itext解析pdf中签章文件的证书

itext可以生成pdf并对其进行各种操作，其中就包括签章，并且用其他工具签的章，itext也可以识别出来。

目前系统中有一个需求，系统要求上传的pdf必须进行签章，上传后需要对pdf进行验签和拿到pdf章的证书的所有者，

拿到章证书的所有者代码如下

<pre name="code" class="java"> PdfReader reader = new PdfReader(pdfPath);
AcroFields acroFields = reader.getAcroFields();
if (acroFields == null) {
return result;
}
List&lt;String&gt; signatureNames = acroFields.getSignatureNames();
if (signatureNames == null || signatureNames.size() == 0) {
return result;
}
reader.close();
for (String str : signatureNames) {
PdfDictionary sigDict = acroFields.getSignatureDictionary(str);
if (sigDict == null) {
continue;
}
PdfName sub = sigDict.getAsName(PdfName.SUBFILTER);
if (PdfName.ADBE_X509_RSA_SHA1.equals(sub)) {
PdfString certStr = sigDict.getAsString(PdfName.CERT);
if (certStr == null) {
certStr = sigDict.getAsArray(PdfName.CERT).getAsString(0);
}
if (certStr == null) {
continue;
}
X509CertParser certParser = new X509CertParser();
certParser.engineInit(new ByteArrayInputStream(certStr.getBytes()));
Collection&lt;Certificate&gt; certs = certParser.engineReadAll();
if (certs == null || certs.size() == 0) {
continue;
}
X509Certificate certificate = (X509Certificate) certs.iterator().next();
if (certificate == null) {
continue;
}
X500Principal principal = certificate.getSubjectX500Principal();
if (principal == null) {
continue;
}
LdapName ldapDN = new LdapName(principal.getName());
for (Rdn rdn : ldapDN.getRdns()) {
if ("CN".equals(rdn.getType())) {
result.add((String) rdn.getValue());
}
}
}
}</pre>

我有一个问题关于pdf conversion的，pdf to JPG conversion处理之后的图片能否在转换过程中调整尺寸吗？