学习文章
CATransform3D vs. CGAffineTransform?
解释
CGAffineTransform
是用于2D层面的,操作 NSView, UIView或者其他 2D Core Graphics 元素的.
CATransform3D
是 Core Animation的结构体,是用来做更复杂的关于 CALayer 的3D操作.CATransform3D 有着与 OpenGL 模型视图矩阵相同的内部结构,原因在于 Core Animation 是建立在 OpenGL 之上的, CALayer是 OpenGL 结构的一种封装.
CGAffineTransform
struct CGAffineTransform {
CGFloat a, b, c, d;
CGFloat tx, ty;
};
创建CGAffineTransform的API
/* The identity transform: [ 1 0 0 1 0 0 ]. / const CGAffineTransform CGAffineTransformIdentity / Return the transform [ a b c d tx ty ]. */CGAffineTransform CGAffineTransformMake(CGFloat a, CGFloat b, CGFloat c, CGFloat d, CGFloat tx, CGFloat ty)
生成由Identity Transform发生相应转变的CGAffineTransform的API
/* Return a transform which translates by (tx, ty)': t' = [ 1 0 0 1 tx ty ] */CGAffineTransform CGAffineTransformMakeTranslation(CGFloat tx, CGFloat ty) /* Return a transform which scales by(sx, sy)': t' = [ sx 0 0 sy 0 0 ] / CGAffineTransform CGAffineTransformMakeScale(CGFloat sx, CGFloat sy) / Return a transform which rotates by `angle' radians: t' = [ cos(angle) sin(angle) -sin(angle) cos(angle) 0 0 ] */ CGAffineTransform CGAffineTransformMakeRotation(CGFloat angle)
指定CGAffineTransform转变的API
/* Translate t' by(tx, ty)' and return the result: t' = [ 1 0 0 1 tx ty ] * t /CGAffineTransform CGAffineTransformTranslate(CGAffineTransform t, CGFloat tx, CGFloat ty) / Scale t' by(sx, sy)' and return the result: t' = [ sx 0 0 sy 0 0 ] * t / CGAffineTransform CGAffineTransformScale(CGAffineTransform t, CGFloat sx, CGFloat sy)/ Rotate t' byangle' radians and return the result: t' = [ cos(angle) sin(angle) -sin(angle) cos(angle) 0 0 ] * t */ CGAffineTransform CGAffineTransformRotate(CGAffineTransform t, CGFloat angle)
判断CGAffineTransform的API
/* Return true if t' is the identity transform, false otherwise. */bool CGAffineTransformIsIdentity(CGAffineTransform t) /* Return true ift1' and `t2' are equal, false otherwise. */bool CGAffineTransformEqualToTransform(CGAffineTransform t1, CGAffineTransform t2)
UIView的transform属性就是一个CGAffineTransform类型的数据,默认值为CGAffineTransformIdentity。我们可以利用UIView动画让这些转变变得生动.
CATransform3D
struct CATransform3D{
CGFloat m11, m12, m13, m14;
CGFloat m21, m22, m23, m24;
CGFloat m31, m32, m33, m34;
CGFloat m41, m42, m43, m44;
};
创建CATransform3D的API
/* The identity transform: [1 0 0 0; 0 1 0 0; 0 0 1 0; 0 0 0 1]. */ const CATransform3D CATransform3DIdentity
生成由Identity Transform发生相应转变的CATransform3D的API
/* Returns a transform that translates by '(tx, ty, tz)': * t' = [1 0 0 0; 0 1 0 0; 0 0 1 0; tx ty tz 1]. / CATransform3D CATransform3DMakeTranslation (CGFloat tx, CGFloat ty, CGFloat tz) / Returns a transform that scales by `(sx, sy, sz)': * t' = [sx 0 0 0; 0 sy 0 0; 0 0 sz 0; 0 0 0 1]. /CATransform3D CATransform3DMakeScale (CGFloat sx, CGFloat sy, CGFloat sz) / Returns a transform that rotates by 'angle' radians about the vector * '(x, y, z)'. If the vector has length zero the identity transform is * returned. */ CATransform3D CATransform3DMakeRotation (CGFloat angle, CGFloat x, CGFloat y, CGFloat z)
指定CATransform3D转变的API
/* Translate 't' by '(tx, ty, tz)' and return the result: * t' = translate(tx, ty, tz) * t. / CATransform3D CATransform3DTranslate (CATransform3D t, CGFloat tx, CGFloat ty, CGFloat tz) / Scale 't' by '(sx, sy, sz)' and return the result: * t' = scale(sx, sy, sz) * t. / CATransform3D CATransform3DScale (CATransform3D t, CGFloat sx, CGFloat sy, CGFloat sz) / Rotate 't' by 'angle' radians about the vector '(x, y, z)' and return * the result. If the vector has zero length the behavior is undefined: * t' = rotation(angle, x, y, z) * t. */ CATransform3D CATransform3DRotate (CATransform3D t, CGFloat angle, CGFloat x, CGFloat y, CGFloat z)
判断CATransform3D的API
/* Returns true if 't' is the identity transform. / bool CATransform3DIsIdentity (CATransform3D t) / Returns true if 'a' is exactly equal to 'b'. / bool CATransform3DEqualToTransform (CATransform3D a, CATransform3D b) / Returns true if 't' can be represented exactly by an affine transform. */bool CATransform3DIsAffine (CATransform3D t)
与CGAffineTransform相互转换的API
/* Return a transform with the same effect as affine transform 'm'. /CATransform3D CATransform3DMakeAffineTransform (CGAffineTransform m) / Returns the affine transform represented by 't'. If 't' can not be * represented exactly by an affine transform the returned value is * undefined. */ CGAffineTransform CATransform3DGetAffineTransform (CATransform3D t)
CALayer的transform属性是是个CATransform3D类型的数据,默认值为CATransform3DIdentity。需要注意的是
,CALayer是有隐式动画的,如果你想关掉隐式动画,用
[CATransaction setDisableActions:YES];
另外,要特地说明一下矩阵中的一个参数m34,m34影响透视效果.当然,z方向上得有变化才会有透视效果,数值越大,透视效果越明显.正值/负值都有意义,导致透视方向的不同.
刘大帅（作者）原文链接：http://www.jianshu.com/p/f729f4a9b8e7著作权归作者所有.