How can I get ByteRange with iText7? - itext

Question

As the picture show , I need to get byte array from ByteRange to do some verify , they are 0 to 840 and 960 to 1200.
I found the similar question : In Itext 7, how to get the range stream to sign a pdf?

Answer 1

iText in its own verification code needs to do the same thing. It does so in its SignatureUtil class. Thus, one can simply borrow from that code, e.g. like this:
try ( PdfReader pdfReader = new PdfReader(SOURCE_PDF);
PdfDocument pdfDocument = new PdfDocument(pdfReader);) {
SignatureUtil signatureUtil = new SignatureUtil(pdfDocument);
for (String name : signatureUtil.getSignatureNames()) {
PdfSignature signature = signatureUtil.getSignature(name);
PdfArray b = signature.getByteRange();
RandomAccessFileOrArray rf = pdfReader.getSafeFile();
try ( InputStream rg = new RASInputStream(new RandomAccessSourceFactory().createRanged(rf.createSourceView(), SignatureUtil.asLongArray(b)));
OutputStream result = TARGET_STREAM_FOR_name_BYTES) {
byte[] buf = new byte[8192];
int rd;
while ((rd = rg.read(buf, 0, buf.length)) > 0) {
result.write(buf, 0, rd);
}
}
}
}
(RetrieveSignedRanges test testExtractSignedBytes)
If you want the byte range as a byte[] in memory, you can use a ByteArrayOutputStream as TARGET_STREAM_FOR_name_BYTES and retrieve the resulting byte array from it.