將字符串添加到圖形上下文的方法
- (void)drawAtPoint:(CGPoint)point withAttributes:(nullable NSDictionary<NSAttributedStringKey, id> *)attrs
- (void)drawInRect:(CGRect)rect withAttributes:(nullable NSDictionary<NSAttributedStringKey, id> *)attrs
將字符串添加到圖形上下文的方法
- (void)drawAtPoint:(CGPoint)point;              
 
// mode = kCGBlendModeNormal, alpha = 1.0
- (void)drawAtPoint:(CGPoint)point blendMode:(CGBlendMode)blendMode alpha:(CGFloat)alpha;
 
- (void)drawInRect:(CGRect)rect;               
 
// mode = kCGBlendModeNormal, alpha = 1.0
- (void)drawInRect:(CGRect)rect blendMode:(CGBlendMode)blendMode alpha:(CGFloat)alpha;

//1. 要手動創(chuàng)建一個位圖上下文,創(chuàng)建位圖上下文時，要指定大小,指定的大小，決定著生成圖片的尺寸是多大
void UIGraphicsBeginImageContext(CGSize size);
 
//2. 把內容繪制到上下文當中
//2.1繪制原始圖片
//2.2繪制文字
//2.3繪制logo
 
//3. 從上下文當中生成一張圖片，把上下文當中繪制的所有內容合成在一起生成一張跟上下文尺度一樣的圖片
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext() ;
 
//4.手動創(chuàng)建的上下文一定要手動去銷毀掉
UIGraphicsEndImageContext() ;

#import <UIKit/UIKit.h>
 
NS_ASSUME_NONNULL_BEGIN
 
@interface SWWaterMarkImage : UIImage
-(UIImage *)WaterImageWithImage:(UIImage *)image ImageLogo:(UIImage *)imageLogo title:(NSString *)string ;
+(UIImage *)WaterImageWithImage:(UIImage *)image ImageLogo:(UIImage *)imageLogo title:(NSString *)string ;
@end
 
NS_ASSUME_NONNULL_END

@implementation SWWaterMarkImage
-(UIImage *)WaterImageWithImage:(UIImage *)image ImageLogo:(UIImage *)imageLogo title:(NSString *)string {
  
 //1.要手動創(chuàng)建一個位圖上下文
 UIGraphicsBeginImageContext(image.size) ;
  
 //2.繪制到內容上下文中
 //原始圖片渲染
 [image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
  
 //文字
 NSDictionary *attributeDict = @{
         NSFontAttributeName : [UIFont systemFontOfSize:20.f],
         NSForegroundColorAttributeName:[UIColor whiteColor],
//         NSBackgroundColorAttributeName :[UIColor redColor]
         } ;
 CGRect rectSize = [string boundingRectWithSize:CGSizeMake(MAXFLOAT, 30) options:NSStringDrawingUsesDeviceMetrics attributes:attributeDict context:nil] ;
 CGFloat x = image.size.width - rectSize.size.width - 10 ;
 CGFloat y = image.size.height - 30 ;
 [string drawAtPoint:CGPointMake(x, y) withAttributes:attributeDict] ;
  
 //logo圖片
 CGFloat waterW = 30;
 CGFloat waterH = 30;
 CGFloat waterX = x - waterW - 10 ;
 CGFloat waterY = y - 3 ;
 [imageLogo drawInRect:CGRectMake(waterX, waterY, waterW, waterH)] ;
 
 //3.從當前的上下文當中生成一張新的圖片
 UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext() ;
  
 //4.手動創(chuàng)建的上下文一定要手動去銷毀掉
 UIGraphicsEndImageContext() ;
  
 return newImage ;
}
 
+(UIImage *)WaterImageWithImage:(UIImage *)image ImageLogo:(UIImage *)imageLogo title:(NSString *)string {
 return [[self alloc]WaterImageWithImage:image ImageLogo:imageLogo title:string] ;
}
@end

#import "ViewController.h"
#import "SWWaterMarkImage.h"
@interface ViewController ()
@property(nonatomic,strong)UIImageView *imageView ;
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
 [super viewDidLoad];
  
 //生成一張加水印圖片步驟：
 /*
  可以在任何方法中生成圖片,不一定在drawRect:方法中生成
  1.要手動創(chuàng)建一個位圖上下文,創(chuàng)建位圖上下文時，要指定大小,指定的大小，決定著生成圖片的尺寸是多大
  2.把內容繪制到上下文當中
  3.從上下文當中生成一張圖片，把上下文當中繪制的所有內容合成在一起生成一張跟上下文尺度一樣的圖片
  4.手動創(chuàng)建的上下文一定要手動去銷毀掉
  */
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
 UIImage *newImage = [SWWaterMarkImage WaterImageWithImage:[UIImage imageNamed:@"18d8bc3eb13533fa65021ddba5d3fd1f40345b8b"] ImageLogo:[UIImage imageNamed:@"logo"] title:@"蕪湖亞原子網(wǎng)絡科技有限公司"] ;
 //5.將生成的image顯示到imageView上去
 self.imageView = [[UIImageView alloc]init] ;
 self.imageView.frame = CGRectMake(0, 100, 375, 250) ;
 self.imageView.image = newImage ;
 [self.view addSubview:self.imageView] ;
}
 
 
 
@end