static int EmitRescaledAlphaYUV(const VP8Io* const io, WebPDecParams* const p) {
if (io->a != NULL) {
const WebPYUVABuffer* const buf = &p->output->u.YUVA;
uint8_t* dst_y = buf->y + p->last_y * buf->y_stride;
const uint8_t* src_a = buf->a + p->last_y * buf->a_stride;
const int num_lines_out = Rescale(io->a, io->width, io->mb_h, &p->scaler_a);
if (num_lines_out > 0) { // unmultiply the Y
WebPMultRows(dst_y, buf->y_stride, src_a, buf->a_stride,
p->scaler_a.dst_width, num_lines_out, 1);
}
}
return 0;
}
static int EmitRescaledYUV(const VP8Io* const io, WebPDecParams* const p) {
const int mb_h = io->mb_h;
const int uv_mb_h = (mb_h + 1) >> 1;
WebPRescaler* const scaler = p->scaler_y;
int num_lines_out = 0;
if (WebPIsAlphaMode(p->output->colorspace) && io->a != NULL) {
// Before rescaling, we premultiply the luma directly into the io->y
// internal buffer. This is OK since these samples are not used for
// intra-prediction (the top samples are saved in cache_y_/u_/v_).
// But we need to cast the const away, though.
WebPMultRows((uint8_t*)io->y, io->y_stride,
io->a, io->width, io->mb_w, mb_h, 0);
}
num_lines_out = Rescale(io->y, io->y_stride, mb_h, scaler);
Rescale(io->u, io->uv_stride, uv_mb_h, p->scaler_u);
Rescale(io->v, io->uv_stride, uv_mb_h, p->scaler_v);
return num_lines_out;
}
static int EmitRescaledAlphaYUV(const VP8Io* const io, WebPDecParams* const p,
int expected_num_lines_out) {
const WebPYUVABuffer* const buf = &p->output->u.YUVA;
uint8_t* const dst_a = buf->a + p->last_y * buf->a_stride;
if (io->a != NULL) {
uint8_t* const dst_y = buf->y + p->last_y * buf->y_stride;
const int num_lines_out = Rescale(io->a, io->width, io->mb_h, p->scaler_a);
assert(expected_num_lines_out == num_lines_out);
if (num_lines_out > 0) { // unmultiply the Y
WebPMultRows(dst_y, buf->y_stride, dst_a, buf->a_stride,
p->scaler_a->dst_width, num_lines_out, 1);
}
} else if (buf->a != NULL) {
// the user requested alpha, but there is none, set it to opaque.
assert(p->last_y + expected_num_lines_out <= io->scaled_height);
FillAlphaPlane(dst_a, io->scaled_width, expected_num_lines_out,
buf->a_stride);
}
return 0;
}
