PGPUserAttributeSubpacketVectorGenerator vGen = new PGPUserAttributeSubpacketVectorGenerator();
vGen.setImageAttribute(ImageAttribute.JPEG, jpegImage);
PGPUserAttributeSubpacketVector uVec = vGen.generate();
PGPSignatureGenerator sGen = new PGPSignatureGenerator(PublicKeyAlgorithmTags.RSA_GENERAL, HashAlgorithmTags.SHA1, "BC");
sGen.initSign(PGPSignature.POSITIVE_CERTIFICATION, pgpSec.getSecretKey().extractPrivateKey(pass, "BC"));