iOS 图片圆角加阴影 + 按钮的渐变颜色

转自：http://blog.csdn.net/qq_32052825/article/details/77503300?locationNum=5&fps=1

图片圆角加阴影

刚开始做项目时，给圆角加阴影，如： 
`UIImageView *image = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"leftbackiamge"]]; 
image.frame = CGRectMake(100, self.view.frame.size.height - 300, 100, 100); 
image.layer.masksToBounds = YES; 
image.layer.cornerRadius = 50; 
image.layer.shadowOffset = CGSizeMake(0, 5); 
image.layer.backgroundColor = [UIColor brownColor].CGColor; 
image.layer.shadowColor = [UIColor brownColor].CGColor; 
image.layer.shadowOpacity = 0.7; 
image.layer.cornerRadius = 50; 
[self.view addSubview:image]; 
这样写 但是出来的效果  
只有圆角没有阴影 
为何？ 
因为本身的masksToBounds方法就是超出父视图部分裁剪掉，所以加的阴影部分为超出部分，所以导致阴影显示不出来

解决方法：加一个图层，把圆角图片加到图层上

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UIImageView *image = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"leftbackiamge"]];
    image.frame = CGRectMake(100, self.view.frame.size.height - 300, 100, 100);
    //加个图层 设置阴影
    CALayer *layer = [[CALayer alloc] init];
    layer.frame = CGRectMake(100, self.view.frame.size.height - 300, 100, 100);
    layer.shadowOffset = CGSizeMake(0, 5);
    layer.backgroundColor = [UIColor brownColor].CGColor;
    layer.shadowColor = [UIColor brownColor].CGColor;
    layer.shadowOpacity = 0.7;
    layer.cornerRadius = 50;
    [self.view.layer addSublayer:layer];
    image.layer.masksToBounds = YES;
    image.layer.cornerRadius = 50;
    //注意一定要先上层再上image，这样保证image在层之上。
    [self.view addSubview:image];

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注意：必须先上层再加image，这样确保image在图层上 
效果： 
 
就成功了

下面说一下按钮的渐变颜色，一个道理把渐变的图层加到按钮图层上

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//渐变的按钮
    UIButton *lookBtn = [UIButton buttonWithType:(UIButtonTypeCustom)];
    lookBtn.frame = CGRectMake(100, 100,100, 100);
    [lookBtn setTitle:@"查看详情" forState:(UIControlStateNormal)];
    [lookBtn addTarget:self action:@selector(lookBtn) forControlEvents:(UIControlEventTouchUpInside)];
    lookBtn.layer.shadowColor=[TCUIColorFromRGB(0x24A7F2) colorWithAlphaComponent:0.5].CGColor;
    lookBtn.layer.shadowOffset=CGSizeMake(4, 4);
    lookBtn.layer.shadowOpacity=0.5;
    lookBtn.layer.shadowRadius= 5;

    //渐变颜色
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.colors = @[(__bridge id)TCUIColorFromRGB(0x5FCAFF).CGColor, (__bridge id)TCUIColorFromRGB(0x24A7F2).CGColor];
    gradientLayer.locations = @[@0.3, @1.0];
    gradientLayer.startPoint = CGPointMake(0, 0);
    gradientLayer.endPoint = CGPointMake(1.0, 0);
    gradientLayer.frame = CGRectMake(0, 0,  100, 100);
    gradientLayer.cornerRadius = 50;
    [lookBtn.layer addSublayer:gradientLayer];
    [self.view addSubview:lookBtn];

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建一个图层，保证渐变，加到按钮图层即可

此处为用到的宏定义 
#define TCUIColorFromRGB(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue &0xFF00) >>8))/255.0 blue:((float)(rgbValue &0xFF))/255.0 alpha:1.0]

效果如下 

代码demo地址：https://github.com/jinshuaier/shadow

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