wen Latex公式导出word，Latex转换MathML使用POI导出公式可编辑的Word文件
背景
之前在 使用spire.doc导出支持编辑Latex公式的标准格式word 博客中写过，使用spire.doc来生成word，不得不说spire.doc的api操作起来还是比较方便，但是使用的过程中还是发生了一些异常，如∑求和公式会报错，类似 limit widehat sideset overline leqslant geqslant extcircled 均遇到了问题，类似解析失败无法渲染、求和公式设置上下限报空指针异常等，使用同样的方式转换MathML之后还是同样的问题，无法解决，一个两个还能以图片的形式显示，随着这么多问题的出现，终究不是办法
POI导出Latex至word
POI转Latex转WORD过程是 Latex → MathML(数学标记语言) → OMML(Word公式)
Latex转MathML问题
POI支持MathML，我基本上生成的都是数学试卷，Latex公式有了，但是需要转换为MathML，一开始准备使用fmath三件套，这里需要吐槽一下，这个官网的下载链接已经失效，搜了一下看到很久没去的CSDN有资源，一下载50积分没了，貌似不管啥资源都是50分起步，看来CSDN已经不是我等P民可以混迹的存在了
但是实验了一下，fmath导出的复杂公式在word中显示偶尔有问题，可能是因为版本太老了，在StackOverflow上看到有人推荐使用snuggletex-core这个类库，我就更换了实现方式，我来找了大量的数学公式latex，先看下效果
POM依赖
<!-- https://mvnrepository.com/artifact/de.rototor.snuggletex/snuggletex-core -->
<dependency>
<groupId>de.rototor.snuggletex</groupId>
<artifactId>snuggletex-core</artifactId>
<version>1.3.0</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>4.1.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.poi/ooxml-schemas -->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>ooxml-schemas</artifactId>
<version>1.4</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>4.1.2</version>
</dependency>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.11.0</version>
</dependency>
snuggletex-core转换Latex为MathML
注意：这里的latex必须用$$包裹，否则在转换MathML的时候会报错
@SneakyThrows
public static void addLatex(String latex, XWPFParagraph paragraph) {
paragraph.setAlignment(ParagraphAlignment.LEFT);
paragraph.setFontAlignment(ParagraphAlignment.LEFT.getValue());
SnuggleEngine engine = new uk.ac.ed.ph.snuggletex.SnuggleEngine();
SnuggleSession session = engine.createSession();
SnuggleInput input = new uk.ac.ed.ph.snuggletex.SnuggleInput(latex);
session.parseInput(input);
String mathML = session.buildXMLString();
CTOMath ctOMath = getOMML(mathML);
CTP ctp = paragraph.getCTP();
CTOMath ctoMath = ctp.addNewOMath();
ctoMath.set(ctOMath);
}
MathML转OMML
MML2OMML.XSL在windows的Office安装目录里面直接搜就能拿到
private static File stylesheet = new File("D:\MML2OMML.XSL");
private static TransformerFactory tFactory = TransformerFactory.newInstance();
private static StreamSource stylesource = new StreamSource(stylesheet);
private static CTOMath getOMML(String mathML) throws Exception {
Transformer transformer = tFactory.newTransformer(stylesource);
StringReader stringreader = new StringReader(mathML);
StreamSource source = new StreamSource(stringreader);
StringWriter stringwriter = new StringWriter();
StreamResult result = new StreamResult(stringwriter);
transformer.transform(source, result);
String ooML = stringwriter.toString();
stringwriter.close();
CTOMathPara ctOMathPara = CTOMathPara.Factory.parse(ooML);
CTOMath ctOMath = ctOMathPara.getOMathArray(0);
//for making this to work with Office 2007 Word also, special font settings are necessary
XmlCursor xmlcursor = ctOMath.newCursor();
while (xmlcursor.hasNextToken()) {
XmlCursor.TokenType tokentype = xmlcursor.toNextToken();
if (tokentype.isStart()) {
