第五章：Transforms
Affine Transforms
CGAffineTransform是二维的
Creating a CGAffineTransform
主要有三种变化方法
旋转：
CGAffineTransformMakeRotation(CGFloat angle)
缩放：
CGAffineTransformMakeScale(CGFloat sx, CGFloat sy)
移动：
CGAffineTransformMakeTranslation(CGFloat tx, CGFloat ty)
样例5.1 CGAffineTransformMakeRotation
源代码在这里下载：http://www.informit.com/title/9780133440751
@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIView *layerView;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees
CGAffineTransform transform = CGAffineTransformMakeRotation(M_PI_4);
self.layerView.layer.affineTransform = transform;
}
@end
改动 CGAffineTransformMakeScale
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees
CGAffineTransform transform = CGAffineTransformMakeScale(0.5, 0.5);
self.layerView.layer.affineTransform = transform;
}
改动 CGAffineTransformMakeTranslation
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees
CGAffineTransform transform = CGAffineTransformMakeTranslation(-50.0, 30.0);
self.layerView.layer.affineTransform = transform;
}
Combining Transforms
方法1：使用CGAffineTransformConcat
继续改动样例5.1
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees
CGAffineTransform transform1 = CGAffineTransformMakeRotation(M_PI_4);
CGAffineTransform transform2 = CGAffineTransformMakeScale(0.5, 0.5);
CGAffineTransform transform = CGAffineTransformConcat(transform1, transform2);
self.layerView.layer.affineTransform = transform;
}
方法2：
CGAffineTransformRotate(CGAffineTransform t, CGFloat angle)
CGAffineTransformScale(CGAffineTransform t, CGFloat sx, CGFloat sy)
CGAffineTransformTranslate(CGAffineTransform t, CGFloat tx, CGFloat ty)
CGAffineTransformScale(CGAffineTransform t, CGFloat sx, CGFloat sy)
CGAffineTransformTranslate(CGAffineTransform t, CGFloat tx, CGFloat ty)
和前面的CGAffineTransformMakeRotation函数同样，也能够混用
CGAffineTransform t能够使用CGAffineTransformIdentity函数初始化
样例5.2
@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIView *layerView;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//create a new transform
CGAffineTransform transform = CGAffineTransformIdentity;
//scale by 50%
transform = CGAffineTransformScale(transform, 0.5, 0.5);
//rotate by 30 degrees
transform = CGAffineTransformRotate(transform, M_PI / 180.0 * 30.0);
//translate by 200 points
transform = CGAffineTransformTranslate(transform, 200, 0);
//apply transform to layer
self.layerView.layer.affineTransform = transform;
}
@end
以下记几个特殊值
1. 首先要知道函数 CGAffineTransformIdentity 初始化的结果
2. 左右翻转
CGAffineTransformMake(-1,0,0,1,0,0);
3. 以右边为轴向右翻转
CGAffineTransformMake(-1,0,0,1,self.layerView.frame.size.width,0);
CGAffineTransformMake(1,0,0, -1,0,0);
5. 以底边为轴向下翻转
CGAffineTransformMake(1,0,0, -1,0,self.layerView.frame.size.height);
6. 转180°
CGAffineTransformMake(-1,0,0, -1,0,0);
7. 样例5.3。向右斜拉
CGAffineTransformMake(1,0, -1,1,0,0);
代码：
@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIView *layerView;
@end
@implementation ViewController
CGAffineTransform CGAffineTransformMakeShear(CGFloat x, CGFloat y)
{
CGAffineTransform transform = CGAffineTransformIdentity;
transform.c = -x;
transform.b = y;
return transform;
}
- (void)viewDidLoad
{
[super viewDidLoad];
