routines.

[scdataviz] / graph.c

diff --git a/graph.c b/graph.c
index 1b0f468..423ff84 100644 (file)
--- a/graph.c
+++ b/graph.c
@@ -125,10 +125,10 @@ static void linear_interpolate(gpointer data, gpointer user_data) {
   struct cxt *cxt = user_data;
   struct graph_point *p3 = data;
   if(cxt->p0 != NULL) {
-    double p1_x = (p3->x - cxt->p0->x)/3.0;
-    double p1_y = (p3->y - cxt->p0->y)/3.0;
-    double p2_x = (p3->x + 2*cxt->p0->x)/3.0;
-    double p2_y = (p3->y + 2*cxt->p0->y)/3.0;
+    double p1_x = (p3->x + 2*cxt->p0->x)/3.0;
+    double p1_y = (p3->y + 2*cxt->p0->y)/3.0;
+    double p2_x = (2*p3->x + cxt->p0->x)/3.0;
+    double p2_y = (2*p3->y + cxt->p0->y)/3.0;
     graph_add_line(cxt->graph, cxt->p0->x, cxt->p0->y, p1_x, p1_y, p2_x, p2_y, p3->x, p3->y);
   }
   cxt->p0 = p3;
@@ -140,3 +140,13 @@ void graph_add_linear_connectors(Graph* graph) {
   cxt.p0 = NULL;
   g_ptr_array_foreach(graph->points, &linear_interpolate, &cxt);
 }
+
+void graph_bezier_linear_to_cubic(double x0, double x3, double *x1, double *x2) {
+  *x1 = (x3 + 2.0*x0)/3.0;
+  *x2 = (2.0*x3 + x0)/3.0;
+}
+
+void graph_bezier_qudratic_to_cubic(double x0, double x3, double *x1, double *x2) {
+  *x2 = (x3 - x0)/3.0 + (*x1);
+  *x1 = (x0 - 3.0*(*x1))/2.0;
+}