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

[objc] view plaincopyprint?

1. #import "ViewController.h"
2. #import <QuartzCore/QuartzCore.h>
3. @interface ViewController ()
4. @property (nonatomic, weak) IBOutlet UIView *layerView1;
5. @property (nonatomic, weak) IBOutlet UIView *layerView2;
6. @end
7. @implementation ViewController
8. - (void)viewDidLoad
9. {
10. [super viewDidLoad];
11. //set the corner radius on our layers
12. self.layerView1.layer.cornerRadius = 20.0f;
13. self.layerView2.layer.cornerRadius = 20.0f;
14. //enable clipping on the second layer
15. self.layerView2.layer.masksToBounds = YES;
16. }
17. @end

稍微修改一下

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //set the corner radius on our layers
5. self.layerView1.layer.cornerRadius = 20.0f;
6. self.layerView2.layer.cornerRadius = 20.0f;
7. self.layerView1.clipsToBounds = YES;
8. //enable clipping on the second layer
9. self.layerView2.layer.masksToBounds = YES;
10. }

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

Layer Borders

例子4.2 borderWidth

[objc] view plaincopyprint?

1. @interface ViewController ()
2. @property (nonatomic, weak) IBOutlet UIView *layerView1;
3. @property (nonatomic, weak) IBOutlet UIView *layerView2;
4. @end
5. @implementation ViewController
6. - (void)viewDidLoad
7. {
8. [super viewDidLoad];
9. //set the corner radius on our layers
10. self.layerView1.layer.cornerRadius = 20.0f;
11. self.layerView2.layer.cornerRadius = 20.0f;
12. //add a border to our layers
13. self.layerView1.layer.borderWidth = 5.0f;
14. self.layerView2.layer.borderWidth = 5.0f;
15. //enable clipping on the second layer
16. self.layerView2.layer.masksToBounds = YES;
17. }
18. @end

修改代码 borderColor

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //set the corner radius on our layers
5. self.layerView1.layer.cornerRadius = 20.0f;
6. self.layerView2.layer.cornerRadius = 20.0f;
7. //add a border to our layers
8. self.layerView1.layer.borderWidth = 5.0f;
9. self.layerView1.layer.borderColor = [UIColor brownColor].CGColor;
10. self.layerView2.layer.borderWidth = 5.0f;
11. //enable clipping on the second layer
12. self.layerView2.layer.masksToBounds = YES;
13. }

再做个试验，修改代码

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //set the corner radius on our layers
5. //self.layerView1.layer.cornerRadius = 20.0f;
6. self.layerView2.layer.cornerRadius = 20.0f;
7. //add a border to our layers
8. self.layerView1.layer.borderWidth = 5.0f;
9. self.layerView1.layer.borderColor = [UIColor brownColor].CGColor;
10. self.layerView2.layer.borderWidth = 5.0f;
11. //enable clipping on the second layer
12. self.layerView2.layer.masksToBounds = YES;
13. }

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

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //load an image
5. UIImage *image = [UIImage imageNamed:@"Snowman.png"];
6. self.layerView.backgroundColor = [UIColor clearColor];
7. //add it directly to our view‘s layer
8. self.layerView.layer.contents = (__bridge id)image.CGImage;
9. //center the image
10. self.layerView.layer.contentsGravity = kCAGravityCenter;
11. //set the contentsScale to match screen
12. self.layerView.layer.contentsScale = image.scale;
13. self.layerView.layer.shadowOpacity = 0.3;
14. self.layerView.layer.shadowOffset = CGSizeMake(10, 20);
15. //clip the snowman to fit his bounds
16. //self.layerView.layer.masksToBounds = YES;
17. }