//shear the layer at a 45-degree angle
self.layerView.layer.affineTransform = CGAffineTransformMakeShear(1, 0);
}
@end
8. 样例5.3，向左斜拉
CGAffineTransformMake(1, 0,1, 1, 0, 0);
3D Transforms
相似CGAffineTransform，CATransform3D是三维的
CATransform3D又是一个结构。他有自己的一个公式。能够进行套用。
struct CATransform3D
{
CGFloat m11(x缩放), m12(y切变), m13(旋转), m14( );
CGFloat m21(x切变), m22(y缩放), m23( ), m24( );
CGFloat m31(旋转), m32( ), m33( ), m34(透视效果。要操作的这个对象要有旋转的角度，否则没有效果。
正直/负值都有意义);
CGFloat m41(x平移), m42(y平移), m43(z平移), m44( );
};
同样有三种变换方法
旋转：
CATransform3DMakeRotation(CGFloat angle, CGFloat x, CGFloat y, CGFloat z)
首先要先清楚x，y，z是什么
{x, y, z}组成的向量就是旋转要使用的轴，angle是旋转角度
例：原图
向X轴旋转45度。 向Y轴旋转45度。 向Z轴旋转45度。
向 X轴，Y轴都旋转45度，就是沿着对角线旋转。
缩放：
CATransform3DMakeScale(CGFloat sx, CGFloat sy, CGFloat sz)
sx：X轴缩放，代表一个缩放比例，一般都是0 ---1之间的数字。
sy：Y轴缩放。
sz：总体比例变换时，也就是m11(sx) == m22(sy)时。若m33(sz)>1，图形总体缩小。
若0 < m33(sz) < 1，图形总体放大，
若m33(sz) < 0。发生关于原点的对称等比变换。
当sx = 1，sy =1时。如图：
当sx = 0.5。sy =0.5时。
如图：
变换：
CATransform3DMakeTranslation(Gloat tx, CGFloat ty, CGFloat tz)
t' = [1 0 0 0; 0 1 0 0; 0 0 1 0; tx ty tz 1]
1 0 0 0
0 1 0 0
0 0 1 0
tx ty tz 1
竖起来看相应前面的数据结构就非常明显了。
tx：X轴偏移位置。往下为正数。
ty：Y轴偏移位置。往右为正数。
tz：Z轴偏移位置。往外为正数。
能够通过直接改动数据结构。来设置变换效果
struct CATransform3D
{
CGFloat m11, m12, m13, m14。
CGFloat m21, m22, m23, m24；
CGFloat m31, m32, m33, m34。
CGFloat m41, m42, m43, m44；
}
CATransform3D transform = CATransform3DMakeRotation(M_PI_4, 0, 1, 0);
transform.m11 = 2;
或者改动键值
[myLayer setValue:[NSNumber numberWithInt:0] forKeyPath:@"transform.rotation.x"];
样例5.4
@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIView *layerView;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees along the Y axis
CATransform3D transform = CATransform3DMakeRotation(M_PI_4, 0, 1, 0);
self.layerView.layer.transform = transform;
}
@end
改动样例5.4，改动自http://lepetit-prince.net/ios/?p=451
#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
@interface ViewController ()
{
BOOL front;
}
@property (nonatomic, weak) IBOutlet UIView *layerView;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
front = YES;
self.layerView.layer.contents = (__bridge id)([UIImage imageNamed:@"front.png"].CGImage);
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
[UIView animateWithDuration:0.5 animations:^{
self.layerView.layer.transform = CATransform3DMakeRotation(M_PI * 0.5, 0.0f, 1.0f, 0.0f);
} completion:^(BOOL finished) {
self.layerView.layer.transform = CATransform3DMakeRotation(M_PI * 1.5, 0.0f, 1.0f, 0.0f);
self.layerView.layer.contents = front ? (__bridge id)([UIImage imageNamed:@"back.png"].CGImage) : (__bridge id)([UIImage imageNamed:@"front.png"].CGImage);
[UIView animateWithDuration:0.5 animations:^{
self.layerView.layer.transform = CATransform3DMakeRotation(M_PI * 2, 0.0f, 1.0f, 0.0f);
} completion:^(BOOL finished) {
front = !front;
}];
}];
}
@end
Perspective Projection
前面提到过m34(透视效果，要操作的这个对象要有旋转的角度，否则没有效果。
正直
/负值都有意义)样例5.5
@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIView *layerView;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//create a new transform
CATransform3D transform = CATransform3DIdentity;
//apply perspective
transform.m34 = - 1.0 / 500.0;
