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我正在嘗試開發支持i18n和多行水印的水印壓印。我可以創建它，但問題是水印與前一行的文本重疊，如下圖所示。 
多行水印重疊問題
我的水印文本包含以下內容：123\n456\n789。我願意做的就是在不重疊線條的情況下設置水印。我怎樣才能做到這一點？下面是我的代碼部分：
WaterMarkStamper.java
public void insertWaterMark() throws Exception {
final File pdfFile = this.getFile();
if (pdfFile != null && pdfFile.exists()) {
PdfReader reader = null;
PdfStamper stamp = null;
try {
reader = new PdfReader(pdfFile.getAbsolutePath());
final int n = reader.getNumberOfPages();
temp = this.getNewFile();
// Create a stamper that will copy the document to a new file
stamp = new PdfStamper(reader, new FileOutputStream(temp));
PdfContentByte over;
int pageIndex = 1;
while (pageIndex <= n) {
over = stamp.getOverContent(pageIndex);
this.addWatermark(wmVO, reader, over, pageIndex, position);
pageIndex++;
}
} catch (final Exception e) {
WaterMarkStamper.logger.error(e.getMessage(), e);
} finally {
if (stamp != null) {
stamp.close();
}
if (reader != null) {
reader.close();
}
}
}
}
private void addWatermark(final WaterMarkVO wmVo, final PdfReader reader, final PdfContentByte contentByte, final Integer pageIndex) throws Exception {
final Rectangle page = reader.getPageSizeWithRotation(pageIndex);
// This is where the magic happens
final Image img = wmVo.getImage(contentByte);
// Get margins
final int leftMargin = wmVo.getLeftMargin();
final int topMargin = wmVo.getTopMargin();
final int rightMargin = wmVo.getRightMargin();
final int bottomMargin = wmVo.getBottomMargin();
// Absolute position
final Point pt = this.getImageInsertionPoint(img, page, leftMargin, topMargin, rightMargin, bottomMargin);
img.setAbsolutePosition((float) pt.getX(), (float) pt.getY());
// Add image
contentByte.addImage(img);
}
WaterMarkVO.java
public Image getImage(final PdfContentByte contentByte) throws Exception {
final Paragraph paragraph = this.getParagraph();
final Rectangle paragraphRectangle = this.getParagraphRectangle();
final float paragraphHeight = paragraphRectangle.getHeight();
final float paragraphWidth = paragraphRectangle.getWidth();
final PdfTemplate xObject = contentByte.createTemplate(paragraphWidth, paragraphHeight + this.getFontSize());
final ColumnText column = new ColumnText(xObject);
column.setSimpleColumn(0, 0, paragraphWidth, paragraphHeight);
column.setExtraParagraphSpace(0f);
column.addElement(paragraph);
column.go();
final Image img = Image.getInstance(xObject);
final int rotation = this.getRotation();
img.setRotationDegrees(rotation);
return img;
}
public Paragraph getParagraph() throws Exception {
final FontSelector fontSelector = this.getFontSelector();
final String text = "123\n456\n789";
this.fontSelectorPhrase = fontSelector.process(text);
final Paragraph paragraph = new Paragraph(this.fontSelectorPhrase);
return paragraph;
}
public Rectangle getParagraphRectangle() throws Exception {
final String text = "123\n456\n789";
final float fontSize = this.getFontSize();
float paragraphWidth = 0f;
float paragraphHeight = 0f;
float leading = 0f;
final String[] lines = text.split("\n");
List<Chunk> chunks = this.fontSelectorPhrase.getChunks();
for(Chunk c : chunks) {
int indexer = 0;
final Paragraph p = new Paragraph(" ", c.getFont());
do {
final float currentLineWidth = c.getFont().getBaseFont().getWidthPoint(" " + lines[indexer] + " ", fontSize);
final float currentLineHeight = c.getFont().getBaseFont().getAscentPoint(lines[indexer], fontSize) + c.getFont().getBaseFont().getDescentPoint(lines[indexer], fontSize);
final float curentLineLeading = p.getLeading();
paragraphWidth = currentLineWidth > paragraphWidth ? currentLineWidth : paragraphWidth;
paragraphHeight = currentLineHeight > paragraphHeight ? currentLineHeight : paragraphHeight;
leading = currentLineLeading > leading ? currentLineLeading : leading;
indexer++;
} while (indexer < lines.length);
}
paragraphHeight += leading/lines.length;
return new Rectangle(paragraphWidth, paragraphHeight);
}
public FontSelector getFontSelector() throws Exception {
// Adding fonts to support i18n
FontSelector fontSelector = new FontSelector();
fontSelector.addFont(new Font(BaseFont.createFont(BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED))); // Does not support some turkish glyphs
fontSelector.addFont(new Font(BaseFont.createFont("helvetica.ttf", BaseFont.IDENTITY_H, BaseFont.EMBEDDED))); // Support some turkish glyphs
return fontSelector;
}
很顯然，我一直認爲是不必要的代碼隱藏的部分。在這個例子中，我沒有在水印上使用特殊字符，但是我的代碼必須遵守這個要求（我遵循在「iText in Action 2nd edition」中的p378中所述）。