IOS Core Animation Advanced Techniques的学习笔记(三)

第四章：Visual Effects

 

Rounded Corners

例子4.1 cornerRadius

源码在这里下载：http://www.informit.com/title/9780133440751

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *layerView1;
@property (nonatomic, weak) IBOutlet UIView *layerView2;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    //set the corner radius on our layers
    self.layerView1.layer.cornerRadius = 20.0f;
    self.layerView2.layer.cornerRadius = 20.0f;

    //enable clipping on the second layer
    self.layerView2.layer.masksToBounds = YES;
}

@end

稍微修改一下

- (void)viewDidLoad
{
    [super viewDidLoad];

    //set the corner radius on our layers
    self.layerView1.layer.cornerRadius = 20.0f;
    self.layerView2.layer.cornerRadius = 20.0f;

    self.layerView1.clipsToBounds = YES;

    //enable clipping on the second layer
    self.layerView2.layer.masksToBounds = YES;
}

前面讲过了，UIView的clipsToBounds的函数等同于masksToBounds


Layer Borders

例子4.2 borderWidth

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *layerView1;
@property (nonatomic, weak) IBOutlet UIView *layerView2;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    //set the corner radius on our layers
    self.layerView1.layer.cornerRadius = 20.0f;
    self.layerView2.layer.cornerRadius = 20.0f;

    //add a border to our layers
    self.layerView1.layer.borderWidth = 5.0f;
    self.layerView2.layer.borderWidth = 5.0f;

    //enable clipping on the second layer
    self.layerView2.layer.masksToBounds = YES;
}

@end

修改代码 borderColor

- (void)viewDidLoad
{
    [super viewDidLoad];

    //set the corner radius on our layers
    self.layerView1.layer.cornerRadius = 20.0f;
    self.layerView2.layer.cornerRadius = 20.0f;

    //add a border to our layers
    self.layerView1.layer.borderWidth = 5.0f;
    self.layerView1.layer.borderColor = [UIColor brownColor].CGColor;
    self.layerView2.layer.borderWidth = 5.0f;

    //enable clipping on the second layer
    self.layerView2.layer.masksToBounds = YES;
}

再做个试验，修改代码

- (void)viewDidLoad
{
    [super viewDidLoad];

    //set the corner radius on our layers
    //self.layerView1.layer.cornerRadius = 20.0f;
    self.layerView2.layer.cornerRadius = 20.0f;

    //add a border to our layers
    self.layerView1.layer.borderWidth = 5.0f;
    self.layerView1.layer.borderColor = [UIColor brownColor].CGColor;
    self.layerView2.layer.borderWidth = 5.0f;

    //enable clipping on the second layer
    self.layerView2.layer.masksToBounds = YES;
}

没有看到红色

再修改

看结果

验证borderWidth是往内部画的，和使用CGContextStrokeEllipseInRect画圆时的方式不同

Drop Shadows & Shadow Clipping

先修改例子2.2

- (void)viewDidLoad
{
    [super viewDidLoad];

    //load an image
    UIImage *image = [UIImage imageNamed:@"Snowman.png"];

    self.layerView.backgroundColor = [UIColor clearColor];

    //add it directly to our view's layer
    self.layerView.layer.contents = (__bridge id)image.CGImage;

    //center the image
    self.layerView.layer.contentsGravity = kCAGravityCenter;

    //set the contentsScale to match screen
    self.layerView.layer.contentsScale = image.scale;

    self.layerView.layer.shadowOpacity = 0.3;
    self.layerView.layer.shadowOffset = CGSizeMake(10, 20);

    //clip the snowman to fit his bounds
    //self.layerView.layer.masksToBounds = YES;
}

继续

- (void)viewDidLoad
{
    [super viewDidLoad];

    //load an image
    UIImage *image = [UIImage imageNamed:@"Snowman.png"];

    //self.layerView.backgroundColor = [UIColor clearColor];

    //add it directly to our view's layer
    self.layerView.layer.contents = (__bridge id)image.CGImage;

    //center the image
    self.layerView.layer.contentsGravity = kCAGravityCenter;

