类似长图截屏分享的功能
把整个view给完整的截下来，做成一张图片。

-(UIImage *)getImageWithFullScreenshot   
{    
    BOOL ignoreOrientation = SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0");    
        
    UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;    
        
    CGSize imageSize = CGSizeZero;    
    if (UIInterfaceOrientationIsPortrait(orientation) || ignoreOrientation)    
        imageSize = [UIScreen mainScreen].bounds.size;    
    else    
        imageSize = CGSizeMake([UIScreen mainScreen].bounds.size.height, [UIScreen mainScreen].bounds.size.width);    
        
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, [UIScreen mainScreen].scale);    
    CGContextRef context = UIGraphicsGetCurrentContext();    
        
    for (UIWindow *window in [[UIApplication sharedApplication] windows])    
    {    
        CGContextSaveGState(context);    
        CGContextTranslateCTM(context, window.center.x, window.center.y);    
        CGContextConcatCTM(context, window.transform);    
        CGContextTranslateCTM(context, -window.bounds.size.width * window.layer.anchorPoint.x, -window.bounds.size.height * window.layer.anchorPoint.y);    
            
        // Correct for the screen orientation    
        if(!ignoreOrientation)    
        {    
            if(orientation == UIInterfaceOrientationLandscapeLeft)    
            {    
                CGContextRotateCTM(context, (CGFloat)M_PI_2);    
                CGContextTranslateCTM(context, 0, -imageSize.width);    
            }    
            else if(orientation == UIInterfaceOrientationLandscapeRight)    
            {    
                CGContextRotateCTM(context, (CGFloat)-M_PI_2);    
                CGContextTranslateCTM(context, -imageSize.height, 0);    
            }    
            else if(orientation == UIInterfaceOrientationPortraitUpsideDown)    
            {    
                CGContextRotateCTM(context, (CGFloat)M_PI);    
                CGContextTranslateCTM(context, -imageSize.width, -imageSize.height);    
            }    
        }    
            
        if([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)])    
            [window drawViewHierarchyInRect:window.bounds afterScreenUpdates:NO];    
        else    
            [window.layer renderInContext:UIGraphicsGetCurrentContext()];    
            
        CGContextRestoreGState(context);    
    }    
        
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();    
        
    UIGraphicsEndImageContext();    
        
    return image;    
}