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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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include "src/decoder/physical_astc_block.h"
#include "src/decoder/types.h"
#include <array>
#include <vector>
namespace astc_codec {
// We use a special distinction for encode modes used to pass to the
// EncodeColorsForMode function below. The reason is that some of the color
// modes have sub-modes (like blue-contract) that change whether or not it is
// useful to encode an endpoint pair using one mode versus another. To avoid
// this problem, we approach the problem of encoding by specifying some
// high-level encoding modes. These eventually choose one of the low level
// ColorEndpointModes from Section C.2.14 when used in EncodeColorsForMode.
enum class EndpointEncodingMode {
// Returns the number of values in the encoded endpoint pair after encoding
// to a specific high-level encoding mode.
constexpr int NumValuesForEncodingMode(EndpointEncodingMode mode) {
mode == EndpointEncodingMode::kDirectLuma ? 2 :
mode == EndpointEncodingMode::kDirectLumaAlpha ? 4 :
mode == EndpointEncodingMode::kBaseScaleRGB ? 4 :
mode == EndpointEncodingMode::kBaseScaleRGBA ? 6 :
mode == EndpointEncodingMode::kDirectRGB ? 6 : 8;
// Fills |vals| with the quantized endpoint colors values defined in the ASTC
// specification. The values are quantized to the range [0, max_value]. These
// quantization limits can be obtained by querying the associated functions in
// integer_sequence_codec. The returned |astc_mode| will be the ASTC mode used
// to encode the resulting sequence.
// The |encoding_mode| is used to determine the way that we encode the values.
// Each encoding mode is used to determine which ASTC mode best corresponds
// to the pair of endpoints. It is a necessary hint to the encoding function
// in order to process the endpoints. Each encoding mode gurantees a certain
// number of values generated per endpoints.
// The return value will be true if the endpoints have been switched in order to
// reap the most benefit from the way the hardware decodes the given mode. In
// this case, the associated weights that interpolate this color must also be
// switched. In other words, for each w, it should change to 64 - w.
bool EncodeColorsForMode(
const RgbaColor& endpoint_low_rgba, const RgbaColor& endpoint_high_rgba,
int max_value, EndpointEncodingMode encoding_mode,
ColorEndpointMode* astc_mode, std::vector<int>* vals);
// Decodes the color values quantized to the range [0, max_value] into RGBA
// endpoints for the given mode. This function is the inverse of
// EncodeColorsForMode -- see that function for details. This function should
// work on all LDR endpoint modes, but no HDR modes.
void DecodeColorsForMode(const std::vector<int>& vals,
int max_value, ColorEndpointMode mode,
RgbaColor* endpoint_low_rgba,
RgbaColor* endpoint_high_rgba);
// Returns true if the quantized |vals| in the range [0, max_value] use the
// 'blue_contract' modification during decoding for the given |mode|.
bool UsesBlueContract(int max_value, ColorEndpointMode mode,
const std::vector<int>& vals);
} // namespace astc_codec