void VP8EncInitAlpha(VP8Encoder* const enc) {
enc->has_alpha_ = WebPPictureHasTransparency(enc->pic_);
enc->alpha_data_ = NULL;
enc->alpha_data_size_ = 0;
if (enc->thread_level_ > 0) {
WebPWorker* const worker = &enc->alpha_worker_;
WebPWorkerInit(worker);
worker->data1 = enc;
worker->data2 = NULL;
worker->hook = (WebPWorkerHook)CompressAlphaJob;
}
}
// initialize the job struct with some TODOs
static void InitSegmentJob(VP8Encoder* const enc, SegmentJob* const job,
int start_row, int end_row) {
WebPWorkerInit(&job->worker);
job->worker.data1 = job;
job->worker.data2 = &job->it;
job->worker.hook = (WebPWorkerHook)DoSegmentsJob;
VP8IteratorInit(enc, &job->it);
VP8IteratorSetRow(&job->it, start_row);
VP8IteratorSetCountDown(&job->it, (end_row - start_row) * enc->mb_w_);
memset(job->alphas, 0, sizeof(job->alphas));
job->alpha = 0;
job->uv_alpha = 0;
// only one of both jobs can record the progress, since we don't
// expect the user's hook to be multi-thread safe
job->delta_progress = (start_row == 0) ? 20 : 0;
}