//rotate by 45 degrees along the Y axis
transform = CATransform3DRotate(transform, M_PI_4, 0, 1, 0);
//apply to layer
self.layerView.layer.transform = transform;
}
@end
假设改动凝视掉旋转，看看会有什么结果
//rotate by 45 degrees along the Y axis
//transform = CATransform3DRotate(transform, M_PI_4, 0, 1, 0);
样例是用的透视场景是±1.0/d，d镜头到景物的距离。取值500~1000效果最好，±代表方向
The Vanishing Point
当景物慢慢远离镜头时。随着越来越小终于聚集到一点就是Vanishing Point(灭点)
通常情况灭点是在视图的正中心，或者在包括全部景物范围的中心。
Core Animation把灭点定义在anchorPoint，所以在变换前须要确定anchorPoint，
尤其须要注意，3D变换时最好确保同一视图内的全部layey有同样的灭点
The sublayerTransform Property
假设你有多个View或Layer有同样的3D变换。就能够使用sublayerTransform，
sublayerTransform也是CATransform3D，仅仅有sublayers才会响应。
默认值是Identity Transform(CATransform3DIdentity)
样例5.6
@interface ViewController ()
@property (nonatomic, weak) IBOutlet UIView *containerView;
@property (nonatomic, weak) IBOutlet UIView *layerView1;
@property (nonatomic, weak) IBOutlet UIView *layerView2;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//apply perspective transform to container
CATransform3D perspective = CATransform3DIdentity;
perspective.m34 = - 1.0 / 500.0;
self.containerView.layer.sublayerTransform = perspective;
//rotate layerView1 by 45 degrees along the Y axis
CATransform3D transform1 = CATransform3DMakeRotation(M_PI_4, 0, 1, 0);
self.layerView1.layer.transform = transform1;
//rotate layerView2 by 45 degrees along the Y axis
CATransform3D transform2 = CATransform3DMakeRotation(-M_PI_4, 0, 1, 0);
self.layerView2.layer.transform = transform2;
}
@end
我们挪动一下xib里的图片位置：
再看结果
恢复xib文件，并改动代码
- (void)viewDidLoad
{
[super viewDidLoad];
//apply perspective transform to container
// CATransform3D perspective = CATransform3DIdentity;
// perspective.m34 = - 1.0 / 500.0;
// self.containerView.layer.sublayerTransform = perspective;
//apply perspective
CATransform3D transform1 = CATransform3DIdentity;
transform1.m34 = - 1.0 / 500.0;
transform1 = CATransform3DRotate(transform1, M_PI_4, 0, 1, 0);
self.layerView1.layer.transform = transform1;
//rotate layerView2 by 45 degrees along the Y axis
CATransform3D transform2 = CATransform3DIdentity;
transform2.m34 = - 1.0 / 500.0;
transform2 = CATransform3DRotate(transform2, -M_PI_4, 0, 1, 0);
self.layerView2.layer.transform = transform2;
}
结果和最初一样，但再次改动xib文件。挪动图片看结果，比較未改代码时的效果
大家发现设置sublayerTransform的优点了吗
1. 能够一次设置全部subLayer的变换效果
2. Vanishing Point(灭点)被同一时候设置在container layer即父图层的中心，这就意味着不管你怎么
改动subLayer的position或frame，它们都会保持一个同样的灭点。
Backfaces
样例5.4。我们设置的是旋转M_PI_4(45°)，改为M_PI(180°)
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees along the Y axis
CATransform3D transform = CATransform3DMakeRotation(M_PI, 0, 1, 0);
self.layerView.layer.transform = transform;
}
翻到了layer背面，显示的是原图像的镜像图。由此可见layer是双面的。而且两面都被描绘了。
因此我们会想到，为什么要浪费GPU去描绘我们看不见的部分呢。
CALayer的另外一个属性
doubleSided能够解决问题。
在刚才改动过的样例5.4的代码中添加doubleSided设置
- (void)viewDidLoad
{
[super viewDidLoad];
//rotate the layer 45 degrees along the Y axis
CATransform3D transform = CATransform3DMakeRotation(M_PI, 0, 1, 0);
self.layerView.layer.transform = transform;
self.layerView.layer.doubleSided = NO;
}
图像没有了
Layer Flattening
自己看样例吧。样例5.7和5.8
Solid Objects
也自己看样例吧，样例5.9和5.10