TableLookUp.cpp

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/*
    RawSpeed - RAW file decoder.
 
    Copyright (C) 2009-2014 Klaus Post
    Copyright (C) 2017 Roman Lebedev
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.
 
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.
 
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
 
#include "common/TableLookUp.h"
#include "adt/Array1DRef.h"
#include "adt/Array2DRef.h"
#include "adt/Bit.h"
#include "adt/Casts.h"
#include "adt/Invariant.h"
#include "decoders/RawDecoderException.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <limits>
#include <vector>
 
namespace rawspeed {
 
// How many different values can uint16_t represent?
constexpr int TABLE_MAX_ELTS = std::numeric_limits<uint16_t>::max() + 1;
constexpr int TABLE_SIZE = TABLE_MAX_ELTS * 2;
 
// Creates n numre of tables.
TableLookUp::TableLookUp(int _ntables, bool _dither)
    : ntables(_ntables), dither(_dither) {
  if (ntables < 1) {
    ThrowRDE("Cannot construct 0 tables");
  }
  tables.resize(ntables * TABLE_SIZE, uint16_t(0));
}
 
void TableLookUp::setTable(int ntable, const std::vector<uint16_t>& table) {
  assert(!table.empty());
 
  const auto nfilled = implicit_cast<int>(table.size());
  if (nfilled > TABLE_MAX_ELTS)
    ThrowRDE("Table lookup with %i entries is unsupported", nfilled);
 
  if (ntable > ntables) {
    ThrowRDE("Table lookup with number greater than number of tables.");
  }
 
  auto t = Array2DRef(tables.data(), TABLE_SIZE, ntables)[ntable];
  if (!dither) {
    for (int i = 0; i < TABLE_MAX_ELTS; i++) {
      t(i) = (i < nfilled) ? table[i] : table[nfilled - 1];
    }
    return;
  }
  for (int i = 0; i < nfilled; i++) {
    int center = table[i];
    int lower = i > 0 ? table[i - 1] : center;
    int upper = i < (nfilled - 1) ? table[i + 1] : center;
    // Non-monotonic LUT handling: don't interpolate across the cross-over.
    lower = std::min(lower, center);
    upper = std::max(upper, center);
    int delta = upper - lower;
    invariant(delta >= 0);
    t(i * 2) = clampBits(center - ((upper - lower + 2) / 4), 16);
    t((i * 2) + 1) = implicit_cast<uint16_t>(delta);
  }
 
  for (int i = nfilled; i < TABLE_MAX_ELTS; i++) {
    t(i * 2) = table[nfilled - 1];
    t((i * 2) + 1) = 0;
  }
}
 
Array1DRef<uint16_t> TableLookUp::getTable(int n) {
  if (n > ntables) {
    ThrowRDE("Table lookup with number greater than number of tables.");
  }
  return Array2DRef(tables.data(), TABLE_SIZE, ntables)[n];
}
 
} // namespace rawspeed