iOS有关截图的操作

 //根据size大小创建一个基于位图的图形上下文
    CGRect rect =view.frame;
    
    UIGraphicsBeginImageContext(rect.size);//根据size大小创建一个基于位图的图形上下文
    CGContextRef context = UIGraphicsGetCurrentContext();//获取上下文环境
    [view.layer renderInContext:context];//将要截取的view 映射到画布上
   
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext(); //获得图片
    UIGraphicsEndImageContext();
    imgvc.image = img;
    [view setHidden:YES];

 //根据 底层的imageview 大笑 来创建 画布
    UIGraphicsBeginImageContext(imgVC_bg.image.size);
    
    for (UIImageView *imgvc in array_imageView) {
        UIImage *img=imgvc.image;
        //画要添加到imgvc上的img
        [img drawInRect:CGRectMake(imgvc.frame.origin.x/double_proportion,(imgvc.frame.origin.y-64)/double_proportion,imgvc.frame.size.width/double_proportion,imgvc.frame.size.height/double_proportion)];
        [imgvc removeFromSuperview];
    }
    //在画底层imgvc，这样就会把img 添加到imgvc上来。
    [imgVC_bg.image drawInRect:CGRectMake(0, 0, imgVC_bg.image.size.width, imgVC_bg.image.size.height)];
    
    //形成新的image
    CGImageRef NewMergeImg = CGImageCreateWithImageInRect(UIGraphicsGetImageFromCurrentImageContext().CGImage,
                                                          CGRectMake(0, 0, imgVC_bg.image.size.width, imgVC_bg.image.size.height));
    UIGraphicsEndImageContext();