从使用UIGraphicsBeginImageContext切换到使用UIGraphicsBeginImageContextWithOptions(如本页所述)。通过0.0进行缩放(第三个参数)，您将获得一个缩放因子与屏幕的缩放因子相等的上下文。

UIGraphicsBeginImageContext使用了一个固定的缩放因子1.0，所以你实际上在iPhone 4和其他iPhone上得到了完全相同的图像。我敢打赌，要么是iPhone 4在你隐式放大它的时候应用了一个过滤器，要么就是你的大脑发现它比周围的所有东西都更不清晰。

所以，我想:

#import <QuartzCore/QuartzCore.h>

+ (UIImage *)imageWithView:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return img;
}

在Swift 4中:

func image(with view: UIView) -> UIImage? {
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.isOpaque, 0.0)
    defer { UIGraphicsEndImageContext() }
    if let context = UIGraphicsGetCurrentContext() {
        view.layer.render(in: context)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        return image
    }
    return nil
}

斯威夫特2.0:

使用扩展方法:

extension UIImage{

   class func renderUIViewToImage(viewToBeRendered:UIView?) -> UIImage
   {
       UIGraphicsBeginImageContextWithOptions((viewToBeRendered?.bounds.size)!, false, 0.0)
       viewToBeRendered!.drawViewHierarchyInRect(viewToBeRendered!.bounds, afterScreenUpdates: true)
       viewToBeRendered!.layer.renderInContext(UIGraphicsGetCurrentContext()!)

       let finalImage = UIGraphicsGetImageFromCurrentImageContext()
       UIGraphicsEndImageContext()

       return finalImage
   }

}

用法:

override func viewDidLoad() {
    super.viewDidLoad()

    //Sample View To Self.view
    let sampleView = UIView(frame: CGRectMake(100,100,200,200))
    sampleView.backgroundColor =  UIColor(patternImage: UIImage(named: "ic_120x120")!)
    self.view.addSubview(sampleView)    

    //ImageView With Image
    let sampleImageView = UIImageView(frame: CGRectMake(100,400,200,200))

    //sampleView is rendered to sampleImage
    var sampleImage = UIImage.renderUIViewToImage(sampleView)

    sampleImageView.image = sampleImage
    self.view.addSubview(sampleImageView)

 }

从使用UIGraphicsBeginImageContext切换到使用UIGraphicsBeginImageContextWithOptions(如本页所述)。通过0.0进行缩放(第三个参数)，您将获得一个缩放因子与屏幕的缩放因子相等的上下文。

UIGraphicsBeginImageContext使用了一个固定的缩放因子1.0，所以你实际上在iPhone 4和其他iPhone上得到了完全相同的图像。我敢打赌，要么是iPhone 4在你隐式放大它的时候应用了一个过滤器，要么就是你的大脑发现它比周围的所有东西都更不清晰。

所以，我想:

#import <QuartzCore/QuartzCore.h>

+ (UIImage *)imageWithView:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return img;
}

在Swift 4中:

func image(with view: UIView) -> UIImage? {
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.isOpaque, 0.0)
    defer { UIGraphicsEndImageContext() }
    if let context = UIGraphicsGetCurrentContext() {
        view.layer.render(in: context)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        return image
    }
    return nil
}

插入式Swift 3.0扩展，支持新的iOS 10.0 API和以前的方法。

注意:

iOS版本检查 注意使用defer来简化上下文清理。 还将应用视图的不透明度和当前比例。 没有任何东西只是使用!这可能会导致坠机。

extension UIView
{
    public func renderToImage(afterScreenUpdates: Bool = false) -> UIImage?
    {
        if #available(iOS 10.0, *)
        {
            let rendererFormat = UIGraphicsImageRendererFormat.default()
            rendererFormat.scale = self.layer.contentsScale
            rendererFormat.opaque = self.isOpaque
            let renderer = UIGraphicsImageRenderer(size: self.bounds.size, format: rendererFormat)

            return
                renderer.image
                {
                    _ in

                    self.drawHierarchy(in: self.bounds, afterScreenUpdates: afterScreenUpdates)
                }
        }
        else
        {
            UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.isOpaque, self.layer.contentsScale)
            defer
            {
                UIGraphicsEndImageContext()
            }

            self.drawHierarchy(in: self.bounds, afterScreenUpdates: afterScreenUpdates)

            return UIGraphicsGetImageFromCurrentImageContext()
        }
    }
}

将此添加到UIView Category的方法

- (UIImage*) capture {
    UIGraphicsBeginImageContext(self.bounds.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [self.layer renderInContext:context];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;
}

在这个方法中，只需要传递一个view对象它就会返回一个UIImage对象。

-(UIImage*)getUIImageFromView:(UIView*)yourView
{
 UIGraphicsBeginImageContext(yourView.bounds.size);
 [yourView.layer renderInContext:UIGraphicsGetCurrentContext()];
 UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 return image;
}