Implemented transformAsBase() function for KisAlgebra2D

krita/image/kis_algebra_2d.cpp

@@ -55,4 +55,26 @@ void KRITAIMAGE_EXPORT adjustIfOnPolygonBoundary(const QPolygonF &poly, int poly
     }
 }
 
+QPointF KRITAIMAGE_EXPORT transformAsBase(const QPointF &pt, const QPointF &base1, const QPointF &base2) {
+    qreal len1 = norm(base1);
+    if (len1 < 1e-5) return pt;
+    qreal sin1 = base1.y() / len1;
+    qreal cos1 = base1.x() / len1;
+
+    qreal len2 = norm(base2);
+    if (len2 < 1e-5) return QPointF();
+    qreal sin2 = base2.y() / len2;
+    qreal cos2 = base2.x() / len2;
+
+    qreal sinD = sin2 * cos1 - cos2 * sin1;
+    qreal cosD = cos1 * cos2 + sin1 * sin2;
+    qreal scaleD = len2 / len1;
+
+    QPointF result;
+    result.rx() = scaleD * (pt.x() * cosD - pt.y() * sinD);
+    result.ry() = scaleD * (pt.x() * sinD + pt.y() * cosD);
+
+    return result;
+}
+
 }

krita/image/kis_algebra_2d.h

@@ -121,6 +121,14 @@ bool isInRange(T x, T a, T b) {
 
 void KRITAIMAGE_EXPORT adjustIfOnPolygonBoundary(const QPolygonF &poly, int polygonDirection, QPointF *pt);
 
+/**
+ * Let \p pt, \p base1 are two vectors. \p base1 is uniformly scaled
+ * and then rotated into \p base2 using transformation matrix S *
+ * R. The function applies the same transformation to \pt and returns
+ * the result.
+ **/
+QPointF transformAsBase(const QPointF &pt, const QPointF &base1, const QPointF &base2);
+
 }
 
 #endif /* __KIS_ALGEBRA_2D_H */

krita/image/tests/kis_cage_transform_worker_test.cpp

@@ -203,5 +203,52 @@ void KisCageTransformWorkerTest::testUnityGreenCoordinates()
     }
 }
 
+#include "kis_algebra_2d.h"
+
+void KisCageTransformWorkerTest::testTransformAsBase()
+{
+    QPointF t(1.0, 0.0);
+    QPointF b1(1.0, 0.0);
+    QPointF b2(2.0, 0.0);
+    QPointF result;
+
+
+    t = QPointF(1.0, 0.0);
+    b1 = QPointF(1.0, 0.0);
+    b2 = QPointF(2.0, 0.0);
+    result = KisAlgebra2D::transformAsBase(t, b1, b2);
+    QCOMPARE(result, QPointF(2.0, 0.0));
+
+    t = QPointF(1.0, 0.0);
+    b1 = QPointF(1.0, 0.0);
+    b2 = QPointF(0.0, 1.0);
+    result = KisAlgebra2D::transformAsBase(t, b1, b2);
+    QCOMPARE(result, QPointF(0.0, 1.0));
+
+    t = QPointF(1.0, 0.0);
+    b1 = QPointF(1.0, 0.0);
+    b2 = QPointF(0.0, 2.0);
+    result = KisAlgebra2D::transformAsBase(t, b1, b2);
+    QCOMPARE(result, QPointF(0.0, 2.0));
+
+    t = QPointF(0.0, 1.0);
+    b1 = QPointF(1.0, 0.0);
+    b2 = QPointF(2.0, 0.0);
+    result = KisAlgebra2D::transformAsBase(t, b1, b2);
+    QCOMPARE(result, QPointF(0.0, 2.0));
+
+    t = QPointF(0.0, 1.0);
+    b1 = QPointF(1.0, 0.0);
+    b2 = QPointF(0.0, 1.0);
+    result = KisAlgebra2D::transformAsBase(t, b1, b2);
+    QCOMPARE(result, QPointF(-1.0, 0.0));
+
+    t = QPointF(0.0, 1.0);
+    b1 = QPointF(1.0, 0.0);
+    b2 = QPointF(0.0, 2.0);
+    result = KisAlgebra2D::transformAsBase(t, b1, b2);
+    QCOMPARE(result, QPointF(-2.0, 0.0));
+}
+
 
 QTEST_KDEMAIN(KisCageTransformWorkerTest, GUI)

krita/image/tests/kis_cage_transform_worker_test.h

@@ -34,6 +34,8 @@ private slots:
     void testCageCounterclockwiseUnity();
 
     void testUnityGreenCoordinates();
+
+    void testTransformAsBase();
 };
 
 #endif /* __KIS_CAGE_TRANSFORM_WORKER_TEST_H */