IOS图片上添加水印文字（微博上图片上得水印文字）

建一个类目（不知道怎么建的可以去百度一下） UIImage的类目

类目的.h文件  文件名为UIImage+watermark

#import <UIKit/UIKit.h>

@interface UIImage (watermark)

//定义一个方法

- (UIImage *)watermarkImage:(NSString *)text;

@end

.m文件的实现

#import "UIImage+watermark.h"

@implementation UIImage (watermark)

- (UIImage *)watermarkImage:(NSString *)text{

//1.获取上下文

UIGraphicsBeginImageContext(self.size);

//2.绘制图片

[self
drawInRect:CGRectMake(0,
0, self.size.width,
self.size.height)];

//3.绘制水印文字

CGRect rect = CGRectMake(0,
self.size.height-20,
self.size.width,
20);

NSMutableParagraphStyle *style = [[NSMutableParagraphStyle
defaultParagraphStyle]
mutableCopy];

style.alignment =
NSTextAlignmentCenter;

//文字的属性

NSDictionary *dic =
@{

NSFontAttributeName:[UIFont
systemFontOfSize:13],

NSParagraphStyleAttributeName:style,

NSForegroundColorAttributeName:[UIColor
whiteColor]

};

//将文字绘制上去

[text drawInRect:rect
withAttributes:dic];

//4.获取绘制到得图片

UIImage *watermarkImage =
UIGraphicsGetImageFromCurrentImageContext();

//5.结束图片的绘制

UIGraphicsEndImageContext();

return watermarkImage;

}

@end

然后再viewController 的视图上添加一个UIImageView 导入类目（UIImage+watermark）文件

#import "ViewController.h"

#import "UIImage+watermark.h"

@interface
ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

[super
viewDidLoad];

UIImage *image = [UIImage
imageNamed:@"baymax.jpg"];

//调用类目的方法实现功能

UIImage *img = [image
watermarkImage:@"@大白"];

UIImageView *imageView = [[UIImageView
alloc] initWithImage:img];

//    imageView.frame = self.view.bounds;

[self.view
addSubview:imageView];

}

- (void)didReceiveMemoryWarning {

[super
didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end