Free-Thinker

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 UIKit
 
extension 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 UIKit
 
class 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()
    }
}

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