将文本转换为图像
如何将文本转换为图像并在UIImageView中显示。 任何人都可以知道从文本到图像的转换？
你可以开始玩这样的东西：
NSString *string = @"Some text"; UIGraphicsBeginImageContext(CGSizeMake(80, 50)); [string drawAtPoint:CGPointMake(10, 20) withFont:[UIFont systemFontOfSize:12]]; UIImage *result = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); result包含带有文本的UIImage，并且可以将其分配给UIImageView image属性。
使用Swift 4和iOS 11，您可以select以下六种方法之一来解决您的问题。
＃1。 使用NSString的draw(at:withAttributes:)方法
在最简单的情况下，你想用一些属性将String转换为UIImage ，你可以使用draw(at:withAttributes:) 。 下面的游乐场代码显示了如何使用draw(at:withAttributes:)从String获取UIImage ：
import UIKit import PlaygroundSupport let text = "Hello, world" let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.yellow, NSAttributedStringKey.font: UIFont.systemFont(ofSize: 22) ] let textSize = text.size(withAttributes: attributes) UIGraphicsBeginImageContextWithOptions(textSize, true, 0) text.draw(at: CGPoint.zero, withAttributes: attributes) let image = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() PlaygroundPage.current.liveView = UIImageView(image: image)
import UIKit import PlaygroundSupport let text = "Hello, world" let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.yellow, NSAttributedStringKey.font: UIFont.systemFont(ofSize: 22) ] let textSize = text.size(withAttributes: attributes) let renderer = UIGraphicsImageRenderer(size: textSize) let image = renderer.image(actions: { context in text.draw(at: CGPoint.zero, withAttributes: attributes) }) PlaygroundPage.current.liveView = UIImageView(image: image)
请注意， NSAttributedString有一个类似的方法叫做draw(at:) 。
＃2。 使用NSString的draw(in:withAttributes:)方法
作为draw(at:withAttributes:)的替代方法draw(at:withAttributes:) ，可以使用draw(in:withAttributes:) 。
import UIKit import PlaygroundSupport let text = "Hello, world" let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.yellow, NSAttributedStringKey.font: UIFont.systemFont(ofSize: 22) ] let textSize = text.size(withAttributes: attributes) UIGraphicsBeginImageContextWithOptions(textSize, true, 0) let rect = CGRect(origin: .zero, size: textSize) text.draw(in: rect, withAttributes: attributes) let image = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() PlaygroundPage.current.liveView = UIImageView(image: image)
import UIKit import PlaygroundSupport let text = "Hello, world" let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.yellow, NSAttributedStringKey.font: UIFont.systemFont(ofSize: 22) ] let textSize = text.size(withAttributes: attributes) let renderer = UIGraphicsImageRenderer(size: textSize) let image = renderer.image(actions: { context in let rect = CGRect(origin: .zero, size: textSize) text.draw(in: rect, withAttributes: attributes) }) PlaygroundPage.current.liveView = UIImageView(image: image)
请注意， NSAttributedString有一个类似的方法叫做draw(in:) 。
＃3。 使用NSString的draw(with:options:attributes:context:)方法
作为draw(at:withAttributes:)的替代方法draw(at:withAttributes:)和draw(in:) ，可以使用draw(with:options:attributes:context:) 。 请注意，苹果有一些关于draw(with:options:attributes:context:)build议draw(with:options:attributes:context:) ：
此方法默认使用基准原点。 如果没有指定
usesLineFragmentOrigin，矩形的高度将被忽略，操作被认为是单行渲染。
import UIKit import PlaygroundSupport let text = "Hello, world" let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.yellow, NSAttributedStringKey.font: UIFont.systemFont(ofSize: 22) ] let textSize = text.size(withAttributes: attributes) UIGraphicsBeginImageContextWithOptions(textSize, true, 0) let rect = CGRect(origin: .zero, size: textSize) text.draw(with: rect, options: [.usesLineFragmentOrigin], attributes: attributes, context: nil) let image = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() PlaygroundPage.current.liveView = UIImageView(image: image)
import UIKit import PlaygroundSupport let text = "Hello, world" let attributes = [ NSAttributedStringKey.foregroundColor: UIColor.yellow, NSAttributedStringKey.font: UIFont.systemFont(ofSize: 22) ] let textSize = text.size(withAttributes: attributes) let renderer = UIGraphicsImageRenderer(size: textSize) let image = renderer.image(actions: { context in text.draw(with: .zero, options: [.usesLineFragmentOrigin], attributes: attributes, context: nil) }) PlaygroundPage.current.liveView = UIImageView(image: image)
