图片上添加文字并合成

//添加文字水印到指定图片上
-(UIImage *)addWaterText:(NSString *)text Attributes:(NSDictionary*)atts toImage:(UIImage *)img rect:(CGRect)rect{
    
    CGFloat height = img.size.height;
    CGFloat width = img.size.width;
    //开启一个图形上下文
    UIGraphicsBeginImageContext(img.size);
    
    //在图片上下文中绘制图片
    [img drawInRect:CGRectMake(0, 0,width,height)];
    
    //在图片的指定位置绘制文字   -- 7.0以后才有这个方法
    [text drawInRect:rect withAttributes:atts];
    
    
    //从图形上下文拿到最终的图片
    UIImage *newImg = UIGraphicsGetImageFromCurrentImageContext();
    
    //关闭图片上下文
    UIGraphicsEndImageContext();
    
    return newImg;
}

调用

UIImage *end = [self addWaterText:@"hhhhh啊啊啊啊啊啊啊" Attributes:@{NSForegroundColorAttributeName:[UIColor redColor],NSFontAttributeName:font(15)} toImage:decodedImage rect:CGRectMake(0, 0, 90, 40)];
    self.imageView.image = end;