if (xmlcursor.getObject() instanceof CTR) {
CTR cTR = (CTR) xmlcursor.getObject();
cTR.addNewRPr2().addNewRFonts().setAscii("Cambria Math");
cTR.getRPr2().getRFonts().setHAnsi("Cambria Math"); // up to apache poi 4.1.2
//cTR.getRPr2().getRFontsArray(0).setHAnsi("Cambria Math"); // since apache poi 5.0.0
}
}
}
return ctOMath;
}
已发现无法识别的符号（目前没有找到解决方案）
尝试了很多中组件，spire.doc 、fmath 等都无法渲染 extcircled ,这个是latex标准支持的公式，效果文本外面圈一个圈类似①这样的效果，这里尝试无果之后只能暂时以比较恶心的方式解决这个问题，方法latexFilter，我这里只有①②③④这个四个出现的比较多，其他的都没有出现，如果要使用这个地方需要注意一下
private static String latexFilter(String latex){
if(!latex.contains("textcircled")){
return latex;
}
return TextCircledEnum.replaceTextCircled(latex);
}
private enum TextCircledEnum{
Zero("\\textcircled\{0\}","⓪"),
One("\\textcircled\{1\}","①"),
Two("\\textcircled\{2\}","②"),
Three("\\textcircled\{3\}","③"),
Four("\\textcircled\{4\}","④"),
Five("\\textcircled\{5\}","⑤"),
Six("\\textcircled\{6\}","⑥"),
Seven("\\textcircled\{7\}","⑦"),
Eight("\\textcircled\{8\}","⑧"),
Nine("\\textcircled\{9\}","⑨"),
Ten("\\textcircled\{10\}","⑩")
;
TextCircledEnum(String code, String v) {
this.code = code;
this.v = v;
}
public final String code;
public final String v;
public static String replaceTextCircled(String latex){
for (TextCircledEnum c : TextCircledEnum.values()) {
latex = latex.replaceAll(c.code,c.v);
}
return latex;
}
}
测试代码，附带大量latex公式
public static void main(String[] args) throws Exception {
XWPFDocument document = new XWPFDocument();
XWPFParagraph paragraph = document.createParagraph();
paragraph.setAlignment(ParagraphAlignment.LEFT);
List<String> latexList = Arrays.asList("$\frac{\sum\limits_{i=1}^{n}({x}_{i}−\overline{x})({y}_{i}−\overline{y})}{\sum\limits_{i=1}^{n}({x}_{i}−\overline{x}{)}^{2}}$"
, "$\frac{ \sum _{i=1}^{n} (x_ {i}-\overline {x})(y_ {i}-\overline {y})}{\sqrt { \sum _{i=1}^{n} (x_ {i-x})^ {2} \sum _{i=1}^{n} (y_ {i}-y)^ {2}}}$"
, "$\widehat{y}$"
, "$s_{x}^ {2}$"
, "$\sum _{i=1}^{n}$"
, "$\frac%…7B(a+b)(c+d)(a+c)(b+d)}$"
, "$0 \geqslant x\leqslant 5 \widehat{A} \hat{A} \sideset{^1_2}{^3_4}Y \sideset{^1_2}{^3_4}Y $"
, "$\textcircled{1}$"
, "$\textcircled1$"
, "$\f\relax{x} = \int_{-\infty}^\infty \f\hat\xi\,e^{2 \pi i \xi x} \,d\xi$"
, "$a_{1} \quad x^2 \quad e^{- \alpha t} \quad b^{3}_{ij} \quad e^{2}\neq {e^x}^2$"
, "$\sqrt{x} \quad \sqrt[3]{x} \quad \sqrt{x^{2}+ \sqrt{y}}$"
, "$\frac{x^2}{k+1} \quad x^{\frac{2}{k+1}} \quad x^{1/2}$"
, "$\vec a \qquad \overrightarrow{AB} \qquad \overleftarrow{AB}$"
, "$\sum_{i=1}^{n} \quad \int_{0}^{\frac{\pi}{2}} \quad \prod_{\epsilon}$"
, "$\alpha \beta \gamma \sigma \omega \delta \pi \rho \epsilon \eta \lambda \mu \xi \tau \kappa \zeta \phi \chi$"
, "$\le \ge \ne \approx \sim \subseteq \in \notin \times \div \pm \Rightarrow \rightarrow \infty \partial \angle \triangle$"
, "$\left\{
" +
" \begin{array}{**lr**}
" +
" x=\dfrac{3\pi}{2}(1+2t)\cos(\dfrac{3\pi}{2}(1+2t)), & \\
" +
" y=s, & 0\leq s\leq L,|t|\leq1.\\
" +
" z=\dfrac{3\pi}{2}(1+2t)\sin(\dfrac{3\pi}{2}(1+2t)), &
" +
" \end{array}
" +
"\right.
