in imageops.c [160:168]
void image_flip_left_right(ImageObject* self) {
IppiSize roi = { self->width, self->height };
IppStatus ipp_status = ippiMirror_8u_C3IR(
self->buffer + (self->y_offset * self->row_stride + self->x_offset) * self->channels,
self->row_stride * self->channels,
roi, ippAxsVertical);
if (ipp_status != ippStsNoErr)
PyErr_Format(PyExc_SystemError, "ippiMirror_8u_C3IR failed with status %d", ipp_status);
}