import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public void put(COSObject indirect, PDXObject xobject) throws IOException {
    final int length = xobject.getStream().getLength();
    if (length > Environment.getMaxImageSize()) {
        LOG.trace("Not caching image with Size: {}", length);
        return;
    }
    if (xobject instanceof PDImageXObject) {
        PDImageXObject imageObj = (PDImageXObject) xobject;
        if (imageObj.getWidth() * imageObj.getHeight() > Environment.getMaxImageSize()) {
            return;
        }
    }
    this.xobjects.put(indirect, new SoftReference(xobject));
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
/**
 * Processes the operators of the given content stream.
 * 
 * @param stream
 *          the stream.
 * @throws IOException
 *           if parsing the stream fails.
 */
protected void processStreamOperators(PDContentStream stream)
  throws IOException {
  List<COSBase> arguments = new ArrayList<COSBase>();
  PDFStreamParser parser = new PDFStreamParser(stream);
  
  parser.parse();
  for (Object token : parser.getTokens()) {
    if (token instanceof COSObject) {
      arguments.add(((COSObject) token).getObject());
    } else if (token instanceof Operator) {
      processOperator((Operator) token, arguments);
      arguments = new ArrayList<COSBase>();
    } else {
      arguments.add((COSBase) token);
    }
  }
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDXObject getXObject(COSObject indirect) throws IOException {
    SoftReference<PDXObject> xobject = this.xobjects.get(indirect);
    if (xobject != null) {
        return xobject.get();
    }
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDShading getShading(final COSObject indirect) throws IOException {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
protected boolean removeEldestEntry(final Entry<COSObject, SoftReference<PDXObject>> eldest) {
    return size() > Environment.getNrOfImagesToCache();
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDFont getFont(final COSObject indirect) throws IOException {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDColorSpace getColorSpace(final COSObject indirect) throws IOException {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDExtendedGraphicsState getExtGState(final COSObject indirect) {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDAbstractPattern getPattern(final COSObject indirect) throws IOException {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDPropertyList getProperties(final COSObject indirect) {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public PDXObject getXObject(final COSObject indirect) throws IOException {
    return null;
}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
@Override
public void put(final COSObject indirect, final PDFont font) throws IOException {}
 

import org.apache.pdfbox.cos.COSObject; //导入依赖的package包/类
void removeToUnicodeMaps(PDResources pdResources) throws IOException
{
    COSDictionary resources = pdResources.getCOSObject();

    COSDictionary fonts = asDictionary(resources, COSName.FONT);
    if (fonts != null)
    {
        for (COSBase object : fonts.getValues())
        {
            while (object instanceof COSObject)
                object = ((COSObject)object).getObject();
            if (object instanceof COSDictionary)
            {
                COSDictionary font = (COSDictionary)object;
                font.removeItem(COSName.TO_UNICODE);
            }
        }
    }

    for (COSName name : pdResources.getXObjectNames())
    {
        PDXObject xobject = pdResources.getXObject(name);
        if (xobject instanceof PDFormXObject)
        {
            PDResources xobjectPdResources = ((PDFormXObject)xobject).getResources();
            removeToUnicodeMaps(xobjectPdResources);
        }
    }
}