    //set the contentsScale to match screen
    self.layerView.layer.contentsScale = image.scale;

    self.layerView.layer.shadowOpacity = 0.3;
    self.layerView.layer.shadowOffset = CGSizeMake(10, 20);

    //clip the snowman to fit his bounds
    //self.layerView.layer.masksToBounds = YES;
}

再改

- (void)viewDidLoad
{
    [super viewDidLoad];

    //load an image
    UIImage *image = [UIImage imageNamed:@"Snowman.png"];

    self.layerView.backgroundColor = [UIColor clearColor];

    //add it directly to our view's layer
    self.layerView.layer.contents = (__bridge id)image.CGImage;

    //center the image
    self.layerView.layer.contentsGravity = kCAGravityCenter;

    //set the contentsScale to match screen
    self.layerView.layer.contentsScale = image.scale;

    self.layerView.layer.shadowOpacity = 0.3;
    self.layerView.layer.shadowOffset = CGSizeMake(10, 20);

    //clip the snowman to fit his bounds
    self.layerView.layer.masksToBounds = YES;
}

再改

- (void)viewDidLoad
{
    [super viewDidLoad];

    //load an image
    UIImage *image = [UIImage imageNamed:@"Snowman.png"];

    //self.layerView.backgroundColor = [UIColor clearColor];

    //add it directly to our view's layer
    self.layerView.layer.contents = (__bridge id)image.CGImage;

    //center the image
    self.layerView.layer.contentsGravity = kCAGravityCenter;

    //set the contentsScale to match screen
    self.layerView.layer.contentsScale = image.scale;

    self.layerView.layer.shadowOpacity = 0.3;
    self.layerView.layer.shadowOffset = CGSizeMake(10, 20);

    //clip the snowman to fit his bounds
    self.layerView.layer.masksToBounds = YES;
}

shadow是根据layer实际显示的内容绘制的

再看看例子4.3去体会一下

源码在这里下载：http://www.informit.com/title/9780133440751

 

The shadowPath Property

例子4.4

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *layerView1;
@property (nonatomic, weak) IBOutlet UIView *layerView2;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    //enable layer shadows
    self.layerView1.layer.shadowOpacity = 0.5f;
    self.layerView2.layer.shadowOpacity = 0.5f;

    //create a square shadow
    CGMutablePathRef squarePath = CGPathCreateMutable();
    CGPathAddRect(squarePath, NULL, self.layerView1.bounds);
    self.layerView1.layer.shadowPath = squarePath;
    CGPathRelease(squarePath);

    //create a circular shadow
    CGMutablePathRef circlePath = CGPathCreateMutable();
    CGPathAddEllipseInRect(circlePath, NULL, self.layerView2.bounds);
    self.layerView2.layer.shadowPath = circlePath;
    CGPathRelease(circlePath);
}

 

Layer Masking

例子4.5

 

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIImageView *imageView;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    //create mask layer
    CALayer *maskLayer = [CALayer layer];
    maskLayer.frame = self.imageView.bounds;
    UIImage *maskImage = [UIImage imageNamed:@"Cone.png"];
    maskLayer.contents = (__bridge id)maskImage.CGImage;

    //apply mask to image layer
    self.imageView.layer.mask = maskLayer;
}

@end

Scaling Filters

minificationFilter和magnificationFilter属性

这两个属性主要是设置layer的‘contents’数据缩放拉伸时的描绘方式，minificationFilter用于缩小，magnificationFilter用于放大

默认值都是kCAFilterLinear即‘linear’

有3中设置：kCAFilterLinear，kCAFilterNearest，kCAFilterTrilinear

kCAFilterLinear：默认值，缩放平滑，但容易产生模糊效果

kCAFilterTrilinear：基本和kCAFilterLinear相同

kCAFilterNearest：速度快不会产生模糊，但会降低质量并像素化图像

例子4.6，放大图像，设置magnificationFilter

原图   

@interface ViewController ()

@property (nonatomic, strong) IBOutletCollection(UIView) NSArray *digitViews;
@property (nonatomic, weak) NSTimer *timer;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    //get spritesheet image
    UIImage *digits = [UIImage imageNamed:@"Digits.png"];

