Replace STU dewarp spline initialization method by STEX version

* research #2

Author: zvezdochiot

src/core/filters/deskew/DewarpingView.cpp

@@ -126,11 +126,17 @@ DewarpingView::~DewarpingView()
 void
 DewarpingView::initNewSpline(XSpline& spline, QPointF const& p1, QPointF const& p2)
 {
+    int const num_points = 4;
     QLineF const line(p1, p2);
     spline.appendControlPoint(line.p1(), 0);
-    spline.appendControlPoint(line.pointAt(1.0/4.0), 1);
-    spline.appendControlPoint(line.pointAt(2.0/4.0), 1);
-    spline.appendControlPoint(line.pointAt(3.0/4.0), 1);
+    if (num_points > 2)
+    {
+        for (int i = 1; i < (num_points - 1); i++)
+        {
+            double frac = (double) i / (num_points - 1);
+            spline.appendControlPoint(line.pointAt(frac), 1);
+        }
+    }
     spline.appendControlPoint(line.p2(), 0);
 }