想要给图片添加文字水印或者注释，我们需要实现在UIImage上写字的功能。
1，效果图如下：
（在图片左上角和右下角都添加了文字。）
2，为方便使用，我们通过扩展UIImage类来实现添加水印功能
（文字大小，文字颜色，背景色，位置，边距都可以设置）
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//--- UIImageExtension.swift ---import UIKitextension UIImage{ //水印位置枚举 enum WaterMarkCorner{ case TopLeft case TopRight case BottomLeft case BottomRight } //添加水印方法 func waterMarkedImage(waterMarkText:String, corner:WaterMarkCorner = .BottomRight, margin:CGPoint = CGPoint(x: 20, y: 20), waterMarkTextColor:UIColor = UIColor.whiteColor(), waterMarkTextFont:UIFont = UIFont.systemFontOfSize(20), backgroundColor:UIColor = UIColor.clearColor()) -> UIImage{ let textAttributes = [NSForegroundColorAttributeName:waterMarkTextColor, NSFontAttributeName:waterMarkTextFont] let textSize = NSString(string: waterMarkText).sizeWithAttributes(textAttributes) var textFrame = CGRectMake(0, 0, textSize.width, textSize.height) let imageSize = self.size switch corner{ case .TopLeft: textFrame.origin = margin case .TopRight: textFrame.origin = CGPoint(x: imageSize.width - textSize.width - margin.x, y: margin.y) case .BottomLeft: textFrame.origin = CGPoint(x: margin.x, y: imageSize.height - textSize.height - margin.y) case .BottomRight: textFrame.origin = CGPoint(x: imageSize.width - textSize.width - margin.x, y: imageSize.height - textSize.height - margin.y) } // 开始给图片添加文字水印 UIGraphicsBeginImageContext(imageSize) self.drawInRect(CGRectMake(0, 0, imageSize.width, imageSize.height)) NSString(string: waterMarkText).drawInRect(textFrame, withAttributes: textAttributes) let waterMarkedImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return waterMarkedImage }} |
3，使用样例
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import UIKitclass ViewController: UIViewController { @IBOutlet weak var imageView: UIImageView! override func viewDidLoad() { super.viewDidLoad() //使用链式调用方法，给图片添加两条水印 imageView.image = UIImage(named:"bg")? .waterMarkedImage("做最好的开发者知识平台") .waterMarkedImage("hangge.com", corner: .TopLeft, margin: CGPoint(x: 20, y: 20), waterMarkTextColor: UIColor.blackColor(), waterMarkTextFont: UIFont.systemFontOfSize(45), backgroundColor: UIColor.clearColor()) } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() }} |
