NSAttributedString：适应容器的图片

Question

NSAttributedString：适应容器的图片

htmliosimageswiftnsattributedstring

12

我有一个NSAttributedString，它是由HTML创建的，并显示一些图片。问题是这些图片比容器大，我想知道如何让它们适应其中。

谢谢你的帮助

- Florentin

3个回答

8

Swift 4.2：采用 @Nic Hubbard 的方法

let htmlString = "Put Your YourHTML String Here"

let setHeightUsingCSS = "<head><style type=\"text/css\"> img{ max-height: 100%; max-width: \(self.textView.frame.size.width) !important; width: auto; height: auto;} </style> </head><body> \(htmlString) </body>"

self.textView.attributedText = setHeightUsingCSS.html2AttributedString


extension Data {
    var html2AttributedString: NSAttributedString? {
        do {
            return try NSAttributedString(data: self, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil)
        } catch {
            print("error:", error)
            return  nil
        }
    }
    var html2String: String {
        return html2AttributedString?.string ?? ""
    }
}

extension String {
    var html2AttributedString: NSAttributedString? {
        return Data(utf8).html2AttributedString
    }
    var html2String: String {
        return html2AttributedString?.string ?? ""
    }
}

扩展参考

- ZAFAR007

我已经尝试了上述方法，但解决方案并没有奏效，图像仍然超出屏幕。 - Prashanth

@Prashanth，我更新了我的答案。我忘记添加 !important 和 }。请再试一次，它在我的应用程序上运行正常。 - ZAFAR007

4

您还可以将字符串包装在完整的HTML文档中，使用 CSS 调整图片大小。

- Nic Hubbard

1

不，不是NSAttributesString。在head标签中包含整个HTML文档和CSS。 - Nic Hubbard

哦，显然！谢谢。 - Florentin

@NicHubbard，你能提供一个CSS调整图片大小的例子吗？ - Giorgio

1

@Giorgio 使用 img {max-width: %fpx; height: auto; text-align:center;} 并使用屏幕边界来设置 max-width。 - Nic Hubbard

某种方式，max-width：100％未能奏效......但其他属性如颜色可以，例如 <style>div { color: red !important;}</style>。 - Hardik Darji

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- Florentin · Accepted Answer

我终于找到了怎样做：

content.enumerateAttribute(NSAttachmentAttributeName, inRange: NSMakeRange(0, content.length), options: NSAttributedStringEnumerationOptions(0)) { (value, range, stop) -> Void in
    if let attachement = value as? NSTextAttachment {
        let image = attachement.imageForBounds(attachement.bounds, textContainer: NSTextContainer(), characterIndex: range.location)
        let screenSize: CGRect = UIScreen.mainScreen().bounds
        if image.size.width > screenSize.width-2 {
            let newImage = image.resizeImage((screenSize.width-2)/image.size.width)
            let newAttribut = NSTextAttachment()
            newAttribut.image = newImage
            content.addAttribute(NSAttachmentAttributeName, value: newAttribut, range: range)
        }
    }
}

函数resizeImage()的定义如下：

extension UIImage {
    func resizeImage(scale: CGFloat) -> UIImage {
        let newSize = CGSizeMake(self.size.width*scale, self.size.height*scale)
        let rect = CGRectMake(0, 0, newSize.width, newSize.height)

        UIGraphicsBeginImageContext(newSize)
        self.drawInRect(rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

Swift 3 版本

text.enumerateAttribute(NSAttachmentAttributeName, in: NSMakeRange(0, text.length), options: .init(rawValue: 0), using: { (value, range, stop) in
    if let attachement = value as? NSTextAttachment {
        let image = attachement.image(forBounds: attachement.bounds, textContainer: NSTextContainer(), characterIndex: range.location)!
        let screenSize: CGRect = UIScreen.main.bounds
        if image.size.width > screenSize.width-20 {
            let newImage = image.resizeImage(scale: (screenSize.width-2)/image.size.width)
            let newAttribut = NSTextAttachment()
            newAttribut.image = newImage
            text.addAttribute(NSAttachmentAttributeName, value: newAttribut, range: range)
        }
    }
})

函数resizeImage()的定义如下：

func resizeImage(scale: CGFloat) -> UIImage {
    let newSize = CGSize(width: self.size.width*scale, height: self.size.height*scale)
    let rect = CGRect(origin: CGPoint.zero, size: newSize)

    UIGraphicsBeginImageContext(newSize)
    self.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage!
}

Swift 4 版本 + 扩展和可自定义的图片最大宽度

extension NSAttributedString {
    func attributedStringWithResizedImages(with maxWidth: CGFloat) -> NSAttributedString {
        let text = NSMutableAttributedString(attributedString: self)
        text.enumerateAttribute(NSAttributedStringKey.attachment, in: NSMakeRange(0, text.length), options: .init(rawValue: 0), using: { (value, range, stop) in
            if let attachement = value as? NSTextAttachment {
                let image = attachement.image(forBounds: attachement.bounds, textContainer: NSTextContainer(), characterIndex: range.location)!
                if image.size.width > maxWidth {
                    let newImage = image.resizeImage(scale: maxWidth/image.size.width)
                    let newAttribut = NSTextAttachment()
                    newAttribut.image = newImage
                    text.addAttribute(NSAttributedStringKey.attachment, value: newAttribut, range: range)
                }
            }
        })
        return text
    }
}

extension UIImage {
    func resizeImage(scale: CGFloat) -> UIImage {
        let newSize = CGSize(width: self.size.width*scale, height: self.size.height*scale)
        let rect = CGRect(origin: CGPoint.zero, size: newSize)

        UIGraphicsBeginImageContext(newSize)
        self.draw(in: rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage!
    }
}