使用 Itext7 html pdf 在 PDF 中创建隐藏（仅限屏幕阅读器）文本

Question

我正在尝试将文本添加到我的 pdf 中，该文本只能由屏幕阅读器查看。该 pdf 包含一个将负数（即 -4.565）转换为 (4.565) - 红色的表格。当我使用屏幕阅读器时，它只读取 4.565，我想预先添加负值。

我尝试过使用 aria-label、aria-live 并创建一个由于文本颜色等原因而不可见的 html 属性

Answer 1

我知道怎么做了。我必须使用convertToElements()，而不是我最初使用的convertToDocument()。

然后您可以递归地遍历元素列表，直到找到需要更改的描述，并在元素上调用 .GetAccessibilityProperties().SetAlternativeDescription("Screen reader only") 。您还必须首先将元素转换为其类型。 （段落）element.GetAccess...

    private string recurse(IList<iText.Layout.Element.IElement> elements, string previous, Document document)
    {
        string result = "";  
        // variable that get sent back that is the string of the content so that .SetAlternateDescription() can be called with the content

        foreach (iText.Layout.Element.IElement element in elements)
        {
            var elementType = element.GetType().Name;

            // I am only going through tables but it could be anything
            if (elementType == "Table")
            {
                Table table = (Table)element;
                IList<iText.Layout.Element.IElement> children = ((IAbstractElement)element).GetChildren();
                recurse(children, "Table", document); 
                document.Add(table);  
                // Add the most complex form, dont add children
            }
            else if (elementType == "Cell")
            {
                string content = recurse(((IAbstractElement)element).GetChildren(), "Cell", document);
                if (content.Length > 0)  // check to see that I need to set Description
                    ((Cell)element).GetAccessibilityProperties().SetAlternateDescription("SCREEN READER ONLY READS THIS STRING, NOT VISIBLE IN PDF:" + content);
            }
            else if (elementType == "Paragraph" && previous == "Cell")
            {
                result += recurse(((IAbstractElement)element).GetChildren(), "Cell-Paragraph", document); 
                // cell-paragraph to show the element came from a table -> paragraph and not div -> paragraph
            }
            else if (elementType == "Text" && previous == "Cell-Paragraph")
            {
                Text textElement = (Text)element;
                string content = textElement.GetText();
                return content;
                // This is where the actual string content is
            }
            else if(previous.Length == 0) // Add other elements, only when they are the parent element
            {
                Paragraph paragraphElement = element as Paragraph;
                if (paragraphElement != null)
                    document.Add(paragraphElement);
                Div divElement = element as Div;
                if (divElement != null)
                    document.Add(divElement);
            }
        }
        return result;
    }