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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "src/decoder/weight_infill.h"
#include "src/decoder/integer_sequence_codec.h"
#include <array>
#include <cmath>
#include <utility>
namespace astc_codec {
namespace {
// The following functions are based on Section C.2.18 of the ASTC specification
int GetScaleFactorD(int block_dim) {
return static_cast<int>((1024.f + static_cast<float>(block_dim >> 1)) /
static_cast<float>(block_dim - 1));
}
std::pair<int, int> GetGridSpaceCoordinates(
Footprint footprint, int s, int t, int weight_dim_x, int weight_dim_y) {
const int ds = GetScaleFactorD(footprint.Width());
const int dt = GetScaleFactorD(footprint.Height());
const int cs = ds * s;
const int ct = dt * t;
const int gs = (cs * (weight_dim_x - 1) + 32) >> 6;
const int gt = (ct * (weight_dim_y - 1) + 32) >> 6;
assert(gt < 1 << 8);
assert(gs < 1 << 8);
return std::make_pair(gs, gt);
}
// Returns the weight-grid values that are to be used for bilinearly
// interpolating the weight to its final value. If the returned value
// is equal to weight_dim_x * weight_dim_y, it may be ignored.
std::array<int, 4> BilerpGridPointsForWeight(
const std::pair<int, int>& grid_space_coords, int weight_dim_x) {
const int js = grid_space_coords.first >> 4;
const int jt = grid_space_coords.second >> 4;
std::array<int, 4> result;
result[0] = js + weight_dim_x * jt;
result[1] = js + weight_dim_x * jt + 1;
result[2] = js + weight_dim_x * (jt + 1);
result[3] = js + weight_dim_x * (jt + 1) + 1;
return result;
}
std::array<int, 4> BilerpGridPointFactorsForWeight(
const std::pair<int, int>& grid_space_coords) {
const int fs = grid_space_coords.first & 0xF;
const int ft = grid_space_coords.second & 0xF;
std::array<int, 4> result;
result[3] = (fs * ft + 8) >> 4;
result[2] = ft - result[3];
result[1] = fs - result[3];
result[0] = 16 - fs - ft + result[3];
assert(result[0] <= 16);
assert(result[1] <= 16);
assert(result[2] <= 16);
assert(result[3] <= 16);
return result;
}
} // namespace
////////////////////////////////////////////////////////////////////////////////
int CountBitsForWeights(int weight_dim_x, int weight_dim_y,
int target_weight_range) {
int num_weights = weight_dim_x * weight_dim_y;
return IntegerSequenceCodec::
GetBitCountForRange(num_weights, target_weight_range);
}
std::vector<int> InfillWeights(const std::vector<int>& weights,
Footprint footprint, int dim_x, int dim_y) {
std::vector<int> result;
result.reserve(footprint.NumPixels());
for (int t = 0; t < footprint.Height(); ++t) {
for (int s = 0; s < footprint.Width(); ++s) {
const auto grid_space_coords =
GetGridSpaceCoordinates(footprint, s, t, dim_x, dim_y);
const auto grid_pts =
BilerpGridPointsForWeight(grid_space_coords, dim_x);
const auto grid_factors =
BilerpGridPointFactorsForWeight(grid_space_coords);
int weight = 0;
for (int i = 0; i < 4; ++i) {
if (grid_pts[i] < dim_x * dim_y) {
weight += weights.at(grid_pts[i]) * grid_factors[i];
}
}
result.push_back((weight + 8) >> 4);
}
}
return result;
}
} // namespace astc_codec
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