Swift - 给图片添加图片水印（图片上绘制另一张图，并可设透明度）

我前面写了篇文章讲解如何给图片添加文字水印，而如果想要添加图片类型的水印也很简单，只要把原来代码里添加文字的部分改成图片即可。

1，效果图如下：

（在图片左上角添加了一个半透明的logo图片）

2，为方便使用，我们通过扩展UIImage类来实现添加图片水印功能

（水印图片透明度，位置，边距都可以设置）

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//--- UIImageExtension.swift --- extension UIImage{           //水印位置枚举     enum WaterMarkCorner{         case TopLeft         case TopRight         case BottomLeft         case BottomRight     }           //添加图片水印方法     func waterMarkedImage(waterMarkImage:UIImage, corner:WaterMarkCorner = .BottomRight,         margin:CGPoint = CGPoint(x: 20, y: 20), alpha:CGFloat = 1) -> UIImage{                           var markFrame = CGRectMake(0, 0, waterMarkImage.size.width, waterMarkImage.size.height)             let imageSize = self.size                           switch corner{             case .TopLeft:                 markFrame.origin = margin             case .TopRight:                 markFrame.origin = CGPoint(x: imageSize.width - waterMarkImage.size.width - margin.x,                     y: margin.y)             case .BottomLeft:                 markFrame.origin = CGPoint(x: margin.x,                     y: imageSize.height - waterMarkImage.size.height - margin.y)             case .BottomRight:                 markFrame.origin = CGPoint(x: imageSize.width - waterMarkImage.size.width - margin.x,                     y: imageSize.height - waterMarkImage.size.height - margin.y)             }                           // 开始给图片添加图片             UIGraphicsBeginImageContext(imageSize)             self.drawInRect(CGRectMake(0, 0, imageSize.width, imageSize.height))             waterMarkImage.drawInRect(markFrame, blendMode: .Normal, alpha: alpha)             let waterMarkedImage = UIGraphicsGetImageFromCurrentImageContext()             UIGraphicsEndImageContext()                           return waterMarkedImage     } }

3，使用样例

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import UIKit   class ViewController: UIViewController {       @IBOutlet weak var imageView: UIImageView!           override func viewDidLoad() {         super.viewDidLoad()                          //给图片添加水印         imageView.image = UIImage(named:"bg")?             .waterMarkedImage(UIImage(named: "logo7")!,corner: .TopLeft,                 margin: CGPoint(x: 20, y: 20), alpha:1)     }       override func didReceiveMemoryWarning() {         super.didReceiveMemoryWarning()     } }