pdf - 如何使用 poppler 从 pdf 中访问主题名称？

Question

我正在使用 poppler，我想使用 poppler 访问特定页码的主题或标题，所以请告诉我如何使用 poppler 执行此操作。

Answer 1

使用 glib API。不知道你想要哪个 API。

我很确定特定页面中没有存储主题/标题。你必须走索引，如果有的话。

使用回溯遍历索引。如果幸运的话，每个索引节点都包含一个PopplerActionGotoDest（检查类型！）。您可以从 PopplerAction 对象 ( gchar *title ) 中获取标题，并从包含的PopplerDest ( int page_num ) 中获取页码。page_num 应该是该部分的第一页。

假设您的 PDF 有一个包含 PopplerActionGotoDest 对象的索引。然后你只需步行，检查page_num。如果 page_num > searched_num，则返回上一步。当您在正确的父母身边时，请带孩子走。这应该给你最好的匹配。我刚刚为它做了一些代码：

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被调用：

    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);
            }
    }