$"
,"$F^{HLLC}=\left\{
" +
"\begin{array}{rcl}
" +
"F_L & & {0 < S_L}\\
" +
"F^*_L & & {S_L \leq 0 < S_M}\\
" +
"F^*_R & & {S_M \leq 0 < S_R}\\
" +
"F_R & & {S_R \leq 0}
" +
"\end{array} \right. $"
,"$\Bigg ( \bigg [ \Big \{\big \langle \left \vert \parallel \frac{a}{b} \parallel \right \vert \big \rangle \Big \} \bigg ] \Bigg )$"
);
latexList.forEach(latex -> addLatex(latexFilter(latex), document.createParagraph()));
FileOutputStream out = new FileOutputStream("CreateWordFormulaFromMathML.docx");
document.write(out);
out.close();
document.close();
}
fmath转换Latex为MathML（弃用）
上面的公式用fmath三件套的转换的时候有报错地方，而且转换后的效果有不及预期的，所以就弃用了，下面是fmath转换的代码
@SneakyThrows
public static void addLatexByFMath(String latex, XWPFParagraph paragraph) {
String mathML = fmath.conversion.ConvertFromLatexToMathML.convertToMathML(latex);
mathML = mathML.replaceFirst("<math ", "<math xmlns="http://www.w3.org/1998/Math/MathML" ");
mathML = mathML.replaceAll("±", "±");
CTOMath ctOMath = getOMML(mathML);
CTP ctp = paragraph.getCTP();
CTOMath ctoMath = ctp.addNewOMath();
ctoMath.set(ctOMath);
}
POI生成Word代码API介绍
生成段落
private XWPFParagraph newParagraph(XWPFDocument document) {
XWPFParagraph paragraph = document.createParagraph();
paragraph.setSpacingLineRule(LineSpacingRule.AUTO);
paragraph.setSpacingBefore(30);
paragraph.setAlignment(ParagraphAlignment.LEFT);
return paragraph;
}
添加文字
注：POI不支持
xwpfRun.addBreak() 来实现换行
public void addText(String text, XWPFParagraph paragraph) {
if (StringUtils.isEmpty(text)) {
return;
}
XWPFRun xwpfRun = paragraph.createRun();
String[] lines = text.split("
");
if (lines.length < 1) {
return;
}
xwpfRun.setText(lines[0], 0);
for (int m = 1; m < lines.length; m++) {
xwpfRun.addBreak();
xwpfRun.setText(lines[m]);
}
if (text.endsWith("
")) {
xwpfRun.addBreak();
}
}
Table渲染
注：这里在渲染的时候把table行数和列数全部都已计算好（这个不涉及单元格合并功能），table.setWidth() 也是POI4.X版本才支持传入字符串设置百分比
private void parse2Table(WordInnerPojo innerPojo, XWPFParagraph paragraph) {
XWPFTable table = paragraph.getDocument().createTable(innerPojo.rows, innerPojo.lines);
table.setWidth("100%");
for (int i = 0; i < innerPojo.rowLines.size(); i++) {
List<String> rowLine = innerPojo.rowLines.get(i);
for (int j = 0; j < rowLine.size(); j++) {
XWPFTableCell cell = table.getRow(i).getCell(j);
XWPFParagraph innerParagraph = cell.getParagraphs().size() > 0 ? cell.getParagraphs().get(0) : cell.addParagraph();
innerParagraph.setSpacingBefore(0);
innerParagraph.setVerticalAlignment(TextAlignment.CENTER);
