如何在不损失视网膜显示质量的情况下将UIView捕获到UIImage

我的代码对普通设备工作正常，但在视网膜设备上创build模糊的图像。

有没有人知道我的问题的解决scheme？ 

+ (UIImage *) imageWithView:(UIView *)view { UIGraphicsBeginImageContext(view.bounds.size); [view.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage * img = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return img; }

从使用UIGraphicsBeginImageContext切换到UIGraphicsBeginImageContextWithOptions （如本页所述 ）。 传递0.0作为比例（第三个参数），你将得到一个缩放因子等于屏幕的上下文。

UIGraphicsBeginImageContext使用1.0的固定比例因子，所以实际上iPhone 4上的图像与其他iPhone上的图像完全相同。 我敢打赌，iPhone 4正在应用一个filter，当你隐式地扩展它，或者只是你的大脑接近它而不是周围的一切。

所以，我猜： 

 #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; }

而在迅捷4： 

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

目前接受的答案现在已经过时，至less如果你是支持iOS 7的话。

如果您只支持iOS7 +，则应该使用以下内容： 

 + (UIImage *) imageWithView:(UIView *)view { UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0f); [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:NO]; UIImage * snapshotImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return snapshotImage; }

根据这篇文章 ，你可以看到，新的iOS7方法drawViewHierarchyInRect:afterScreenUpdates:比renderInContext:要快很多倍。 基准http://f.cl.ly/items/323c000h013V2f3R2p3b/Screen%20Shot%202013-09-16%20at%2001.12.37%20.png

我已经基于@Dima解决scheme创build了一个Swift扩展： 

 extension UIImage { class func imageWithView(view: UIView) -> UIImage { UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0) view.drawViewHierarchyInRect(view.bounds, afterScreenUpdates: true) let img = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return img } }

用法 

 let view = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100)) let image = UIImage.imageWithView(view)

要通过@Tommy和@Dima改进答案，请使用以下类别将UIView呈现为具有透明背景的 UIImage ，并且不会损失质量。 在iOS7上工作。 （或者只是在实现中重用该方法，用图像replaceself引用）

UIView的+ RenderViewToImage.h 

 #import <UIKit/UIKit.h> @interface UIView (RenderToImage) - (UIImage *)imageByRenderingView; @end

UIView的+ RenderViewToImage.m 

 #import "UIView+RenderViewToImage.h" @implementation UIView (RenderViewToImage) - (UIImage *)imageByRenderingView { UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, 0.0); [self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES]; UIImage * snapshotImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return snapshotImage; } @end

Swift 3

Swift 3解决scheme（基于Dima的答案 ）和UIView扩展应该是这样的： 

 extension UIView { public func getSnapshotImage() -> UIImage { UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.isOpaque, 0) self.drawHierarchy(in: self.bounds, afterScreenUpdates: false) let snapshotImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()! UIGraphicsEndImageContext() return snapshotImage } }

iOS版迅速

使用现代的UIGraphicsImageRenderer 

 public extension UIView { @available(iOS 10.0, *) public func renderToImage(afterScreenUpdates: Bool = false) -> UIImage { let rendererFormat = UIGraphicsImageRendererFormat.default() rendererFormat.opaque = isOpaque let renderer = UIGraphicsImageRenderer(size: bounds.size, format: rendererFormat) let snapshotImage = renderer.image { _ in drawHierarchy(in: bounds, afterScreenUpdates: afterScreenUpdates) } return snapshotImage } }

Swift 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) }

Swift 3.0的实现 

 extension UIView { func getSnapshotImage() -> UIImage { UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0) drawHierarchy(in: bounds, afterScreenUpdates: false) let snapshotImage = UIGraphicsGetImageFromCurrentImageContext()! UIGraphicsEndImageContext() return snapshotImage } }

所有斯威夫特3答案没有为我工作，所以我已经翻译了最接受的答案： 

 extension UIImage { class func imageWithView(view: UIView) -> UIImage { UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.isOpaque, 0.0) view.layer.render(in: UIGraphicsGetCurrentContext()!) let img: UIImage? = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return img! } }

embedded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
  • 请注意使用延迟来简化上下文清理。
  • 也将应用视图的不透明度和当前比例。
  • 没有东西只是解开使用! 这可能会导致崩溃。 
 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() } } }

有时候drawRect方法会造成问题，所以我得到了更合适的答案。 你也可以看看它捕获UIView的UIImage卡在DrawRect方法 

 - (UIImage*)screenshotForView:(UIView *)view { UIGraphicsBeginImageContext(view.bounds.size); [view.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); // hack, helps w/ our colors when blurring NSData *imageData = UIImageJPEGRepresentation(image, 1); // convert to jpeg image = [UIImage imageWithData:imageData]; return image; }

在这个方法中只传递一个视图对象，它将返回一个UIImage对象。 

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

将此添加到UIView类别的方法 

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