图片水印

往图片上加文字

    UIImage *oldImage = [UIImage imageNamed:@"1.jpg"];
    //上下文
    UIGraphicsBeginImageContextWithOptions(oldImage.size, NO, 0.0);
    //从零点开始画图
    [oldImage drawAtPoint:CGPointZero];
    //添加的文字
    NSString *text = @"老板,我要加薪!";
    //设定字体大小和颜色
    NSDictionary *dict = @{NSFontAttributeName:[UIFont systemFontOfSize:38],NSForegroundColorAttributeName:[UIColor redColor]};
    //设定要添加字体的位置
    [text drawAtPoint:CGPointMake(400, 533) withAttributes:dict];
    //得到新的图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    //关闭上下文
    UIGraphicsEndImageContext();
     _headerImageView.image = newImage;
    //将生成的新的图片转化为data并
    NSData *data = UIImagePNGRepresentation(newImage);
    //写到桌面
    [data writeToFile:@"/Users/aa/Desktop/Image.jpg" atomically:YES];

图片裁剪

裁剪圆形图片并在圆形周围加一个宽度为5的蓝色圆环

    UIImage *oldImage = [UIImage imageNamed:@"4"];
    //圆环的宽度
    CGFloat borderW = 5;
    //大图片的宽度和高度
    CGFloat imageW = oldImage.size.width + 2*borderW;
    CGFloat imageH = oldImage.size.height + 2*borderW;
    //防止有锯齿现象
    CGFloat circirW = imageW > imageH ? imageH : imageW;
    //开启上下文
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(circirW, circirW), NO, 0.0);
    //画个大的圆
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0,0, circirW, circirW)];
    //获取当前上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    //添加到上下文
    CGContextAddPath(ctx, path.CGPath);
    //渲染蓝色
    [[UIColor blueColor] set];
    //填充
    CGContextFillPath(ctx);
    //小圆的正切矩形
    CGRect clipR = CGRectMake(borderW, borderW, oldImage.size.width, oldImage.size.height);
    //画小圆
    UIBezierPath *clipPath = [UIBezierPath bezierPathWithOvalInRect:clipR];
    //设置裁剪区域
    [clipPath addClip];
    //画图片
    [oldImage drawAtPoint:CGPointMake(borderW, borderW)];
    //获取到新的图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    //关闭上下文
    UIGraphicsEndImageContext();
    _headerImage.image = newImage;