    //set up digit views
    for (UIView *view in self.digitViews)
    {
        //set contents
        view.layer.contents = (__bridge  id)digits.CGImage;
        view.layer.contentsRect = CGRectMake(0, 0, 0.1, 1.0);
        view.layer.contentsGravity = kCAGravityResizeAspect;

        //use nearest-neighbor scaling
        view.layer.magnificationFilter = kCAFilterNearest;
    }

    //start timer
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0
                                                  target:self
                                                selector:@selector(tick)
                                                userInfo:nil
                                                 repeats:YES];
    //set initial clock time
    [self tick];
}

- (void)setDigit:(NSInteger)digit forView:(UIView *)view
{
    //adjust contentsRect to select correct digit
    view.layer.contentsRect = CGRectMake(digit * 0.1, 0, 0.1, 1.0);
}

- (void)tick
{
    //convert time to hours, minutes and seconds
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSUInteger units = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
    NSDateComponents *components = [calendar components:units fromDate:[NSDate date]];

    //set hours
    [self setDigit:components.hour / 10 forView:self.digitViews[0]];
    [self setDigit:components.hour % 10 forView:self.digitViews[1]];

    //set minutes
    [self setDigit:components.minute / 10 forView:self.digitViews[2]];
    [self setDigit:components.minute % 10 forView:self.digitViews[3]];

    //set seconds
    [self setDigit:components.second / 10 forView:self.digitViews[4]];
    [self setDigit:components.second % 10 forView:self.digitViews[5]];
}

@end

kCAFilterNearest的效果

注释掉

//view.layer.magnificationFilter = kCAFilterNearest;

使用用默认kCAFilterLinear效果

明显模糊了

Group Opacity

先看例子4.7：

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *containerView;

@end

@implementation ViewController

- (UIButton *)customButton
{
    //create button
    CGRect frame = CGRectMake(0, 0, 150, 50);
    UIButton *button = [[UIButton alloc] initWithFrame:frame];
    button.backgroundColor = [UIColor whiteColor];
    button.layer.cornerRadius = 10;

    //add label
    frame = CGRectMake(20, 10, 110, 30);
    UILabel *label = [[UILabel alloc] initWithFrame:frame];
    label.text = @"Hello World";
    //label.backgroundColor = [UIColor clearColor];
    label.textAlignment = NSTextAlignmentCenter;
    [button addSubview:label];

    return button;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    //create opaque button
    UIButton *button1 = [self customButton];
    button1.center = CGPointMake(50, 150);
    [self.containerView addSubview:button1];

    //create translucent button
    UIButton *button2 = [self customButton];
    button2.center = CGPointMake(250, 150);
    button2.alpha = 0.5;
    [self.containerView addSubview:button2];

    //enable rasterization for the translucent button
    //button2.layer.shouldRasterize = YES;
    //button2.layer.rasterizationScale = [UIScreen mainScreen].scale;
}

@end

button的背景和其subView label的背景同为白色，

左边的button是不透明的，右边用同样方式创建的button透明度为50%，发现右边的label透明度不同于button

其实很容易发现原因，将button透明度设为50%后，button显示50%自己的颜色和其后面50%的颜色，label在

button上面，label也是50%显示择机的颜色，但后面有已经50%透明的button，还要再显示它的50%，即原

button的25%，重合后为75%，即出现上图效果。

有两种解决方法：

1.在工程的Info.plist文件中，添加UIViewGroupOpacity并设为YES

2.设置layer属性shouldRasterize，设为YES可在设置opacity属性时将layer及其sublayer叠加为一张图像

修改代码，

- (void)viewDidLoad
{
    [super viewDidLoad];

    //create opaque button
    UIButton *button1 = [self customButton];
    button1.center = CGPointMake(50, 150);
    [self.containerView addSubview:button1];

    //create translucent button
    UIButton *button2 = [self customButton];
    button2.center = CGPointMake(250, 150);
    button2.alpha = 0.5;
    [self.containerView addSubview:button2];

    //enable rasterization for the translucent button
    button2.layer.shouldRasterize = YES;
    button2.layer.rasterizationScale = [UIScreen mainScreen].scale;
}