iOS-给图片添加水印效果的方法并保存图片到指定路径

这里介绍两种方法：

方法一：添加文字水印，这里说的文字水印是指将开发者定义的文字直接添加到图片上，代码如下:

UIImage *img = [UIImage imageNamed:@"3G_alert.png"];  //需要加水印的图片
    CGSize size = self.view.frame.size; //设置上下文（画布）大小
    UIGraphicsBeginImageContext(size); //创建一个基于位图的上下文(context)，并将其设置为当前上下文
    CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取当前上下文
    NSString *title = @"舵手网络";  //需要添加的水印文字
    CGContextTranslateCTM(contextRef, 0, self.view.bounds.size.height);  //画布的高度
    CGContextScaleCTM(contextRef, 1.0, -1.0);  //画布翻转
    CGContextDrawImage(contextRef, self.view.frame, [img CGImage]);  //在上下文种画当前图片
 
    [[UIColor redColor] set];  //上下文种的文字属性
    CGContextTranslateCTM(contextRef, 0, self.view.bounds.size.height);
    CGContextScaleCTM(contextRef, 1.0, -1.0);
    UIFont *font = [UIFont boldSystemFontOfSize:40];
    [title drawInRect:CGRectMake(100, 400, 200, 80) withFont:font];
    UIImage *res =UIGraphicsGetImageFromCurrentImageContext();  //从当前上下文种获取图片
    UIGraphicsEndImageContext(); //移除栈顶的基于当前位图的图形上下文。
    NSArray *savePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *p = [savePath objectAtIndex:0];
    NSLog(@"%@",p);
    NSString *dataFilePath = [p stringByAppendingPathComponent:@"1.png"];
 
    NSData *imageData = UIImagePNGRepresentation(res);
    [imageData writeToFile:dataFilePath atomically:YES];
 
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
    [imageView setImage:res];
    [self.view addSubview:imageView];

 方法二：添加图片水印，顾名思义，就是两张图片，一张原图，一张水印图片，代码如下：

 UIImage *img = [UIImage imageNamed:@"demo.jpg"];  //需要加水印的图片
    UIImage *smallImg = [UIImage imageNamed:@"water.png"];
    CGSize size = self.view.frame.size; //设置上下文（画布）大小
    UIGraphicsBeginImageContext(size); //创建一个基于位图的上下文(context)，并将其设置为当前上下文
    CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取当前上下文
    CGContextTranslateCTM(contextRef, 0, self.view.bounds.size.height);  //画布的高度
    CGContextScaleCTM(contextRef, 1.0, -1.0);  //画布翻转
 
    CGContextDrawImage(contextRef, self.view.frame, [img CGImage]);  //在上下文种画当前图片
    CGContextDrawImage(contextRef, CGRectMake(100, 50, 200, 80), [smallImg CGImage]);
    UIImage *res = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext(); //移除栈顶的基于当前位图的图形上下文。
    NSArray *savePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *p = [savePath objectAtIndex:0];
    NSLog(@"%@",p);
    NSString *dataFilePath = [p stringByAppendingPathComponent:@"1.png"];
 
    NSData *imageData = UIImageJPEGRepresentation(res, 1.0);
    [imageData writeToFile:dataFilePath atomically:YES];
 
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
    [imageView setImage:res];
    [self.view addSubview:imageView];