iOS 截图并放大, 不损失精度

截取view 并放大到指定倍数, 不损失精度

- (UIImage *)imageFromView: (UIView *) theView
{
    CGSize size = self.mainView.frame.size;
    CGFloat scale = 3.375f;
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
        scale = 3.375f;
        size = CGSizeApplyAffineTransform(size, CGAffineTransformMakeScale(scale, scale));
    }

    UIGraphicsBeginImageContext(size);

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(context, scale, scale);

    [self.view.layer renderInContext:context];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return viewImage;
}

即可得到指定倍数的分辨率的图片, 不会造成只能获得最高为屏幕分辨率大小的图片拉伸之后的结果