本示例不使用手势识别器，而是直接计算变换矩阵。它还可以正确处理一到两个手指的转换。
class PincherView: UIView {
override var bounds :CGRect {
willSet(newBounds) {
oldBounds = self.bounds
} didSet {
self.imageLayer.position = ┼self.bounds
self._adjustScaleForBoundsChange()
}
}
var oldBounds :CGRect
var touch₁ :UITouch?
var touch₂ :UITouch?
var p₁ :CGPoint? // point 1 in image coordiate system
var p₂ :CGPoint? // point 2 in image coordinate system
var p₁ʹ :CGPoint? // point 1 in view coordinate system
var p₂ʹ :CGPoint? // point 2 in view coordinate system
var image :UIImage? {
didSet {self._reset()}
}
var imageLayer :CALayer
var imageTransform :CGAffineTransform {
didSet {
self.backTransform = self.imageTransform.inverted()
self.imageLayer.transform = CATransform3DMakeAffineTransform(self.imageTransform)
}
}
var backTransform :CGAffineTransform
var solutionMatrix :HXMatrix?
required init?(coder aDecoder: NSCoder) {
self.oldBounds = CGRect.zero
let layer = CALayer();
self.imageLayer = layer
self.imageTransform = CGAffineTransform.identity
self.backTransform = CGAffineTransform.identity
super.init(coder: aDecoder)
self.oldBounds = self.bounds
self.isMultipleTouchEnabled = true
self.layer.addSublayer(layer)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
let pʹ = touch.location(in: self).applying(self._backNormalizeTransform())
let p = pʹ.applying(self.backTransform)
if self.touch₁ == nil {
self.touch₁ = touch
self.p₁ʹ = pʹ
self.p₁ = p
} else if self.touch₂ == nil {
self.touch₂ = touch
self.p₂ʹ = pʹ
self.p₂ = p
}
}
self.solutionMatrix = self._computeSolutionMatrix()
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
let pʹ = touch.location(in: self).applying(self._backNormalizeTransform())
if self.touch₁ == touch {
self.p₁ʹ = pʹ
} else if self.touch₂ == touch {
self.p₂ʹ = pʹ
}
}
CATransaction.begin()
CATransaction.setValue(true, forKey:kCATransactionDisableActions)
// Whether you're using 1 finger or 2 fingers
if let q₁ʹ = self.p₁ʹ, let q₂ʹ = self.p₂ʹ {
self.imageTransform = self._computeTransform(q₁ʹ, q₂ʹ)
} else if let q₁ʹ = (self.p₁ʹ != nil ? self.p₁ʹ : self.p₂ʹ) {
self.imageTransform = self._computeTransform(q₁ʹ, CGPoint(x:q₁ʹ.x + 10, y:q₁ʹ.y + 10))
}
CATransaction.commit()
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
if self.touch₁ == touch {
self.touch₁ = nil
self.p₁ = nil
self.p₁ʹ = nil
} else if self.touch₂ == touch {
self.touch₂ = nil
self.p₂ = nil
self.p₂ʹ = nil
}
}
self.solutionMatrix = self._computeSolutionMatrix()
}
//MARK: Private Methods
private func _reset() {
guard
let image = self.image,
let cgimage = image.cgImage else {
return
}
let r = CGRect(x:0, y:0, width:cgimage.width, height:cgimage.height)
imageLayer.contents = cgimage;
imageLayer.bounds = r
imageLayer.position = ┼self.bounds
self.imageTransform = self._initialTransform()
}
private func _normalizeTransform() -> CGAffineTransform {
let center = ┼self.bounds
return CGAffineTransform(translationX: center.x, y: center.y)
}
private func _backNormalizeTransform() -> CGAffineTransform {
return self._normalizeTransform().inverted();
}
private func _initialTransform() -> CGAffineTransform {
guard let image = self.image, let cgimage = image.cgImage else {
return CGAffineTransform.identity;
}
let r = CGRect(x:0, y:0, width:cgimage.width, height:cgimage.height)
let s = r.scaleIn(rect: self.bounds)
return CGAffineTransform(scaleX: s, y: s)
}
private func _adjustScaleForBoundsChange() {
guard let image = self.image, let cgimage = image.cgImage else {
return
}
let r = CGRect(x:0, y:0, width:cgimage.width, height:cgimage.height)
let oldIdeal = r.scaleAndCenterIn(rect: self.oldBounds)
let newIdeal = r.scaleAndCenterIn(rect: self.bounds)
let s = newIdeal.height / oldIdeal.height
self.imageTransform = self.imageTransform.scaledBy(x: s, y: s)
}
private func _computeSolutionMatrix() -> HXMatrix? {
if let q₁ = self.p₁, let q₂ = self.p₂ {
return _computeSolutionMatrix(q₁, q₂)
} else if let q₁ = self.p₁, let q₁ʹ = self.p₁ʹ {
let q₂ = CGPoint(x: q₁ʹ.x + 10, y: q₁ʹ.y + 10).applying(self.backTransform)
return _computeSolutionMatrix(q₁, q₂)
} else if let q₂ = self.p₂, let q₂ʹ = self.p₂ʹ {
let q₁ = CGPoint(x: q₂ʹ.x + 10, y: q₂ʹ.y + 10).applying(self.backTransform)
return _computeSolutionMatrix(q₂, q₁)
}
return nil
}
private func _computeSolutionMatrix(_ q₁:CGPoint, _ q₂:CGPoint) -> HXMatrix {
let x₁ = Double(q₁.x)
let y₁ = Double(q₁.y)
let x₂ = Double(q₂.x)
let y₂ = Double(q₂.y)
let A = HXMatrix(rows: 4, columns: 4, values:[
x₁, -y₁, 1, 0,
y₁, x₁, 0, 1,
x₂, -y₂, 1, 0,
y₂, x₂, 0, 1
])
return A.inverse()
}
private func _computeTransform(_ q₁ʹ:CGPoint, _ q₂ʹ:CGPoint) -> CGAffineTransform {
guard let solutionMatrix = self.solutionMatrix else {
return CGAffineTransform.identity
}
let B = HXMatrix(rows: 4, columns: 1, values: [
Double(q₁ʹ.x),
Double(q₁ʹ.y),
Double(q₂ʹ.x),
Double(q₂ʹ.y)
])
let C = solutionMatrix ⋅ B
let U = CGFloat(C[0,0])
let V = CGFloat(C[1,0])
let tx = CGFloat(C[2,0])
let ty = CGFloat(C[3,0])
var t :CGAffineTransform = CGAffineTransform.identity
t.a = U; t.b = V
t.c = -V; t.d = U
t.tx = tx; t.ty = ty
return t
}
}