innerParagraph.setAlignment(ParagraphAlignment.LEFT);
addContent(rowLine.get(j), innerParagraph);
}
}
paragraph.getDocument().createParagraph();
}
插入图片
注：单位需要转换为em，直接调用org.apache.poi.util.Units的toEMU方法即可，这样的写法直接在文本的后面增加图片，不换行
paragraph.createRun().addPicture(new ByteArrayInputStream(innerPojo.image),
XWPFDocument.PICTURE_TYPE_JPEG, "",
Units.toEMU(width.intValue()),
Units.toEMU(height.intValue()));
word公式渲染POJO类和渲染逻辑
一段原始的html文本需要分段解析的，文本、公式、表格、图片等，需要解析抽象生成一个POJO类，把这些非文本的类型提出来并标记好占位符，用于替换和渲染
POJO类
private static class WordInnerPojo {
protected static final int LATEX_TYPE = 0;
protected static final int IMG_TYPE = 1;
protected static final int TABLE_TYPE = 2;
private int type;
private byte[] image;
private String latex;
private String imageUrl;
private int rows;
private int lines;
private List<List<String>> rowLines;
private BufferedImage imageTemp;
@SneakyThrows
BufferedImage readImage() {
if (this.imageTemp == null) {
this.imageTemp = ImageIO.read(new ByteArrayInputStream(this.image));
}
return imageTemp;
}
private Integer getImageWidth() {
return readImage().getWidth();
}
private Integer getImageHeight() {
return readImage().getHeight();
}
}
渲染逻辑
@SneakyThrows
private void appendWordInnerPojo(WordInnerPojo innerPojo, XWPFParagraph paragraph) {
switch (innerPojo.type) {
case WordInnerPojo.LATEX_TYPE:
addLatex(latexFilter(MessageFormat.format("${0}$", URLDecoder.decode(innerPojo.latex, "UTF-8")))), paragraph);
break;
case WordInnerPojo.IMG_TYPE:
log.info("imageUrl:{}", innerPojo.imageUrl);
/* 控制word中的图片渲染大小，不要太大 */
Float width = Float.valueOf(innerPojo.getImageWidth());
Float height = Float.valueOf(innerPojo.getImageHeight());
if (width > 300 && width > height) {
BigDecimal rate = BigDecimal.valueOf(300).divide(BigDecimal.valueOf(width), 8, BigDecimal.ROUND_DOWN);
height = height * rate.floatValue();
width = 300f;
} else if (height > 200 && height > width) {
BigDecimal rate = BigDecimal.valueOf(200).divide(BigDecimal.valueOf(height), 8, BigDecimal.ROUND_DOWN);
width = width * rate.floatValue();
height = 200f;
}
paragraph.createRun().addPicture(new ByteArrayInputStream(innerPojo.image), XWPFDocument.PICTURE_TYPE_JPEG, "", Units.toEMU(width.intValue()), Units.toEMU(height.intValue()));
paragraph.createRun().addBreak();
break;
case WordInnerPojo.TABLE_TYPE:
parse2Table(innerPojo, paragraph);
break;
}
}
搞定！导出的部分样例如下：
参考链接
https://stackoverflow.com/questions/46623554/add-latex-type-equation-in-word-docx-using-apache-poi
