建一個類目（不知道怎麼建的可以去百度一下） UIImage的類目

類目的.h文件 文件名為UIImage+watermark

 

#import

 

@interface UIImage (watermark)

//定義一個方法

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

@end

.m文件的實現

 

#import "UIImage+watermark.h"

 

@implementation UIImage (watermark)

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

 

//1.獲取上下文

UIGraphicsBeginImageContext(self.size);

 

//2.繪制圖片

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

 

//3.繪制水印文字

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

 

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

style.alignment = NSTextAlignmentCenter;

//文字的屬性

NSDictionary *dic = @{

NSFontAttributeName:[UIFont systemFontOfSize:13],

NSParagraphStyleAttributeName:style,

NSForegroundColorAttributeName:[UIColor whiteColor]

};

//將文字繪制上去

[text drawInRect:rect withAttributes:dic];

 

//4.獲取繪制到得圖片

UIImage *watermarkImage = UIGraphicsGetImageFromCurrentImageContext();

 

//5.結束圖片的繪制

UIGraphicsEndImageContext();

 

return watermarkImage;

}

@end

然後再viewController 的視圖上添加一個UIImageView 導入類目（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"];

 

//調用類目的方法實現功能

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