IOS 实现截图功能

-(UIImage *)saveImage:(UIView *)view withRect:(CGRect) mainRect // mainRect 应该是相对于屏幕的Rect
{
    UIGraphicsBeginImageContext(mainRect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [[UIColor blackColor] set];

    CGContextFillRect(context, mainRect);
    [view.layer renderInContext:context];

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newImage;
}