如何使用ITextSharp读取线宽注释的外观？

Question

//main function for setting inner content to appearance value
public void changeAnnotationContentToAppearance(PdfDictionary dict)
        {

                string surface = pdfTextParser.retrieveText(dict);
                if (surface != null)
                {
                   //update CONTENTS with appearance
                   //for changing line width, I would instead modify the /BS dictionary's /W key value, i think
                   dict.Put(PdfName.CONTENTS, new PdfString(surface));
                }
        }

//get text from /AP dictionary
public string retrieveText(PdfDictionary annotDictionary)
    {

        PdfDictionary appearancesDictionary = annotDictionary.GetAsDict(PdfName.AP);
        foreach (PdfName key in appearancesDictionary.Keys)
        {
            PdfStream value = appearancesDictionary.GetAsStream(key);
            if (value != null)
            {
                String text = ExtractAnnotationText(value);
                return text;
            }
        }
        return null;

    }

//read the appearance stream and extract text contents
public String ExtractAnnotationText(PdfStream xObject)
{
    PdfDictionary resources = xObject.GetAsDict(PdfName.RESOURCES);
    ITextExtractionStrategy strategy = new LocationTextExtractionStrategy();

    PdfContentStreamProcessor processor = new PdfContentStreamProcessor(strategy);
    processor.ProcessContent(ContentByteUtils.GetContentBytesFromContentObject(xObject), resources);
    return strategy.GetResultantText();
}

如果我读对了，这个问题，这个问题，这个问题表明我需要实现一个类，但我不确定我应该用哪个子类来获取行数据，或者我应该如何去做。

编辑：我还想获得定义文本框中矩形的点的外观数据。尽管这可能是一个不同的问题，但它似乎与这个问题密切相关：检索定义注释外观流的非文本图形数据。

Answer 1

您需要PathRenderInfo对象来获取有关线条和形状的信息。在iText7中引入了PathRenderInfo对象。这是我很快写的概念证明：

public static void main(String args[]) throws IOException {
    PdfDocument document = new PdfDocument(new PdfReader(SRC));
    PdfPage page = document.getPage(1);
    PdfCanvasProcessor processor = new PdfCanvasProcessor(new IEventListener() {
        public void eventOccurred(IEventData data, EventType type) {
            if (type == EventType.RENDER_PATH) {
                PathRenderInfo renderinfo = (PathRenderInfo) data;
                int i = renderinfo.getOperation();
                switch (i) {
                    case 1:
                        System.out.print("Stroke: ");
                        break;
                    case 2:
                        System.out.print("Fill: ");
                        break;
                    default:
                        System.out.print("No: ");
                }
                for (Subpath p : renderinfo.getPath().getSubpaths()) {
                    for (IShape shape : p.getSegments()) {
                        for (Point point : shape.getBasePoints()) {
                            System.out.println(String.format("x = %s; y = %s", point.getX(), point.getY()));
                        }
                    }
                }
            }
        }
        public Set<EventType> getSupportedEvents() {
            return null;
        }
    });
    processor.processPageContent(page);
}

我在一个有很多行的PDF上运行它，这是输出的一部分：

Stroke: x = -406.0; y = -240.0
x = 406.0; y = -240.0
x = -406.0; y = -200.0
x = 406.0; y = -200.0
x = -406.0; y = -160.0
x = 406.0; y = -160.0
x = -406.0; y = -120.0
x = 406.0; y = -120.0
x = -406.0; y = -80.0
x = 406.0; y = -80.0
x = -406.0; y = -40.0
x = 406.0; y = -40.0
x = -406.0; y = 0.0
x = 406.0; y = 0.0
x = -406.0; y = 40.0
x = 406.0; y = 40.0
x = -406.0; y = 80.0

您必须升级到iText7才能完成这项工作，还必须了解PathRenderInfo、Subpath和ISHAPE对象中包含哪些信息。

外观是由查看器根据以下值创建的：

• /c:颜色：红色=0,绿色=0,蓝色=1（因此行是蓝色）
• /le:行尾（在本例中为菱形）
• L:(x=20,y=790)和(x=575,y=790)
之间的线
• ...

如果在注释字典中手头有所有必要的信息，为什么还要解析外观？