问题描述
在IText XMLWorker中处理嵌入式图像。
Handling embedded images in IText XMLWorker.
有没有办法在XMLWorker中处理嵌入式（Base64）图像？在版本5.3.5
我使用的ImageProvider不再工作（之前引发异常），
所以我修补ImageRetrieve如下，但显然这将在下一个
XMLWorker中被破坏更新：
Is there a way to handle Embedded (Base64) images in XMLWorker? In version 5.3.5the ImageProvider I used does not work any more (an exception is raised before),so I Patched ImageRetrieve as follows, but obviously this will be broken in nextXMLWorker update:
package com.itextpdf.tool.xml.net;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import com.itextpdf.text.BadElementException;
import com.itextpdf.text.Image;
import com.itextpdf.text.pdf.codec.Base64;
import com.itextpdf.tool.xml.net.exc.NoImageException;
import com.itextpdf.tool.xml.pipeline.html.ImageProvider;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* @author redlab_b
*
*/
public class ImageRetrieve {
final static Pattern INLINE_PATTERN = Pattern.compile("^/data:image/(png|jpg|gif);base64,(.*)");
private final ImageProvider provider;
/**
* @param imageProvider the provider to use.
*
*/
public ImageRetrieve(final ImageProvider imageProvider) {
this.provider = imageProvider;
}
/**
*
*/
public ImageRetrieve() {
this.provider = null;
}
/**
* @param src an URI that can be used to retrieve an image
* @return an iText Image object
* @throws NoImageException if there is no image
* @throws IOException if an IOException occurred
*/
public com.itextpdf.text.Image retrieveImage(final String src) throws NoImageException, IOException {
com.itextpdf.text.Image img = null;
if (null != provider) {
img = provider.retrieve(src);
}
if (null == img) {
String path = null;
if (src.startsWith("http")) {
// full url available
path = src;
} else if (null != provider){
String root = this.provider.getImageRootPath();
if (null != root) {
if (root.endsWith("/") && src.startsWith("/")) {
root = root.substring(0, root.length() - 1);
}
path = root + src;
}
} else {
path = src;
}
if (null != path) {
try {
Matcher m;
if (path.startsWith("http")) {
img = com.itextpdf.text.Image.getInstance(path);
} else if ((m = INLINE_PATTERN.matcher(path)).matches()) {
// Let's handle the embedded image without saving it
try {
byte[] data = Base64.decode(m.group(2));
return Image.getInstance(data);
} catch (Exception ex) {
throw new NoImageException(src, ex);
}
} else {
img = com.itextpdf.text.Image.getInstance(new File(path).toURI().toURL());
}
if (null != provider && null != img) {
provider.store( src, img);
}
} catch (BadElementException e) {
throw new NoImageException(src, e);
} catch (MalformedURLException e) {
throw new NoImageException(src, e);
}
} else {
throw new NoImageException(src);
}
}
return img;
}
}
推荐答案
这几乎是你提出这个问题的年份，但也许这个答案无论如何都会有所帮助。
It's almost year since you asked this question, but maybe this answer will help anyway.
最近我遇到了类似的问题。我的目标是在生成的pdf中包含存储在数据库中的图像。
Recently I met similar problem. My goal was to include in generated pdf an image stored in database.
为此，我扩展了 com.itextpdf.tool.xml .pipeline.html.AbstractImageProvider 类并覆盖其 retrieve（）方法，如下所示：
To do this I've extended the com.itextpdf.tool.xml.pipeline.html.AbstractImageProvider class and overriden its retrieve() method like this:
public class MyImageProvider extends AbstractImageProvider {
@Override
public Image retrieve(final String src) {
Image img = super.retrieve(src);
if (img == null) {
try {
byte [] data = getMyImageSomehow(src);
img = Image.getInstance(data);
super.store(src, img);
}
catch (Exception e) {
//handle exceptions
}
}
return img;
}
@Override
public String getImageRootPath() {
return "http://sampleurl/img";
}
}
然后，在为XMLWorker [1]构建管道时，我将我的类的实例传递给上下文：
Then, when building pipelines for XMLWorker [1], I pass an instance of my class to context:
htmlPipelineContext.setImageProvider(new MyImageProvider());
现在我们希望这应该有效。但有一个问题！在某个地方，在xmlworker库的深处，正在克隆这个htmlPipelineContext。在此操作过程中，我们的ImageProvider实现会丢失。这发生在HtmlPipelineContext的clone（）方法中。看看第274-280行（我参考5.4.4版本）：
Now we would expect that this should work. But there's a catch! Somewhere, deep inside the xmlworker library, this htmlPipelineContext is being cloned. And during this operation our implementation of ImageProvider get's lost. This is happening inside HtmlPipelineContext's clone() method. Take a look at lines 274-280 (I refer to 5.4.4 version):
final String rootPath = imageProvider.getImageRootPath();
newCtx.setImageProvider(new AbstractImageProvider() {
public String getImageRootPath() {
return rootPath;
}
});
这甚至在HtmlPipelineContext.clone（）的javadoc [2]中有描述：
This is even described in HtmlPipelineContext.clone()'s javadoc [2]:
不是很有趣吗？你得到的类是为了扩展而设计的，但最后却证明，这个类只是作为一个属性持有者。
Isn't it funny? You get class that is designed for extending by making it abstract, but at the end it turns out, that this class serves only as a property holder.
我的解决方法：
public class MySpecialImageProviderAwareHtmlPipelineContext extends HtmlPipelineContext {
MySpecialImageProviderAwareHtmlPipelineContext () {
super(null);
}
public HtmlPipelineContext clone () {
HtmlPipelineContext ctx = null;
try {
ctx = super.clone();
ctx.setImageProvider(new MyImageProvider());
} catch (Exception e) {
//handle exception
}
return ctx;
}
}
然后我只是用它代替HtmlPipelineContext。
Then I just use this instead of HtmlPipelineContext.
[1]
[2]
这篇关于在IText XMLWorker中处理嵌入的图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！