product_images.py

from openerp import models, fields, api


class product_image(models.Model):
    _name = 'product.image'
    _order = 'sequence, id DESC'

    name = fields.Char('Name')
    description = fields.Text('Description')
    sequence = fields.Integer('Sequence')
    image_alt = fields.Text('Image Label')
    image = fields.Binary('Image')
    image_small = fields.Binary('Small Image')
    product_tmpl_id = fields.Many2one('product.template', 'Product', select=True)
    from_main_image = fields.Boolean('From Main Image', default=False)


class product_product(models.Model):
    _inherit = 'product.product'

    images = fields.One2many('product.image', related='product_tmpl_id.images',
                             string='Images', store=False)


class product_template(models.Model):
    _inherit = 'product.template'

    images = fields.One2many('product.image', 'product_tmpl_id',
                             string='Images')

    @api.one
    def action_copy_image_to_images(self):
        if not self.image:
            return
        image = None
        for r in self.images:
            if r.from_main_image:
                image = r
                break

        if image:
            image.image = self.image
        else:
            vals = {'image': self.image,
                    'name': self.name,
                    'product_tmpl_id': self.id,
                    'from_main_image': True, }
            self.env['product.image'].create(vals)