python - PDFrwを使用してPDFから画像を抽出する方法

Question

私はPDFrwその例の1つを使用して、PFDファイル内の唯一の画像を抽出し、その画像をPNGまたはJPEGファイルに保存しています。

コードが難しすぎて理解できません。どのパラメータに渡す必要がありfind_objectsますか?

from pdfrw.objects import PdfDict, PdfArray, PdfName
from pdfrw.pdfwriter import user_fmt


def find_objects(source, valid_types=(PdfName.XObject, None),
                 valid_subtypes=(PdfName.Form, PdfName.Image),
                 no_follow=(PdfName.Parent,),
                 isinstance=isinstance, id=id, sorted=sorted,
                 reversed=reversed, PdfDict=PdfDict):
    '''
        Find all the objects of a particular kind in a document
        or array.  Defaults to looking for Form and Image XObjects.
        This could be done recursively, but some PDFs
        are quite deeply nested, so we do it without
        recursion.
        Note that we don't know exactly where things appear on pages,
        but we aim for a sort order that is (a) mostly in document order,
        and (b) reproducible.  For arrays, objects are processed in
        array order, and for dicts, they are processed in key order.
    '''
    container = (PdfDict, PdfArray)

    # Allow passing a list of pages, or a dict
    if isinstance(source, PdfDict):
        source = [source]
    else:
        source = list(source)

    visited = set()
    source.reverse()
    while source:
        obj = source.pop()
        if not isinstance(obj, container):
            continue
        myid = id(obj)
        if myid in visited:
            continue
        visited.add(myid)
        if isinstance(obj, PdfDict):
            if obj.Type in valid_types and obj.Subtype in valid_subtypes:
                yield obj
            obj = [y for (x, y) in sorted(obj.iteritems())
                   if x not in no_follow]
        else:
            # TODO: This forces resolution of any indirect objects in
            # the array.  It may not be necessary.  Don't know if
            # reversed() does any voodoo underneath the hood.
            # It's cheap enough for now, but might be removeable.
            obj and obj[0]
        source.extend(reversed(obj))


find_objects('target.pdf')