java - 文本居中，不考虑 x 坐标

Question

我修改了 TextToPDF 类来检测内容文件中的某些标签。当找到标签中心时，文本居中。

这不能正常工作，X 坐标似乎不受尊重

当我显示 x: 坐标时，我得到:0

0

18.861816

2.9138184

238.31181

9.933823

68.68582

10.347824

40.14981

在生成的 pdf 中，第 6 行应该在第 5 行之前开始，但它在第 5 行之后开始。

238.31181 > 9.933823 但 pdfbox 似乎说 9.933823 > 238.31181

生成文件的结果

该字符串被放入 createPDFFromText 参数的 StringReader 中。

String rawText = "Children's heart surgery has been suspended with immediate effect at a hospital which is embroiled in a long-running row over the future of paediatric cardiac services in England. \n "
    + "#CENTER#The decision to stop congenital heart surgery at Leeds General Infirmary comes just a day after the High Court quashed plans by the NHS to close its children's unit after ruling the consultation process was flawed.\n "
    + "It follows concerns raised about patients' care including allegations the hospital was avoiding referring children for complex and life-saving treatment at another centre in Newcastle.\n "
    + "Leeds Teaching Hospitals NHS Trust said the temporary measure was being taken to allow an internal review to be conducted following consultation with the Care Quality Commission (CQC).";

代码

public PDDocument createPDFFromText( Reader text ) throws IOException
{
    PDDocument doc = null;
    PDSimpleFont font = PDType1Font.TIMES_ROMAN;
    int fontSize = 12;
    boolean isCentered = false;
    try
    {

        final int margin = 40;
        float height = font.getFontDescriptor().getFontBoundingBox().getHeight()/1000;

        //calculate font height and increase by 5 percent.
        height = height*fontSize*1.05f;
        doc = new PDDocument();
        BufferedReader data = new BufferedReader( text );
        String nextLine = null;
        PDPage page = new PDPage();
        PDPageContentStream contentStream = null;
        float y = -1;
        float maxStringLength = page.getMediaBox().getWidth() - 2*margin;

        // There is a special case of creating a PDF document from an empty string.
        boolean textIsEmpty = true;

        while( (nextLine = data.readLine()) != null )
        {

            // The input text is nonEmpty. New pages will be created and added
            // to the PDF document as they are needed, depending on the length of
            // the text.
            textIsEmpty = false;

            String[] lineWords = nextLine.trim().split( " " );
            int lineIndex = 0;
            while( lineIndex < lineWords.length )
            {
                StringBuffer nextLineToDraw = new StringBuffer();
                float lengthIfUsingNextWord = 0;
                do
                {
                    nextLineToDraw.append( lineWords[lineIndex] );
                    nextLineToDraw.append( " " );
                    lineIndex++;
                    if( lineIndex < lineWords.length )
                    {
                        String lineWithNextWord = nextLineToDraw.toString() + lineWords[lineIndex];
                        lengthIfUsingNextWord =
                            (font.getStringWidth( lineWithNextWord )/1000) * fontSize;
                    }
                }
                while( lineIndex < lineWords.length &&
                       lengthIfUsingNextWord < maxStringLength );
                if( y < margin )
                {
                    // We have crossed the end-of-page boundary and need to extend the
                    // document by another page.
                    page = new PDPage();
                    doc.addPage( page );
                    if( contentStream != null )
                    {
                        contentStream.endText();
                        contentStream.close();
                    }
                    contentStream = new PDPageContentStream(doc, page);
                    contentStream.setFont( font, fontSize );
                    contentStream.beginText();
                    y = page.getMediaBox().getHeight() - margin + height;
                    contentStream.moveTextPositionByAmount(
                        margin, y );

                }
                //System.out.println( "Drawing string at " + x + "," + y );

                if( contentStream == null )
                {
                    throw new IOException( "Error:Expected non-null content stream." );
                }

                String txt = nextLineToDraw.toString();

                if ( txt.indexOf( "#CENTER#" ) != -1 || isCentered )
                {
                    txt = nextLineToDraw.toString().replaceAll( "#CENTER#", "" );

                    PDRectangle pageSize = page.findMediaBox();
                    float stringWidth = font.getStringWidth( txt );
                    float xPosition = ( pageSize.getWidth() - ( 2 * margin ) - ( stringWidth * fontSize ) / 1000f ) / 2f;

                    System.out.println( xPosition );

                    contentStream.moveTextPositionByAmount( xPosition, -height );
                    isCentered = true;
                }
                else
                {
                                            System.out.println( 0);
                    contentStream.moveTextPositionByAmount( 0, -height );
                }

                y -= height;
                contentStream.drawString( nextLineToDraw.toString() );
            }
        }
        if (textIsEmpty)
        {
            doc.addPage(page);
        }

        if( contentStream != null )
        {
            contentStream.endText();
            contentStream.close();
        }
    }
    catch( IOException io )
    {
        if( doc != null )
        {
            doc.close();
        }
        throw io;
    }
    return doc;
}

文件结果可在此处获取:http://filebin.ca/br6slMSfOR6/testUnitairePdf.pdf正如您所看到的，文本未正确居中。

Answer 1

问题是(就像 @GaborSch 在他对答案的评论中猜测的那样)

contentStream.moveTextPositionByAmount()

相对于最后一行，而不是相对于某个固定边距。

详细信息:

PDPageContentStream 方法 moveTextPositionByAmount 记录为:

/**
 * The Td operator.
 * @param x The x coordinate.
 * @param y The y coordinate.
 * @throws IOException If there is an error writing to the stream.
 */
public void moveTextPositionByAmount( float x, float y ) throws IOException

Td 运算符又记录为:

tx ty Td Move to the start of the next line, offset from the start of the current line by (tx, ty). tx and ty shall denote numbers expressed in unscaled text space units. More precisely, this operator shall perform these assignments:

(参见 PDF 规范 ISO 32000-1:2008，第 9.4.2 节“文本定位运算符”)

因此，您必须记住使用的 xPosition 值，并且

• 紧接该行之后

  contentStream.drawString( nextLineToDraw.toString() );
  

  插入

  contentStream.moveTextPositionByAmount( -xPosition, 0 );
  

  如果线居中；

• 或者等到确定下一行文本的 moveTextPositionByAmount 参数，然后从新的 x 值中减去之前的 xPosition 值。