public static SKMatrix CaculateOneFingerDraggedMatrix(SKPoint prevPoint, SKPoint curPoint, SKPoint pivotPoint, TouchManipulationMode mode)
{
if (mode == TouchManipulationMode.None)
{
return(SKMatrix.CreateIdentity());
}
SKMatrix touchMatrix = SKMatrix.CreateIdentity();
SKPoint delta = curPoint - prevPoint;
if (mode == TouchManipulationMode.ScaleDualRotate) // One-finger rotation
{
SKPoint oldVector = prevPoint - pivotPoint;
SKPoint newVector = curPoint - pivotPoint;
// Avoid rotation if fingers are too close to center
if (Magnitude(newVector) > 25 && Magnitude(oldVector) > 25)
{
float prevAngle = (float)Math.Atan2(oldVector.Y, oldVector.X);
float newAngle = (float)Math.Atan2(newVector.Y, newVector.X);
// Calculate rotation matrix
float angle = newAngle - prevAngle;
touchMatrix = SKMatrix.CreateRotation(angle, pivotPoint.X, pivotPoint.Y);
// Effectively rotate the old vector
float magnitudeRatio = Magnitude(oldVector) / Magnitude(newVector);
oldVector.X = magnitudeRatio * newVector.X;
oldVector.Y = magnitudeRatio * newVector.Y;
// Recalculate delta
delta = newVector - oldVector;
}
}
// Multiply the rotation matrix by a translation matrix
touchMatrix = touchMatrix.PostConcat(SKMatrix.CreateTranslation(delta.X, delta.Y));
return(touchMatrix);
}
public static SKMatrix CaculateTwoFingerDraggedMatrix(SKPoint prevPoint, SKPoint curPoint, SKPoint pivotPoint, TouchManipulationMode mode)
{
SKMatrix touchMatrix = SKMatrix.CreateIdentity();
SKPoint oldVector = prevPoint - pivotPoint;
SKPoint newVector = curPoint - pivotPoint;
if (mode == TouchManipulationMode.ScaleRotate ||
mode == TouchManipulationMode.ScaleDualRotate)
{
// Find angles from pivot point to touch points
float oldAngle = (float)Math.Atan2(oldVector.Y, oldVector.X);
float newAngle = (float)Math.Atan2(newVector.Y, newVector.X);
// Calculate rotation matrix
float angle = newAngle - oldAngle;
touchMatrix = SKMatrix.CreateRotation(angle, pivotPoint.X, pivotPoint.Y);
// Effectively rotate the old vector
float magnitudeRatio = Magnitude(oldVector) / Magnitude(newVector);
oldVector.X = magnitudeRatio * newVector.X;
oldVector.Y = magnitudeRatio * newVector.Y;
}
float scaleX = 1;
float scaleY = 1;
if (mode == TouchManipulationMode.AnisotropicScale)
{
scaleX = newVector.X / oldVector.X;
scaleY = newVector.Y / oldVector.Y;
}
else if (mode == TouchManipulationMode.IsotropicScale ||
mode == TouchManipulationMode.ScaleRotate ||
mode == TouchManipulationMode.ScaleDualRotate)
{
scaleX = scaleY = Magnitude(newVector) / Magnitude(oldVector);
}
if (!float.IsNaN(scaleX) && !float.IsInfinity(scaleX) &&
!float.IsNaN(scaleY) && !float.IsInfinity(scaleY))
{
touchMatrix = touchMatrix.PostConcat(SKMatrix.CreateScale(scaleX, scaleY, pivotPoint.X, pivotPoint.Y));
}
return(touchMatrix);
}