java - 使用itext库在pdf文档中添加内联图像

Question

我们创建了一个使用itext 5库生成pdf文档的应用程序。作为pdf生成的一部分，我们试图将图像内嵌在pdf中，该图像应不可编辑且只读。我们尝试使用PdfContentByte的addImage方法，如下所示，

byte[] decoded = Base64.getDecoder().decode(encodedImage);
image = Image.getInstance(decoded);

检索此图像后，在addImage方法中使用相同的图像。

PdfContentByte canvas =  pdfStamper.getOverContent(item.getPage(0));
canvas.addImage(image, Boolean.TRUE);

结果：由于该图像为Base 64字符串格式，因此该图像不会显示在生成的pdf文档中（如果该图像不是Base 64格式，则可以正常工作）。

当我们打开pdf时，显示以下错误：------->“此页面上存在错误。Acrobat可能无法正确显示该页面。请与创建PDF文档的人联系以更正此问题。 ”

我们如何处理这种情况？

是否有其他方法可以达到此要求。请帮忙

代码：-

PdfReader resultantPdfReader = new PdfReader("template.pdf");

PdfStamper resultandPdfStamper = new PdfStamper(resultantPdfReader, new FileOutputStream("A13.pdf"));

AcroFields acroFields = resultantPdfReader.getAcroFields();
Rectangle fieldPosRec = acroFields.getFieldPositions("imageField").get(0).position;

String encodedSignature = ""; 
encodedSignature = new String(Files.readAllBytes(Paths.get("MyImage.png")));

if(encodedSignature.indexOf("data:image/png;base64,") != -1) {
    encodedSignature = encodedSignature.substring("data:image/png;base64,".length());
}

Image image = null;
try {
    byte[] decoded = Base64.getDecoder().decode(encodedSignature);
    image = Image.getInstance(decoded);
} catch (Exception e) {
    e.printStackTrace();
}
image.scaleAbsoluteHeight(fieldPosRec.getHeight());
image.scaleAbsoluteWidth(fieldPosRec.getWidth());
image.scaleToFit(fieldPosRec);
acroFields.removeField("imageField");                                              
image.setAbsolutePosition(fieldPosRec.getLeft(), fieldPosRec.getBottom());
PdfContentByte canvas = resultandPdfStamper.getOverContent(item.getPage(0));
canvas.addImage(image, Boolean.TRUE);
resultandPdfStamper.close();
resultantPdfReader.close();

BASE64图像串：iVBORw0KGgoAAAANSUhEUgAAAU4AAACWCAYAAACxSWGfAAAAAXNSR0IArs4c6QAAFJFJREFUeAHtnQmwZFV9hw37DgoiaJgZsGBAFgkSIEJgjAZRAliFikrEoOgoGkQlEFJKiXFhr5RCAKMjJhBETAoRImjAB4KAKBgEDBBhQM2IyEDYh2XM90Gf8k7T3a / fe9093X1 // 6rv3XOXvsvX9 / 773HNP93vBCxIxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAMxEAPNBl7MhEObJ2Y8BmIgBmKgtYG9mTwBv2vAIBEDMRADMdDKwCuYeCmUhFmGrZbNtBiIgRhoa2AN5uwDZ8L3oCST6Q6vYR3nwnyYC8MQ67MTp8JT4HEthsMbZccTMRADMTCpgU1Z4kPwbXgCppsku3ndIta / vBLpymz7w2CidF9NnCZQE6lR9v + 5sfyNgRiIgYqBlSjvASfALVAShsNn4Br4OPwRzDSsZc4Hk + UiqG7LstOcNx / mQj9iM1Z6LFwNZfveonurXmJVCmVemZZhDMRAzQ1swPG / E74GD0BJEg4dPw8OAp8u9zNMjibJc2ERVPfDstOcNx / mwnRjLV54MFwBS6Fsx3X7MKg5jmeCyxzXPCPjnQ38QefZmRsDI2dge / bYJCE7wwpQ4mcULm5wFcOny4wBD02O8yps1LR9b6sfhvsa / GaS8k7M / 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Answer 1

您的示例图像具有iText无法正确转换为嵌入式图像的属性。不幸的是，它无法识别并输出错误的结果PDF。

特别是您的图像文件使用透明度。内联图像不允许使用Mask或SMask条目（PDF中的图像用来表示透明度）。因此，您的图像不能用作嵌入式图像。

结果，由iText创建的嵌入式图像仅由黑色矩形组成，而透明度信息（包含线条图）被删除。

此外，您的图像使用校准的RGB颜色空间。此类已校准的RGB颜色空间本身无法内联，因此必须将颜色空间定义放入页面资源中。但是，iText在创建内联图像时无法正确引用该非内联部分。

结果，由iText创建的嵌入式图像以错误的名称引用了色彩空间，从而导致Adobe Reader出现“此页面上存在错误”错误消息。修复该参考对象将获得有效结果PDF，该结果显示上述黑色矩形。



在评论中，您说明您的实际目标是防止从生成的pdf文档中复制图像。

通常，这显然是不可能的-PDF查看器可以访问的在屏幕或纸张上绘制的任何信息，也可以由设计用于该任务的PDF处理器访问，以复制到某些文件。 （让我们在这里忽略专有的，特定于查看器的DRM扩展。）

但是，您可以尝试以一种常见的PDF查看器不提供复制数据的方式来绘制数据。像您一样尝试使用内联图像是该方向的一种方法。其他方法将图像包装在其他结构中，例如以一种模式：

PdfContentByte canvas = resultandPdfStamper.getOverContent(1);
Rectangle pageSize = resultantPdfReader.getPageSize(1);
PdfPatternPainter painter = canvas.createPattern(pageSize.getWidth(), pageSize.getHeight());
painter.addImage(image);
canvas.setColorFill(new PatternColor(painter));
canvas.rectangle(0, 0, pageSize.getWidth(), pageSize.getHeight());
canvas.fill();

（ AddImageInPattern测试 testAddToPageTest3）

Adobe Acrobat Reader此处不提供复制该图像的功能。另外，我的（公认较旧的）Adobe Acrobat Pro不提供复制它的功能，仅是将其删除（更确切地说，是删除填充有图案的整个矩形）。

但是要注意，普通的PDF查看器提供或不提供的是一个移动的目标...