src/opts/SkBlitRow_opts.h

/*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkBlitRow_opts_DEFINED
#define SkBlitRow_opts_DEFINED

#include "Sk4px.h"

namespace SK_OPTS_NS {

// Color32 uses the blend_256_round_alt algorithm from tests/BlendTest.cpp.
// It's not quite perfect, but it's never wrong in the interesting edge cases,
// and it's quite a bit faster than blend_perfect.
//
// blend_256_round_alt is our currently blessed algorithm.  Please use it or an analogous one.
static void blit_row_color32(SkPMColor* dst, const SkPMColor* src, int count, SkPMColor color) {
    unsigned invA = 255 - SkGetPackedA32(color);
    invA += invA >> 7;
    SkASSERT(invA < 256);  // We've should have already handled alpha == 0 externally.

    Sk16h colorHighAndRound = Sk4px::DupPMColor(color).widenHi() + Sk16h(128);
    Sk16b invA_16x(invA);

    Sk4px::MapSrc(count, dst, src, [&](const Sk4px& src4) -> Sk4px {
        return (src4 * invA_16x).addNarrowHi(colorHighAndRound);
    });
}

}  // SK_OPTS_NS

#endif//SkBlitRow_opts_DEFINED