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