Duplicate watermark applied to changed images

This issue has already been mentioned for 4.7 here: http://drupal.org/node/81327 However, in 5.0 it is still persists. I have mass-uploaded lots of images and tried to edit some of them - watermark applies twice and makes pictures ugly. Is it possible make the code to pre-check every picture if it already has or not watermark, and to apply only if it a picture does not have watermark?