假设我成功地将 PDTerminalField 转换为 PDPushButton 的实例。 但查看提供的 API,我无法猜测如何提取所述按钮的标签。
由于应用程序过于冗长,因此未添加代码。 这是示例pdf .
最佳答案
(感谢@Tilman在这里纠正我。)确实有这样一个属性,你可以通过getAppearanceCharacteristics().getNormalCaption()
访问它,但是这个属性是可选的,并且不能保证其内容与按钮的视觉外观一致,因为外观流可能包含不同的信息。因此,可能需要查询属性和读取外观流的组合策略。
PDF 中按钮的外观流可以包含任意数量的图形和文本绘制指令来绘制按钮,但该流不一定易于阅读或解析。例如。对于 OP 提供的示例文件,该流如下所示:
1 0.75 0.666656 rg
0 0 72 20 re
f
q
1 1 70 18 re
W
n
0 g
BT
/HeBo 12 Tf
0 g
6.696 5.857 Td
(My ) Tj
19.992 0 Td
(Button) Tj
ET
Q
这里已经可以看到按钮文本“My Button”,但显然必须进行一些解析才能检索它(特别是因为文本编码不需要像在本例中那样从 ASCII 派生),一必须将文本提取应用于流。
不幸的是,PDFBox 中的主要文本提取工具,即 PdfTextStripper
类,很难应用于除页面内容之外的任何其他内容。因此,我使用文本剥离器派生的基类,仅添加最少的文本排列功能,并将其应用到按钮外观流。
import java.io.IOException;
import org.apache.pdfbox.contentstream.PDFStreamEngine;
import org.apache.pdfbox.contentstream.operator.DrawObject;
import org.apache.pdfbox.contentstream.operator.state.Concatenate;
import org.apache.pdfbox.contentstream.operator.state.Restore;
import org.apache.pdfbox.contentstream.operator.state.Save;
import org.apache.pdfbox.contentstream.operator.state.SetGraphicsStateParameters;
import org.apache.pdfbox.contentstream.operator.state.SetMatrix;
import org.apache.pdfbox.contentstream.operator.text.BeginText;
import org.apache.pdfbox.contentstream.operator.text.EndText;
import org.apache.pdfbox.contentstream.operator.text.MoveText;
import org.apache.pdfbox.contentstream.operator.text.MoveTextSetLeading;
import org.apache.pdfbox.contentstream.operator.text.NextLine;
import org.apache.pdfbox.contentstream.operator.text.SetCharSpacing;
import org.apache.pdfbox.contentstream.operator.text.SetFontAndSize;
import org.apache.pdfbox.contentstream.operator.text.SetTextHorizontalScaling;
import org.apache.pdfbox.contentstream.operator.text.SetTextLeading;
import org.apache.pdfbox.contentstream.operator.text.SetTextRenderingMode;
import org.apache.pdfbox.contentstream.operator.text.SetTextRise;
import org.apache.pdfbox.contentstream.operator.text.SetWordSpacing;
import org.apache.pdfbox.contentstream.operator.text.ShowText;
import org.apache.pdfbox.contentstream.operator.text.ShowTextAdjusted;
import org.apache.pdfbox.contentstream.operator.text.ShowTextLine;
import org.apache.pdfbox.contentstream.operator.text.ShowTextLineAndSpace;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;
import org.apache.pdfbox.util.Matrix;
import org.apache.pdfbox.util.Vector;
public class SimpleXObjectTextStripper extends PDFStreamEngine {
public SimpleXObjectTextStripper() {
addOperator(new BeginText());
addOperator(new Concatenate());
addOperator(new DrawObject()); // special text version
addOperator(new EndText());
addOperator(new SetGraphicsStateParameters());
addOperator(new Save());
addOperator(new Restore());
addOperator(new NextLine());
addOperator(new SetCharSpacing());
addOperator(new MoveText());
addOperator(new MoveTextSetLeading());
addOperator(new SetFontAndSize());
addOperator(new ShowText());
addOperator(new ShowTextAdjusted());
addOperator(new SetTextLeading());
addOperator(new SetMatrix());
addOperator(new SetTextRenderingMode());
addOperator(new SetTextRise());
addOperator(new SetWordSpacing());
addOperator(new SetTextHorizontalScaling());
addOperator(new ShowTextLine());
addOperator(new ShowTextLineAndSpace());
}
public String getText(PDFormXObject form) throws IOException {
stringBuilder.setLength(0);
processChildStream(form, new PDPage());
return stringBuilder.toString();
}
@Override
protected void showGlyph(Matrix textRenderingMatrix, PDFont font, int code, String unicode, Vector displacement)
throws IOException {
stringBuilder.append(unicode);
}
final StringBuilder stringBuilder = new StringBuilder();
}
(我包含了 import
语句,因为 PDFBox 在此包含几个名称相似的类。)
使用这个简单的自定义剥离器类,可以从字段外观中提取文本内容,如下所示:
public void showNormalFieldAppearanceTexts(PDDocument document) throws IOException {
PDAcroForm acroForm = document.getDocumentCatalog().getAcroForm();
if (acroForm != null) {
SimpleXObjectTextStripper stripper = new SimpleXObjectTextStripper();
for (PDField field : acroForm.getFieldTree()) {
if (field instanceof PDTerminalField) {
PDTerminalField terminalField = (PDTerminalField) field;
System.out.println();
System.out.println("* " + terminalField.getFullyQualifiedName());
for (PDAnnotationWidget widget : terminalField.getWidgets()) {
PDAppearanceDictionary appearance = widget.getAppearance();
if (appearance != null) {
PDAppearanceEntry normal = appearance.getNormalAppearance();
if (normal != null) {
Map<COSName, PDAppearanceStream> streams = normal.isSubDictionary() ? normal.getSubDictionary() :
Collections.singletonMap(COSName.DEFAULT, normal.getAppearanceStream());
for (Map.Entry<COSName, PDAppearanceStream> entry : streams.entrySet()) {
String text = stripper.getText(entry.getValue());
System.out.printf(" * %s: %s\n", entry.getKey().getName(), text);
}
}
}
}
}
}
}
}
(ExtractAppearanceText辅助方法)
关于java - 如何使用 Apache PDFBox 从按钮中提取标签文本?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49427615/