iOS-CGAffineTransform相关函数

CGAffineTransform相关函数

CGAffineTransformMakeTranslation(width, 0.0);是改变位置的，
CGAffineTransformRotate(transform, M_PI);是旋转的。
CGAffineTransformMakeRotation(-M_PI);也是旋转的
transform = CGAffineTransformScale(transform, -1.0, 1.0);是缩放的。
view.transform = CGAffineTransformIdentity;线性代数里面讲的矩阵变换，这个是恒等变换

当你改变过一个view.transform属性或者view.layer.transform的时候需要恢复默认状态的话，记得先把他们重置可以使用view.transform = CGAffineTransformIdentity，或者view.layer.transform = CATransform3DIdentity，假设你一直不断的改变一个view.transform的属性，而每次改变之前没有重置的话，你会发现后来的改变和你想要的发生变化了，不是你真正想要的结果

Quartz转换实现的原理:Quartz把绘图分成两个部分，

    用户空间，即和设备无关，

    设备空间，

用户空间和设备空间中间存在一个转换矩阵 ： CTM

本章实质是讲解CTM

 

Quartz提供的3大功能

移动，旋转，缩放

 

演示如下，首先加载一张图片

void CGContextDrawImage (

   CGContextRef c,

   CGRect rect,

   CGImageRef image

);

移动函数

CGContextTranslateCTM (myContext, 100, 50);

 

 

 

旋转函数

include <math.h>

static inline double radians (double degrees) {return degrees * M_PI/180;}

CGContextRotateCTM (myContext, radians(–45.));

 

 

 

缩放

CGContextScaleCTM (myContext, .5, .75);

 

 

 

翻转， 两种转换合成后的效果，先把图片移动到右上角，然后旋转180度

CGContextTranslateCTM (myContext, w,h);

CGContextRotateCTM (myContext, radians(-180.));

 

 

 

组合几个动作

CGContextTranslateCTM (myContext, w/4, 0);

CGContextScaleCTM (myContext, .25,  .5);

CGContextRotateCTM (myContext, radians ( 22.));

 

 

 

 

 

CGContextRotateCTM (myContext, radians ( 22.));

CGContextScaleCTM (myContext, .25,  .5);

CGContextTranslateCTM (myContext, w/4, 0);

 

 

 

 

上面是通过直接修改当前的ctm实现3大效果，下面是通过创建Affine Transforms，然后连接ctm实现同样的3种效果

这样做的好处是可以重用这个Affine Transforms

应用Affine Transforms 到ctm的函数

void CGContextConcatCTM (

   CGContextRef c,

   CGAffineTransform transform

);

 

 

Creating Affine Transforms

移动效果

CGAffineTransform CGAffineTransformMakeTranslation (

   CGFloat tx,

   CGFloat ty

);

 

CGAffineTransform CGAffineTransformTranslate (

   CGAffineTransform t,

   CGFloat tx,

   CGFloat ty

);

 

旋转效果

CGAffineTransform CGAffineTransformMakeRotation (

   CGFloat angle

);

 

CGAffineTransform CGAffineTransformRotate (

   CGAffineTransform t,

   CGFloat angle

);

 

缩放效果

CGAffineTransform CGAffineTransformMakeScale (

   CGFloat sx,

   CGFloat sy

);

 

CGAffineTransform CGAffineTransformScale (

   CGAffineTransform t,

   CGFloat sx,

   CGFloat sy

);

 

反转效果

CGAffineTransform CGAffineTransformInvert (

   CGAffineTransform t

);

 

只对局部产生效果

CGRect CGRectApplyAffineTransform (

   CGRect rect,

   CGAffineTransform t

);

 

判断两个AffineTrans是否相等

bool CGAffineTransformEqualToTransform (

   CGAffineTransform t1,

   CGAffineTransform t2

);

 

 

 

获得Affine Transform

CGAffineTransform CGContextGetUserSpaceToDeviceSpaceTransform (

   CGContextRef c

);

 

下面的函数只起到查看的效果，比如看一下这个用户空间的点，转换到设备空间去坐标是多少

CGPoint CGContextConvertPointToDeviceSpace (

   CGContextRef c,

   CGPoint point

);

 

CGPoint CGContextConvertPointToUserSpace (

   CGContextRef c,

   CGPoint point

);

 

CGSize CGContextConvertSizeToDeviceSpace (

   CGContextRef c,

   CGSize size

);

 

CGSize CGContextConvertSizeToUserSpace (

   CGContextRef c,

   CGSize size

);

 

CGRect CGContextConvertRectToDeviceSpace (

   CGContextRef c,

   CGRect rect

);

 

CGRect CGContextConvertRectToUserSpace (

   CGContextRef c,

   CGRect rect

);

 

 

CTM真正的数学行为

这个转换矩阵其实是一个 3x3的 举证

如下图

 

 

下面举例说明几个转换运算的数学实现

x y 是原先点的坐标

下面是从用户坐标转换到设备坐标的计算公式

 

 

 

 

下面是一个identity matrix，就是输入什么坐标，出来什么坐标，没有转换

 

最终的计算结果是 x=x，y=y，  

 

 

 可以用函数判断这个矩阵是不是一个 identity matrix

bool CGAffineTransformIsIdentity (

   CGAffineTransform t

);

 

 

 

 

参考:http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_affine/dq_affine.html

- (void)willAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation  duration:(NSTimeInterval)duration

{

        

    

        if (toInterfaceOrientation == UIInterfaceOrientationPortrait)

        {

                b=YES;

                

                self.view=mainvv;

                self.view.transform = CGAffineTransformIdentity;

                self.view.transform = CGAffineTransformMakeRotation(degreesToRadian(0));

                self.view.bounds = CGRectMake(0.0, 0.0, 768.0, 1004.0);

                

        }

        else if (toInterfaceOrientation == UIInterfaceOrientationLandscapeLeft)

        {

                b=NO;

                

                self.view = self.vv;

                self.view.transform = CGAffineTransformIdentity;

                self.view.transform = CGAffineTransformMakeRotation(degreesToRadian(-90));

                self.view.bounds = CGRectMake(0.0, 0.0, 1024.0, 748.0);

                

                

                

        }

        else if (toInterfaceOrientation == UIInterfaceOrientationPortraitUpsideDown)

        {

                

                b=YES;

                self.view=mainvv;

                self.view.transform = CGAffineTransformIdentity;

                self.view.transform = CGAffineTransformMakeRotation(degreesToRadian(180));

                self.view.bounds = CGRectMake(0.0, 0.0, 768.0, 1004.0);

                

        }

        else if (toInterfaceOrientation == UIInterfaceOrientationLandscapeRight)

        {

                

                b=NO;

                self.view = self.vv;

                self.view.transform = CGAffineTransformIdentity;

                self.view.transform = CGAffineTransformMakeRotation(degreesToRadian(90));

                self.view.bounds = CGRectMake(0.0, 0.0, 1024.0, 748.0);

                

        }

        

        

}