使用PDFBox从PDF获取可见签名? [英] Get Visible Signature from a PDF using PDFBox?
问题描述
是否可以通过OSS库PDFBox提取签名的PDF的可见签名(图像)?
Is it possible to extract the visible signature (image) of an signed PDF with the OSS library PDFBox?
工作流程:
- 列出文件的所有签名
- 显示哪些签名包含可见签名
- 显示哪些有效
- 提取签名图像(需要为每个签名提取正确的图像)
oop风格的东西真棒:
Something in oop style like following would be awesome:
PDFSignatures [] sigs = document.getPDFSignatures()
sig[0].getCN()
...
(Buffered)Image visibleSig = sig[0].getVisibleSignature()
创建了类PDSignature以及如何对PDF进行签名，但不是将可见签名作为图像提取的解决方案.
Found class PDSignature and how to sign a PDF, but not a solution to extract an visible signature as image.
推荐答案
由于没有人来回答，我自己在对您的问题的评论中尝试了我的提议.第一个结果:
As no one came up to answer, I tried my proposal in the comments to your question myself. A first result:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdfviewer.PageDrawer;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.graphics.PDGraphicsState;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotation;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAppearanceDictionary;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAppearanceStream;
public class AnnotationDrawer extends PageDrawer
{
public AnnotationDrawer(int imageType, int resolution) throws IOException
{
super();
this.imageType = imageType;
this.resolution = resolution;
}
public Map<String, BufferedImage> convertToImages(PDPage p) throws IOException
{
page = p;
final Map<String, BufferedImage> result = new HashMap<String, BufferedImage>();
List<PDAnnotation> annotations = page.getAnnotations();
for (PDAnnotation annotation: annotations)
{
String appearanceName = annotation.getAppearanceStream();
PDAppearanceDictionary appearDictionary = annotation.getAppearance();
if( appearDictionary != null )
{
if( appearanceName == null )
{
appearanceName = "default";
}
Map<String, PDAppearanceStream> appearanceMap = appearDictionary.getNormalAppearance();
if (appearanceMap != null)
{
PDAppearanceStream appearance =
(PDAppearanceStream)appearanceMap.get( appearanceName );
if( appearance != null )
{
BufferedImage image = initializeGraphics(annotation);
setTextMatrix(null);
setTextLineMatrix(null);
getGraphicsStack().clear();
processSubStream( page, appearance.getResources(), appearance.getStream() );
String name = annotation.getAnnotationName();
if (name == null || name.length() == 0)
{
name = annotation.getDictionary().getString(COSName.T);
if (name == null || name.length() == 0)
{
name = Long.toHexString(annotation.hashCode());
}
}
result.put(name, image);
}
}
}
}
return result;
}
BufferedImage initializeGraphics(PDAnnotation annotation)
{
PDRectangle rect = annotation.getRectangle();
float widthPt = rect.getWidth();
float heightPt = rect.getHeight();
float scaling = resolution / (float)DEFAULT_USER_SPACE_UNIT_DPI;
int widthPx = Math.round(widthPt * scaling);
int heightPx = Math.round(heightPt * scaling);
//TODO The following reduces accuracy. It should really be a Dimension2D.Float.
Dimension pageDimension = new Dimension( (int)widthPt, (int)heightPt );
BufferedImage retval = new BufferedImage( widthPx, heightPx, imageType );
Graphics2D graphics = (Graphics2D)retval.getGraphics();
graphics.setBackground( TRANSPARENT_WHITE );
graphics.clearRect( 0, 0, retval.getWidth(), retval.getHeight() );
graphics.scale( scaling, scaling );
setGraphics(graphics);
pageSize = pageDimension;
graphics.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON );
graphics.setRenderingHint( RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON );
setGraphicsState(new PDGraphicsState(new PDRectangle(widthPt, heightPt)));
return retval;
}
void setGraphics(Graphics2D graphics)
{
try {
Field field = PageDrawer.class.getDeclaredField("graphics");
field.setAccessible(true);
field.set(this, graphics);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static final int DEFAULT_USER_SPACE_UNIT_DPI = 72;
private static final Color TRANSPARENT_WHITE = new Color( 255, 255, 255, 0 );
private int imageType;
private int resolution;
}
如果要呈现给定PDPage page,的注释，则只需执行以下操作:
If you want to render the annotations of a given PDPage page, you merely do:
AnnotationDrawer drawer = new AnnotationDrawer(8, 288);
Map<String, BufferedImage> images = drawer.convertToImages(page);
构造函数参数与PDPage.convertToImage(int imageType, int resolution).
当心，这已经
a.根据PDFBox 1.8.2一起被黑客入侵；它可能包含特定于版本的代码； b.只检查了我在这里有一些可见的签名注释；它可能是不完整的，对于其他注释类型尤其如此.
a. been hacked together based on PDFBox 1.8.2; it may contain version-specific code; b. merely been checked for some visible signature annotations I have here; it may be incomplete, and it may especially fail for other annotation types.
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