iOS 不规则的ImageView「建议收藏」

我们在做iOS开发的时候，往往须要实现不规则形状的头像，如：

那怎样去实现？

通常图片都是矩形的，假设想在client去实现不规则的头像，须要自己去实现。

1.使用layer去实现, 见http://blog.csdn.net/johnzhjfly/article/details/39993345

2.使用CAShapeLayer, CALayer怎样去实现

我们来看看怎样使用CAShapeLayer去实现,

定义一个ShapedImageView。继承于UIView， 代码例如以下：

#import "ShapedImageView.h"

@interface ShapedImageView()
{
    CALayer      *_contentLayer;
    CAShapeLayer *_maskLayer;
}
@end

@implementation ShapedImageView

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self setup];
    }
    return self;
}

- (void)setup
{
    _maskLayer = [CAShapeLayer layer];
    _maskLayer.path = [UIBezierPath bezierPathWithOvalInRect:self.bounds].CGPath;
    _maskLayer.fillColor = [UIColor blackColor].CGColor;
    _maskLayer.strokeColor = [UIColor redColor].CGColor;
    _maskLayer.frame = self.bounds;
    _maskLayer.contentsCenter = CGRectMake(0.5, 0.5, 0.1, 0.1);
    _maskLayer.contentsScale = [UIScreen mainScreen].scale;
    
    _contentLayer = [CALayer layer];
    _contentLayer.mask = _maskLayer;
    _contentLayer.frame = self.bounds;
    [self.layer addSublayer:_contentLayer];
    
}

- (void)setImage:(UIImage *)image
{
    _contentLayer.contents = (id)image.CGImage;
}

@end

声明了用于maskLayer个CAShapedLayer。 CAShapedLayer有个path的属性。将内容Layer的mask设置为maskLayer, 就能够获取到我们想要的形状。

path我们能够使用CAMutablePath随意的构造，上述的代码执行想过例如以下：

假设将代码改成

    _maskLayer = [CAShapeLayer layer];
    _maskLayer.path = [UIBezierPath bezierPathWithRoundedRect:self.bounds cornerRadius:20].CGPath;
    _maskLayer.fillColor = [UIColor blackColor].CGColor;
    _maskLayer.strokeColor = [UIColor redColor].CGColor;
    _maskLayer.frame = self.bounds;
    _maskLayer.contentsCenter = CGRectMake(0.5, 0.5, 0.1, 0.1);
    _maskLayer.contentsScale = [UIScreen mainScreen].scale;                 //很关键设置自己主动拉伸的效果且不变形
    
    _contentLayer = [CALayer layer];
    _contentLayer.mask = _maskLayer;
    _contentLayer.frame = self.bounds;
    [self.layer addSublayer:_contentLayer];

的效果:

假设将代码改成:

    CGMutablePathRef path = CGPathCreateMutable();
    CGPoint origin = self.bounds.origin;
    CGFloat radius = CGRectGetWidth(self.bounds) / 2;
    CGPathMoveToPoint(path, NULL, origin.x, origin.y + 2 *radius);
    CGPathMoveToPoint(path, NULL, origin.x, origin.y + radius);
    
    CGPathAddArcToPoint(path, NULL, origin.x, origin.y, origin.x + radius, origin.y, radius);
    CGPathAddArcToPoint(path, NULL, origin.x + 2 * radius, origin.y, origin.x + 2 * radius, origin.y + radius, radius);
    CGPathAddArcToPoint(path, NULL, origin.x + 2 * radius, origin.y + 2 * radius, origin.x + radius, origin.y + 2  * radius, radius);
    CGPathAddLineToPoint(path, NULL, origin.x, origin.y + 2 * radius);
    
    _maskLayer = [CAShapeLayer layer];
    _maskLayer.path = path;
    _maskLayer.fillColor = [UIColor blackColor].CGColor;
    _maskLayer.strokeColor = [UIColor clearColor].CGColor;
    _maskLayer.frame = self.bounds;
    _maskLayer.contentsCenter = CGRectMake(0.5, 0.5, 0.1, 0.1);
    _maskLayer.contentsScale = [UIScreen mainScreen].scale;                 //很关键设置自己主动拉伸的效果且不变形
    
