iOS - 图片添加水印

春夏秋冬
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.frame];
    imageView.backgroundColor = [UIColor yellowColor];
    [self.view addSubview:imageView];
    
    
    /**
     *   UIGraphicsBeginImageContextWithOptions(<#CGSize size#>, <#BOOL opaque#>, <#CGFloat scale#>)
     *
     *   <#CGSize size#> : 位图的尺寸大小,这里大小设置为图片的尺寸大小
     *   <#BOOL opaque#> : opaque 为不透明度 , NO 为透明
     *   <#CGFloat scale#> : scale 缩放 取值为 0 ,表示不缩放
     *
     */
    
    UIImage *BGimage = [UIImage imageNamed:@"20141216155246_eifSM.jpg"];
   
    // 1、开启位图上下文,由于位图上下文跟 View 没有关系,所以不需要在 drawRect 中
    
    UIGraphicsBeginImageContextWithOptions(BGimage.size, NO, 0);
    
    // 2、绘制原生图片
    [BGimage drawAtPoint:CGPointZero];
    
    // 3、给原生图片添加文字
    
    NSMutableDictionary *dic = [NSMutableDictionary dictionary];
    dic[NSForegroundColorAttributeName] = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0];
    dic[NSFontAttributeName] = [UIFont systemFontOfSize:90];
    
    
    NSString *str = @"@春夏秋冬";
    [str drawAtPoint:CGPointMake(600, 2500) withAttributes:dic];
    
    
    // 4、生成一张图片,从上下文中获取当前的图片
    
    UIImage *imageWater = UIGraphicsGetImageFromCurrentImageContext();
    
    imageView.image = imageWater;
    
    // 关闭图形上下文
    UIGraphicsEndImageContext();
    
    
}

@来源 小码哥 视频, 感谢小码哥!

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