image cache preset

I have a content type with a cck field where i upload a image file. each time when i upload an image one image file is created in my directory and image cache directory and thumbnails directory.

I try to make a module to create content from this content type but i do not upload the image I just copy to direcory (ftp). now everything is fine but i can not do make that the image in thumbnails diretory and imagecache direcory be created.

somebody can help me