    _contentLayer = [CALayer layer];
    _contentLayer.mask = _maskLayer;
    _contentLayer.frame = self.bounds;
    [self.layer addSublayer:_contentLayer];

将是这个效果:

理论上我们能够构造出随意想要的形状。可是有些形状假设你不熟悉几何知识的话是构造不出正确的

path的，从代码上我们能够看到我们能够通过设置CALayer的contents属性来设置显示的内容，那我们

是不是能够通过设置CAShapedLayer的contents来设置maskLayer呢？答案是肯定的，代码例如以下：

    _maskLayer = [CAShapeLayer layer];
    _maskLayer.fillColor = [UIColor blackColor].CGColor;
    _maskLayer.strokeColor = [UIColor clearColor].CGColor;
    _maskLayer.frame = self.bounds;
    _maskLayer.contentsCenter = CGRectMake(0.5, 0.5, 0.1, 0.1);
    _maskLayer.contentsScale = [UIScreen mainScreen].scale;                 //很关键设置自己主动拉伸的效果且不变形
    _maskLayer.contents = (id)[UIImage imageNamed:@"gray_bubble_right@2x.png"].CGImage;
    
    _contentLayer = [CALayer layer];
    _contentLayer.mask = _maskLayer;
    _contentLayer.frame = self.bounds;
    [self.layer addSublayer:_contentLayer];

gray_bubble_right就是你想要的形状，执行效果例如以下:

不停的改变CALayer的一个坏处就是很的损耗性能，假设你有一个cell的列表。每一个列表有个头像的话。高速滑动的时候。你会发现很的卡。

此时理想的解决方式是使用CGPath或者UIBezierPath构建不规则的path，然后clip画出来。这里就不具体解说了。

演示样例代码例如以下:

- (UIImage *)maskImage
{
    // start with an image
    UIImage * fooImage = self;//[UIImage imageNamed:@"foo.png"];
    CGRect imageRect = CGRectMake(0, 0, fooImage.size.width, fooImage.size.height);
    // set the implicit graphics context ("canvas") to a bitmap context for images
    UIGraphicsBeginImageContextWithOptions(imageRect.size, NO, 0.0);
    // create a bezier path defining rounded corners
    UIBezierPath * path = [UIBezierPath bezierPathWithRect:imageRect];
    CGFloat radius = fooImage.size.width / 2.5;
    CGFloat _radius = radius;
    //construct your shaped path
    [path moveToPoint:CGPointMake(0, 0)];
    [path addArcWithCenter:CGPointMake(radius, radius) radius:_radius startAngle:M_PI endAngle:3 * M_PI / 2 clockwise:TRUE];
    [path moveToPoint:CGPointMake(fooImage.size.width, 0)];
    [path addArcWithCenter:CGPointMake(fooImage.size.width - radius, radius) radius:_radius startAngle:3 * M_PI / 2 endAngle:2 * M_PI clockwise:TRUE];
    [path moveToPoint:CGPointMake(fooImage.size.width, fooImage.size.height)];
    [path addArcWithCenter:CGPointMake(fooImage.size.width - radius, fooImage.size.height - radius) radius:_radius startAngle:0 endAngle:M_PI / 2 clockwise:TRUE];
    [path moveToPoint:CGPointMake(0, fooImage.size.height)];
    [path addArcWithCenter:CGPointMake(radius, fooImage.size.height - radius) radius:_radius startAngle:M_PI / 2 endAngle:M_PI clockwise:TRUE];
    path.flatness = 1000;
    path.lineCapStyle = kCGLineCapRound;
    path.lineJoinStyle = kCGLineJoinRound;
    // use this path for clipping in the implicit context
    [path addClip];
    // draw the image into the implicit context
    [fooImage drawInRect:imageRect];
    // save the clipped image from the implicit context into an image
    UIImage *maskedImage = UIGraphicsGetImageFromCurrentImageContext();
    // cleanup
    UIGraphicsEndImageContext();
    return maskedImage;
}

源码