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java - 使用 iText7 在高亮注释上设置外观流

问题描述

我有一个 PDF 查看器，如果它们没有外观流，则不会显示亮点。我正在java中尝试iText 7核心来尝试向PDF添加高亮注释，但这些注释没有外观流，因此我希望在将注释写入PDF文件时尝试自己添加它们。

我遇到了这个旧答案，但它适用于 C# 和 iText 5，我似乎无法弄清楚如何在 iText 7 中成功复制它。

所以我的问题是：如何在 iText 7 核心中的突出显示注释上设置外观流？

我得到的最远的代码如下所示。我正在使用 RegexBasedLocationExtrationStrategy 类来查找 pdf 中所有搜索词的位置。

RegexBasedLocationExtractionStrategy evntlstnr = new RegexBasedLocationExtractionStrategy(pattern);
for (int pIdx = 0; pIdx < pdfDoc.getNumberOfPages(); ++pIdx) {
    final PdfPage page = pdfDoc.getPage(pIdx + 1);
    new PdfCanvasProcessor(evntlstnr).processPageContent(page);
    Collection<IPdfTextLocation> locations =  evntlstnr.getResultantLocations();
    for (IPdfTextLocation location : locations) {
        Rectangle rect = location.getRectangle();
        // Specify quad points in Z-like order
        // [0,1] x1,y1   [2,3] x2,y2
        // [4,5] x3,y3   [6,7] x4,y4
        float[] quads = new float[8];
        quads[0] = rect.getX();
        quads[1] = rect.getY() + rect.getHeight();
        quads[2] = rect.getX() + rect.getWidth();
        quads[3] = quads[1];
        quads[4] = quads[0];
        quads[5] = rect.getY();
        quads[6] = quads[2];
        quads[7] = quads[5];

        Color highlightColor = new DeviceRgb(0f, 0f, 1f);
        PdfTextMarkupAnnotation highlight = PdfTextMarkupAnnotation.createHighLight(rect, quads);
        highlight.setColor(highlightColor);


        Rectangle appearRect = new Rectangle(0f, 0f, rect.getWidth(), rect.getHeight());                            
        PdfFormXObject appearObj = new PdfFormXObject(appearRect);                                                        
        final PdfResources appearRes = appearObj.getResources();

        PdfExtGState extGState = new PdfExtGState();
        extGState.setBlendMode(PdfExtGState.BM_MULTIPLY);
        appearRes.addExtGState(extGState);
        appearObj.setBBox(new PdfArray(new float[] {0f, 0f, rect.getWidth(), rect.getHeight()}));

        PdfShading appearShading = new PdfShading.Axial(highlightColor.getColorSpace(), 0f, 0f, highlightColor.getColorValue(), 1f, 1f, highlightColor.getColorValue());                                                     
        appearRes.addShading(appearShading);

        appearRes.addColorSpace(highlightColor.getColorSpace());                            

        PdfAnnotationAppearance appearance = new PdfAnnotationAppearance(appearObj.getPdfObject());
        highlight.setNormalAppearance(appearance);
        highlight.setFlag(PdfAnnotation.PRINT);
        page.addAnnotation(highlight);
    }
}

标签： javaannotationshighlightitext7appearance

解决方案

使用塞缪尔的答案，我偶然发现了一个可行的答案。

我对 PDF 标准和这个框架（iText）没有任何期望，但我的假设是，基于我下面的工作示例，我试图为突出显示编写的矩形是“伪造”的粗略后备方法当查看器无法呈现注释时的高亮矩形（因为它们没有外观流）。意识到这两个操作没有关联，我来到了下面显示的工作示例。希望这对将来的其他人有所帮助。

RegexBasedLocationExtractionStrategy evntlstnr = new RegexBasedLocationExtractionStrategy(pattern);
for (int pIdx = 0; pIdx < pdfDoc.getNumberOfPages(); ++pIdx) {
    final PdfPage page = pdfDoc.getPage(pIdx + 1);
    new PdfCanvasProcessor(evntlstnr).processPageContent(page);
    Collection<IPdfTextLocation> locations =  evntlstnr.getResultantLocations();
    for (IPdfTextLocation location : locations) {
        Rectangle rect = location.getRectangle();
        // Specify quad points in Z-like order
        // [0,1] x1,y1   [2,3] x2,y2
        // [4,5] x3,y3   [6,7] x4,y4
        float[] quads = new float[8];
        quads[0] = rect.getX();
        quads[1] = rect.getY() + rect.getHeight();
        quads[2] = rect.getX() + rect.getWidth();
        quads[3] = quads[1];
        quads[4] = quads[0];
        quads[5] = rect.getY();
        quads[6] = quads[2];
        quads[7] = quads[5];

        Color highlightColor = new DeviceRgb(1f, 1f, 0f);                                                                                                                           

        PdfTextMarkupAnnotation highlight = PdfTextMarkupAnnotation.createHighLight(rect, quads);
        highlight.setColor(highlightColor); 
        highlight.setFlag(PdfAnnotation.PRINT);
        page.addAnnotation(highlight);                            

        PdfCanvas canvas = new PdfCanvas(page);
        PdfExtGState extGState = new PdfExtGState();
        extGState.setBlendMode(PdfExtGState.BM_MULTIPLY);
        canvas.setExtGState(extGState);
        canvas.rectangle(rect.getX(), rect.getY(), rect.getWidth(), rect.getHeight());
        canvas.setFillColor(highlightColor);
        canvas.fill();                            
        canvas.release();                                                        
    }
}

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