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()
}
} |