在iOS上将文本转换为图像

时间：2009-10-28 10:49:29

标签： ios image text uiimageview rendering

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吗？

4 个答案:

答案 0 :(得分：11)

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，您可以将其分配给UIImageView image属性。

答案 1 :(得分：7)

使用Swift 5和iOS 12，您可以选择以下6种方式，以解决您的问题。

＃1。使用NSString＆＃39; draw(at:withAttributes:)方法

在您希望将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:)。以下操场代码显示如何使用UIImage从String获取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有一个名为draw(at:)的类似方法。

＃2。使用NSString＆＃39; draw(in:withAttributes:)方法

作为draw(at:withAttributes:)的替代方案，您可以使用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有一个名为draw(in:)的类似方法。

＃3。使用NSString＆＃39; draw(with:options:attributes:context:)方法

作为draw(at:withAttributes:)和draw(in:)的替代方案，您可以使用draw(with:options:attributes:context:)。请注意，Apple对draw(with:options:attributes:context:)提出了一些建议：

  

此方法默认使用基线原点。   如果未指定usesLineFragmentOrigin，则将忽略矩形的高度，并将操作视为单行渲染。

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有一个名为draw(with:options:context:)的类似方法。

＃4。使用CALayer＆＃39; render(in:)方法

如果您要将UILabel，UITextField或UITextView的文字捕获到UIImage，可以使用render(in:)。以下操场代码显示如何使用UILabel对render(in:)的内容文本进行快照：

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＆＃39; drawHierarchy(in:afterScreenUpdates:)方法

如果您要将UILabel，UITextField或UITextView的文字捕获到UIImage，可以使用drawHierarchy(in:afterScreenUpdates:)。请注意，Apple对drawHierarchy(in:afterScreenUpdates:)提出了一些建议：

  

如果要将图形效果（如模糊）应用于视图快照，请使用此方法。此方法不如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＆＃39; snapshotView(afterScreenUpdates:)方法

如果您可以从快照操作中获得UIView而不是UIImage，则可以使用snapshotView(afterScreenUpdates:)。以下Playground代码显示了如何使用UILabel将UIView的内容文本快照到snapshotView(afterScreenUpdates:)中：

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

答案 2 :(得分：1)

SWIFT 3：

为UIImage创建一个扩展，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!
   }
}

现在您需要使用它来从Text：

创建图像

//此标签的自定义根据您的需要而定，您需要哪种字体，背景颜色。随意改变。

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)

答案 3 :(得分：0)

[yourImageView addSubview：textView];     [canvas addSubview：passingImageView]; 

UIGraphicsBeginImageContext(canvas.bounds.size);
[canvas.layer renderInContext:UIGraphicsGetCurrentContext()];

UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();
return resultingImage;

你应该拿一个UIView并在里面拿UIImageview，上面的代码应该可以解决这个问题。这个画布是UIView。

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