How to access Topic name from pdfs using poppler? - pdf

Question

I am using poppler, and I want to access topic or headings of a particular page number using poppler, so please tell me how to do this using poppler.

Answer 1

Using the glib API. Don't know which API you want.
I'm pretty sure there is no topic/heading stored with a particular page.
You have to walk the index, if there is one.
Walk the index with backtracking. If you are lucky, each index node contains a PopplerActionGotoDest (check type!).
You can grab the title from the PopplerAction object (gchar *title) and get the page number from the included PopplerDest (int page_num).
page_num should be the first page of the section.
Assuming your PDF has an index containing PopplerActionGotoDest objects.
Then you simply walk it, checking for the page_num.
If page_num > searched_num, go back one step.
When you are at the correct parent, walk the childs. This should give you the best match.
I just made some code for it:
gchar* getTitle(PopplerIndexIter *iter, int num, PopplerIndexIter *last,PopplerDocument *doc)
{
int cur_num = 0;
int next;
PopplerAction * action;
PopplerDest * dest;
gchar * title = NULL;
PopplerIndexIter * last_tmp;
do
{
action = poppler_index_iter_get_action(iter);
if (action->type != POPPLER_ACTION_GOTO_DEST) {
printf("No GOTO_DEST!\n");
return NULL;
}
//get page number of current node
if (action->goto_dest.dest->type == POPPLER_DEST_NAMED) {
dest = poppler_document_find_dest (doc, action->goto_dest.dest->named_dest);
cur_num = dest->page_num;
poppler_dest_free(dest);
} else {
cur_num = action->goto_dest.dest->page_num;
}
//printf("cur_num: %d, %d\n",cur_num,num);
//free action, as we don't need it anymore
poppler_action_free(action);
//are there nodes following this one?
last_tmp = poppler_index_iter_copy(iter);
next = poppler_index_iter_next (iter);
//descend
if (!next || cur_num > num) {
if ((!next && cur_num < num) || cur_num == num) {
//descend current node
if (last) {
poppler_index_iter_free(last);
}
last = last_tmp;
}
//descend last node (backtracking)
if (last) {
/* Get the the action and do something with it */
PopplerIndexIter *child = poppler_index_iter_get_child (last);
gchar * tmp = NULL;
if (child) {
tmp = getTitle(child,num,last,doc);
poppler_index_iter_free (child);
} else {
action = poppler_index_iter_get_action(last);
if (action->type != POPPLER_ACTION_GOTO_DEST) {
tmp = NULL;
} else {
tmp = g_strdup (action->any.title);
}
poppler_action_free(action);
poppler_index_iter_free (last);
}
return tmp;
} else {
return NULL;
}
}
if (cur_num > num || (next && cur_num != 0)) {
// free last index_iter
if (last) {
poppler_index_iter_free(last);
}
last = last_tmp;
}
}
while (next);
return NULL;
}
getTitle gets called by:
for (i = 0; i < num_pages; i++) {
iter = poppler_index_iter_new (document);
title = getTitle(iter,i,NULL,document);
poppler_index_iter_free (iter);
if (title) {
printf("title of %d: %s\n",i, title);
g_free(title);
} else {
printf("%d: no title\n",i);
}
}