how to make a field that I can save a image?

I have try it like this:

    def _get_image(self, cr, uid, ids, name, args, context=None):
        result = dict.fromkeys(ids, False)
        for obj in self.browse(cr, uid, ids, context=context):
            result[obj.id] = tools.image_get_resized_images(obj.image)
        return result
    def _set_image(self, cr, uid, id, name, value, args, context=None):
        return self.write(cr, uid, [id], {'image': tools.image_resize_image_big(value)}, context=context)
'image': fields.binary("Image",
            help="This field holds the image used as image for our customers, limited to 1024x1024px."),

but this is not working. any help? thank you