iOS：quartz2D绘图（处理图像,绘制图像并添加水印）

- (IBAction)drawImage:(UIButton *)sender
{
    //开始图像绘制的上下文
    UIGraphicsBeginImageContext(self.imageView.frame.size);
    
    //获取当前图形绘制的上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    //绘制一个矩形
    CGContextAddRect(context, CGRectMake(100, 100, 100, 100));
    
    //设置绘制属性
    [[UIColor redColor]set];
    
    //绘制路径
    CGContextDrawPath(context, kCGPathEOFillStroke);
    
    //从图像绘制上下文获取图片
    self.image = UIGraphicsGetImageFromCurrentImageContext();
    
    //结束图像绘制的上下文
    UIGraphicsEndImageContext();
    
    //显示图像绘制的上下文
    [self.imageView setImage:self.image];
}

- (IBAction)addWaterMark:(UIButton *)sender
{
    //开始图形绘制上下文
    UIGraphicsBeginImageContext(self.imageView.frame.size);
    
    //绘制图片
    UIImage *imageface = [UIImage imageNamed:@"2"];
    [imageface drawInRect:self.imageView.bounds];
    
    //绘制水印
    NSString *str = @"Wellcome to BeiJing";
    [str drawAtPoint:CGPointMake(50, 40) withAttributes:@{NSForegroundColorAttributeName:[UIColor blackColor],NSFontAttributeName:[UIFont systemFontOfSize:18]}];
    
    //从当前上下文获取图片
    self.image = UIGraphicsGetImageFromCurrentImageContext();
    
    //结束图像绘制上下文
    UIGraphicsEndImageContext();
    
    //显示带水印的图片
    [self.imageView setImage:self.image];
}

- (IBAction)saveImage:(UIButton *)sender
{
//    //设置图片保存的路径
//    NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
//    NSString *doucument = [documents lastObject];
//    NSLog(@"%@",doucument);
//
//    //拼接文件路径
//    NSString *fileName = [doucument stringByAppendingPathComponent:@"watermark.png"];
//    
//    //获取图片中的data
//    NSData *imageData = UIImagePNGRepresentation(self.image);
//    
//    //将图片数据写入沙盒文件保存起来
//    [imageData writeToFile:fileName atomically:YES];
    
    
    //保存到相册
    UIImageWriteToSavedPhotosAlbum(self.image, nil, nil, nil);
}