请注意， NSAttributedString有一个类似的方法叫做draw(with:options:context:) 。
＃4。 使用CALayer的render(in:)方法
如果要将UILabel ， UITextField或UITextView的文本捕获到UIImage ，则可以使用render(in:) 。 以下游乐场代码显示如何使用render(in:)快照UILabel的内容文本：
import UIKit import PlaygroundSupport let label = UILabel(frame: .zero) label.textColor = .yellow label.font = UIFont.systemFont(ofSize: 22) label.text = "Hello, world" label.sizeToFit() UIGraphicsBeginImageContextWithOptions(label.frame.size, true, 0) guard let context = UIGraphicsGetCurrentContext() else { exit(0) } label.layer.render(in: context) let image = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() PlaygroundPage.current.liveView = UIImageView(image: image)
import UIKit import PlaygroundSupport let label = UILabel(frame: .zero) label.textColor = .yellow label.font = UIFont.systemFont(ofSize: 22) label.text = "Hello, world" label.sizeToFit() let renderer = UIGraphicsImageRenderer(size: label.frame.size) let image = renderer.image(actions: { context in label.layer.render(in: context.cgContext) }) PlaygroundPage.current.liveView = UIImageView(image: image)
＃5。 使用UIView的drawHierarchy(in:afterScreenUpdates:)方法
如果要将UILabel ， UITextField或UITextView的文本捕获到UIImage ，可以使用drawHierarchy(in:afterScreenUpdates:) 。 请注意，苹果有一些build议drawHierarchy(in:afterScreenUpdates:) ：
如果要将graphics效果（如模糊效果）应用于视图快照，请使用此方法。 这个方法不如
snapshotView(afterScreenUpdates:)方法快。
import UIKit import PlaygroundSupport let label = UILabel(frame: .zero) label.textColor = .yellow label.font = UIFont.systemFont(ofSize: 22) label.text = "Hello, world" label.sizeToFit() UIGraphicsBeginImageContextWithOptions(label.frame.size, true, 0) _ = label.drawHierarchy(in: label.bounds, afterScreenUpdates: true) let image = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() PlaygroundPage.current.liveView = UIImageView(image: image)
import UIKit import PlaygroundSupport let label = UILabel(frame: .zero) label.textColor = .yellow label.font = UIFont.systemFont(ofSize: 22) label.text = "Hello, world" label.sizeToFit() let renderer = UIGraphicsImageRenderer(size: label.frame.size) let image = renderer.image(actions: { context in _ = label.drawHierarchy(in: label.bounds, afterScreenUpdates: true) }) PlaygroundPage.current.liveView = UIImageView(image: image)
＃6。 使用UIView的snapshotView(afterScreenUpdates:)方法
如果可以从快照操作中获取UIView而不是UIImage ，则可以使用snapshotView(afterScreenUpdates:) 。 以下Playground代码显示如何使用snapshotView(afterScreenUpdates:)将UILabel的内容文本快照到UIView ：
import UIKit import PlaygroundSupport let label = UILabel(frame: .zero) label.textColor = .yellow label.font = UIFont.systemFont(ofSize: 22) label.text = "Hello, world" label.sizeToFit() let view = label.snapshotView(afterScreenUpdates: true) PlaygroundPage.current.liveView = view
[yourImageView addSubview：textView]; [canvas addSubview：passingImageView];
UIGraphicsBeginImageContext(canvas.bounds.size); [canvas.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return resultingImage;
你应该把UIView和里面拿UIImageview和上面的代码应该做的trick.Herecanvas是UIView。
SWIFT 3：
为UIImage创build一个扩展，以便您可以在任何地方使用它：
extension UIImage { class func imageWithLabel(label: UILabel) -> UIImage { UIGraphicsBeginImageContextWithOptions(label.bounds.size, false, 0.0) label.layer.render(in: UIGraphicsGetCurrentContext()!) let img = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return img! } }
现在，您需要使用此function从文本创build图像：
//这个标签的自定义是根据你的需要select哪种字体，你需要什么背景颜色。 随意更改。
let label = UILabel(frame: CGRect(x: 0, y: 0, width: 300, height: 20)) label.numberOfLines = 0 label.textAlignment = .center label.textColor = UIColor.white label.backgroundColor = UIColor.black label.font = UIFont(name: "Montserrat", size: 17) label.text = "YOUR TEXT HERE" label.sizeToFit() let image = UIImage.imageWithLabel(label: label)