from FileMetadataExtractor import FileMetadataExtractor
import os
from RSS import ns
import PNG

class PngCommentExtractor(FileMetadataExtractor):
    def extract(self, f, item):
        if os.path.splitext(f)[1] != ".png": return
        png = PNG.Png.open(file(f, 'rb'))
        def get(keyword):
            # TODO: handle zTXt and iTXt
            return "; ".join([c.content for c in png.get_chunks(PNG.tEXt) if c.keyword==keyword]).strip()
        def set(tag, keyword):
            t = get(keyword)
            if t:
                item[tag] = t
        set((ns.rss10, 'title'), 'Title')
        set((ns.rss10, 'description'), 'Description')
        set((ns.dc, 'creator'), 'Author')