继续

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //load an image
5. UIImage *image = [UIImage imageNamed:@"Snowman.png"];
6. //self.layerView.backgroundColor = [UIColor clearColor];
7. //add it directly to our view‘s layer
8. self.layerView.layer.contents = (__bridge id)image.CGImage;
9. //center the image
10. self.layerView.layer.contentsGravity = kCAGravityCenter;
11. //set the contentsScale to match screen
12. self.layerView.layer.contentsScale = image.scale;
13. self.layerView.layer.shadowOpacity = 0.3;
14. self.layerView.layer.shadowOffset = CGSizeMake(10, 20);
15. //clip the snowman to fit his bounds
16. //self.layerView.layer.masksToBounds = YES;
17. }

再改

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //load an image
5. UIImage *image = [UIImage imageNamed:@"Snowman.png"];
6. self.layerView.backgroundColor = [UIColor clearColor];
7. //add it directly to our view‘s layer
8. self.layerView.layer.contents = (__bridge id)image.CGImage;
9. //center the image
10. self.layerView.layer.contentsGravity = kCAGravityCenter;
11. //set the contentsScale to match screen
12. self.layerView.layer.contentsScale = image.scale;
13. self.layerView.layer.shadowOpacity = 0.3;
14. self.layerView.layer.shadowOffset = CGSizeMake(10, 20);
15. //clip the snowman to fit his bounds
16. self.layerView.layer.masksToBounds = YES;
17. }

再改

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //load an image
5. UIImage *image = [UIImage imageNamed:@"Snowman.png"];
6. //self.layerView.backgroundColor = [UIColor clearColor];
7. //add it directly to our view‘s layer
8. self.layerView.layer.contents = (__bridge id)image.CGImage;
9. //center the image
10. self.layerView.layer.contentsGravity = kCAGravityCenter;
11. //set the contentsScale to match screen
12. self.layerView.layer.contentsScale = image.scale;
13. self.layerView.layer.shadowOpacity = 0.3;
14. self.layerView.layer.shadowOffset = CGSizeMake(10, 20);
15. //clip the snowman to fit his bounds
16. self.layerView.layer.masksToBounds = YES;
17. }

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

[objc] view plaincopyprint?

1. @interface ViewController ()
2. @property (nonatomic, weak) IBOutlet UIView *layerView1;
3. @property (nonatomic, weak) IBOutlet UIView *layerView2;
4. @end
5. @implementation ViewController
6. - (void)viewDidLoad
7. {
8. [super viewDidLoad];
9. //enable layer shadows
10. self.layerView1.layer.shadowOpacity = 0.5f;
11. self.layerView2.layer.shadowOpacity = 0.5f;
12. //create a square shadow
13. CGMutablePathRef squarePath = CGPathCreateMutable();
14. CGPathAddRect(squarePath, NULL, self.layerView1.bounds);
15. self.layerView1.layer.shadowPath = squarePath;
16. CGPathRelease(squarePath);
17. //create a circular shadow
18. CGMutablePathRef circlePath = CGPathCreateMutable();
19. CGPathAddEllipseInRect(circlePath, NULL, self.layerView2.bounds);
20. self.layerView2.layer.shadowPath = circlePath;
21. CGPathRelease(circlePath);
22. }

Layer Masking

例子4.5

[objc] view plaincopyprint?

1. @interface ViewController ()
2. @property (nonatomic, weak) IBOutlet UIImageView *imageView;
3. @end
4. @implementation ViewController
5. - (void)viewDidLoad
6. {
7. [super viewDidLoad];
8. //create mask layer
9. CALayer *maskLayer = [CALayer layer];
10. maskLayer.frame = self.imageView.bounds;
11. UIImage *maskImage = [UIImage imageNamed:@"Cone.png"];
12. maskLayer.contents = (__bridge id)maskImage.CGImage;
13. //apply mask to image layer
14. self.imageView.layer.mask = maskLayer;
15. }
16. @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   

[objc] view plaincopyprint?

