app帮助里的长图设置

在app里有些帮助文档,是一张长长的图片,如何简单的设置呢

- (void)addImageView {
    //添加scrollview
    UIScrollView *scro = [[UIScrollView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:scro];
    
    //设置image
    UIImage *img = [UIImage imageNamed:@"help"];
    
    //获取图片像素
    CGFloat fixelW = CGImageGetWidth(img.CGImage);
    CGFloat fixelH = CGImageGetHeight(img.CGImage);

    CGFloat mainWidth = self.view.frame.size.width;
    CGFloat mainHeight = self.view.frame.size.width * fixelH/fixelW;
    
    //设置contentsize
    [scro setContentSize:CGSizeMake(mainWidth, mainHeight)];
    
    //设置imageview
    UIImageView *imgview = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, mainWidth, mainHeight)];
    [scro addSubview:imgview];
    imgview.image = img;
}