在 iOS 上将文本转换为图像

Converting Text to Image on iOS(在 iOS 上将文本转换为图像)

问题描述

如何将文本转换为图像并在 UIImageview 中显示.有谁知道从文本到图像的转换?

How to convert Text to Image and show in UIImageview. Can anyone know the conversion from Text to Image?

推荐答案

使用 Swift 5 和 iOS 12，您可以选择以下6种方式中的一种来解决您的问题.

With Swift 5 and iOS 12, you can choose one the 6 following ways in order to solve your problem.

在您想将 String 转换为具有某些属性的 UIImage 的最简单情况下，您可以使用 draw(at:withAttributes:).以下 Playground 代码展示了如何使用 draw(at:withAttributes:) 从 String 获取 UIImage:

In the simplest case where you want to convert a String to a UIImage with some attributes, you can use draw(at:withAttributes:). The following Playground codes show how to get an UIImage from a String using draw(at:withAttributes:):

import UIKit
import PlaygroundSupport

let text = "Hello, world"
let attributes = [
    NSAttributedString.Key.foregroundColor: UIColor.yellow,
    NSAttributedString.Key.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 = [
    NSAttributedString.Key.foregroundColor: UIColor.yellow,
    NSAttributedString.Key.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，称为 draw(at:).

Note that NSAttributedString has a similar method called draw(at:).

作为 draw(at:withAttributes:) 的替代方法，您可以使用 draw(in:withAttributes:).

As an alternative to draw(at:withAttributes:), you can use draw(in:withAttributes:).

import UIKit
import PlaygroundSupport

let text = "Hello, world"
let attributes = [
    NSAttributedString.Key.foregroundColor: UIColor.yellow,
    NSAttributedString.Key.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 = [
    NSAttributedString.Key.foregroundColor: UIColor.yellow,
    NSAttributedString.Key.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，称为 draw(in:).

Note that NSAttributedString has a similar method called draw(in:).

作为 draw(at:withAttributes:) 和 draw(in:) 的替代方法，您可以使用 draw(with:options:attributes:context:).请注意，Apple 对 draw(with:options:attributes:context:):

As an alternative to draw(at:withAttributes:) and draw(in:), you can use draw(with:options:attributes:context:). Note that Apple has some recommendations for draw(with:options:attributes:context:):

此方法默认使用基线原点.如果没有指定usesLineFragmentOrigin，矩形的高度将被忽略，该操作被认为是单线渲染.

This method uses the baseline origin by default. If usesLineFragmentOrigin is not specified, the rectangle’s height will be ignored and the operation considered to be single-line rendering.

import UIKit
import PlaygroundSupport

let text = "Hello, world"
let attributes = [
    NSAttributedString.Key.foregroundColor: UIColor.yellow,
    NSAttributedString.Key.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 = [
    NSAttributedString.Key.foregroundColor: UIColor.yellow,
    NSAttributedString.Key.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，称为 draw(with:options:context:).

Note that NSAttributedString has a similar method called draw(with:options:context:).

如果您想将 UILabel、UITextField 或 UITextView 的文本捕获到 UIImage，您可以使用 render(in:).以下 Playground 代码展示了如何使用 render(in:) 对 UILabel 的内容文本进行快照:

If you want to capture the text of a UILabel, UITextField or UITextView to a UIImage, you can use render(in:). The following Playground codes show how to snapshot the content text of a UILabel using render(in:):

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)

<小时>

#5.使用 UIView 的 drawHierarchy(in:afterScreenUpdates:) 方法

如果您想将 UILabel、UITextField 或 UITextView 的文本捕获到 UIImage，您可以使用 drawHierarchy(in:afterScreenUpdates:).请注意，Apple 对 drawHierarchy(in:afterScreenUpdates:) 有一些建议:

---

#5. Using UIView's drawHierarchy(in:afterScreenUpdates:) method

If you want to capture the text of a UILabel, UITextField or UITextView to a UIImage, you can use drawHierarchy(in:afterScreenUpdates:). Note that Apple has some recommendations for drawHierarchy(in:afterScreenUpdates:):

当您想要将图形效果(例如模糊)应用到视图快照时，请使用此方法.此方法不如 snapshotView(afterScreenUpdates:) 方法快.

Use this method when you want to apply a graphical effect, such as a blur, to a view snapshot. This method is not as fast as the snapshotView(afterScreenUpdates:) method.

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)

<小时>

#6.使用 UIView 的 snapshotView(afterScreenUpdates:) 方法

如果您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 代码展示了如何使用 snapshotView(afterScreenUpdates:) 将 UILabel 的内容文本快照到 UIView 中:

---

#6. Using UIView's snapshotView(afterScreenUpdates:) method

If it's OK for you to get a UIView instead of a UIImage from your snapshot operation, you can use snapshotView(afterScreenUpdates:). The following Playground code shows how to snapshot the content text of a UILabel into a UIView using snapshotView(afterScreenUpdates:):

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

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