I'm using apache PDFBox from java, and I have a source PDF with multiple optional content groups. What I am wanting to do is export a version of the PDF that includes only the standard content and the optional content groups that were enabled. It is important for my purposes that I preserve any dynamic aspects of the original.... so text fields are still text fields, vector images are still vector images, etc. The reason that this is required is because I intend to ultimately be using a pdf form editor program that does not know how to handle optional content, and would blindly render all of them, so I want to preprocess the source pdf, and use the form editing program on a less cluttered destination pdf.
I've been trying to find something that could give me any hints on how to do this with google, but to no avail. I don't know if I'm just using the wrong search terms, or if this is just something that is outside of what the PDFBox API was designed for. I rather hope it's not the latter. The info shown here does not seem to work (converting the C# code to java), because despite the pdf I'm trying to import having optional content, there does not seem to be any OC resources when I examine the tokens on each page.
for(PDPage page:pages) {
PDResources resources = page.getResources();
PDFStreamParser parser = new PDFStreamParser(page);
parser.parse();
Collection tokens = parser.getTokens();
...
}
I'm truly sorry for not having any more code to show what I've tried so far, but I've just been poring over the java API docs for about 8 hours now trying to figure out what I might need to do this, and just haven't been able to figure it out.
What I DO know how to do is add text, lines, and images to a new PDPage, but I do not know how to retrieve that information from a given source page to copy it over, nor how to tell which optional content group such information is part of (if any). I am also not sure how to copy form fields in the source pdf over to the destination, nor how to copy the font information over.
Honestly, if there's a web page out there that I wasn't able to find with google with the searches that I tried, I'd be entirely happy to read up more about it, but I am really quite stuck here, and I don't know anyone personally that knows about this library.
Please help.
EDIT: Trying what I understand from what was suggested below, I've written a loop to examine each XObject on the page as follows:
PDResources resources = pdPage.getResources();
Iterable<COSName> names = resources.getXObjectNames();
for(COSName name:names) {
PDXObject xobj = resources.getXObject(name);
PDFStreamParser parser = new PDFStreamParser(xobj.getStream().toByteArray());
parser.parse();
Object [] tokens = parser.getTokens().toArray();
for(int i = 0;i<tokens.length-1;i++) {
Object obj = tokens[i];
if (obj instanceof COSName && obj.equals(COSName.OC)) {
i++;
Object obj = tokens[i];
if (obj instanceof COSName) {
PDPropertyList props = resources.getProperties((COSName)obj);
if (props != null) {
...
However, after an OC key, the next entry in the tokens
array is always an Operator
tagged as "BMC". Nowhere am I finding any info that I can recognize from the named optional content groups.