1. @interface ViewController ()
2. @property (nonatomic, strong) IBOutletCollection(UIView) NSArray *digitViews;
3. @property (nonatomic, weak) NSTimer *timer;
4. @end
5. @implementation ViewController
6. - (void)viewDidLoad
7. {
8. [super viewDidLoad];
9. //get spritesheet image
10. UIImage *digits = [UIImage imageNamed:@"Digits.png"];
11. //set up digit views
12. for (UIView *view in self.digitViews)
13. {
14. //set contents
15. view.layer.contents = (__bridge  id)digits.CGImage;
16. view.layer.contentsRect = CGRectMake(0, 0, 0.1, 1.0);
17. view.layer.contentsGravity = kCAGravityResizeAspect;
18. //use nearest-neighbor scaling
19. view.layer.magnificationFilter = kCAFilterNearest;
20. }
21. //start timer
22. self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0
23. target:self
24. selector:@selector(tick)
25. userInfo:nil
26. repeats:YES];
27. //set initial clock time
28. [self tick];
29. }
30. - (void)setDigit:(NSInteger)digit forView:(UIView *)view
31. {
32. //adjust contentsRect to select correct digit
33. view.layer.contentsRect = CGRectMake(digit * 0.1, 0, 0.1, 1.0);
34. }
35. - (void)tick
36. {
37. //convert time to hours, minutes and seconds
38. NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
39. NSUInteger units = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
40. NSDateComponents *components = [calendar components:units fromDate:[NSDate date]];
41. //set hours
42. [self setDigit:components.hour / 10 forView:self.digitViews[0]];
43. [self setDigit:components.hour % 10 forView:self.digitViews[1]];
44. //set minutes
45. [self setDigit:components.minute / 10 forView:self.digitViews[2]];
46. [self setDigit:components.minute % 10 forView:self.digitViews[3]];
47. //set seconds
48. [self setDigit:components.second / 10 forView:self.digitViews[4]];
49. [self setDigit:components.second % 10 forView:self.digitViews[5]];
50. }
51. @end

kCAFilterNearest的效果

注释掉

[objc] view plaincopyprint?

1. //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：

[objc] view plaincopyprint?

1. @interface ViewController ()
2. @property (nonatomic, weak) IBOutlet UIView *containerView;
3. @end
4. @implementation ViewController
5. - (UIButton *)customButton
6. {
7. //create button
8. CGRect frame = CGRectMake(0, 0, 150, 50);
9. UIButton *button = [[UIButton alloc] initWithFrame:frame];
10. button.backgroundColor = [UIColor whiteColor];
11. button.layer.cornerRadius = 10;
12. //add label
13. frame = CGRectMake(20, 10, 110, 30);
14. UILabel *label = [[UILabel alloc] initWithFrame:frame];
15. label.text = @"Hello World";
16. //label.backgroundColor = [UIColor clearColor];
17. label.textAlignment = NSTextAlignmentCenter;
18. [button addSubview:label];
19. return button;
20. }
21. - (void)viewDidLoad
22. {
23. [super viewDidLoad];
24. //create opaque button
25. UIButton *button1 = [self customButton];
26. button1.center = CGPointMake(50, 150);
27. [self.containerView addSubview:button1];
28. //create translucent button
29. UIButton *button2 = [self customButton];
30. button2.center = CGPointMake(250, 150);
31. button2.alpha = 0.5;
32. [self.containerView addSubview:button2];
33. //enable rasterization for the translucent button
34. //button2.layer.shouldRasterize = YES;
35. //button2.layer.rasterizationScale = [UIScreen mainScreen].scale;
36. }
37. @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，

[objc] view plaincopyprint?

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. //create opaque button
5. UIButton *button1 = [self customButton];
6. button1.center = CGPointMake(50, 150);
7. [self.containerView addSubview:button1];
8. //create translucent button
9. UIButton *button2 = [self customButton];
10. button2.center = CGPointMake(250, 150);
11. button2.alpha = 0.5;
12. [self.containerView addSubview:button2];
13. //enable rasterization for the translucent button
14. button2.layer.shouldRasterize = YES;
15. button2.layer.rasterizationScale = [UIScreen mainScreen].scale;
16. }