按矩形获取图像

Question

我有这个方法可以提取pdf中特定位置的文本

public static void getTextByRectangle(PDDocument doc,Rectangle rect) throws IOException{
    PDFTextStripperByArea stripper = new PDFTextStripperByArea();
    stripper.setSortByPosition( true );
    stripper.addRegion( "class1", rect );
    PDPage firstPage = doc.getPage(0);
    stripper.extractRegions( firstPage );
    System.out.println( "Text in the area:" + rect );
    System.out.println( stripper.getTextForRegion( "class1" ) );
}

除了提取图像之外，是否可以做同样的事情？

Answer 1

是的，您可以提取所有图像，并比较 rect 和 images 的位置。这是pdfbox 的示例。这可以获得图像位置。

1. 你需要创建一个类扩展PDFStreamEngine。像这样，

   public class PrintImageLocations extends PDFStreamEngine

2. 您应该覆盖processOperator。而从ctmNew，你可以得到图片的位置，然后将image与你的rect进行比较，你会得到正确的图片。

   @Override
   protected void processOperator(Operator operator, List<COSBase> operands)  throws IOException {
       String operation = operator.getName();
       if ("Do".equals(operation)) {
           COSName objectName = (COSName) operands.get(0);
           PDXObject xobject = getResources().getXObject(objectName);
           if (xobject instanceof PDImageXObject) {
                PDImageXObject image = (PDImageXObject) xobject;
                Matrix ctmNew = getGraphicsState().getCurrentTransformationMatrix();
                float imageXScale = ctmNew.getScalingFactorX();
                float imageYScale = ctmNew.getScalingFactorY();
                // position in user space units. 1 unit = 1/72 inch at 72 dpi
                System.out.println("position in PDF = " + ctmNew.getTranslateX() + ", " + ctmNew.getTranslateY() + " in user space units");
                // displayed size in user space units
                System.out.println("displayed size  = " + imageXScale + ", " + imageYScale + " in user space units");
           } else if (xobject instanceof PDFormXObject) {
                PDFormXObject form = (PDFormXObject) xobject;
                showForm(form);
           }
       } else {
           super.processOperator(operator, operands);
       }
   }
   

感谢 mkl 和 FiReTiTi 的建议。