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Diffstat (limited to 'src/decoder/endpoint_codec.h')
-rw-r--r-- | src/decoder/endpoint_codec.h | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/src/decoder/endpoint_codec.h b/src/decoder/endpoint_codec.h new file mode 100644 index 0000000..a1232d0 --- /dev/null +++ b/src/decoder/endpoint_codec.h @@ -0,0 +1,90 @@ +// 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. + +#ifndef ASTC_CODEC_DECODER_ENDPOINT_CODEC_H_ +#define ASTC_CODEC_DECODER_ENDPOINT_CODEC_H_ + +#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 { + kDirectLuma, + kDirectLumaAlpha, + kBaseScaleRGB, + kBaseScaleRGBA, + kDirectRGB, + kDirectRGBA +}; + +// Returns the number of values in the encoded endpoint pair after encoding +// to a specific high-level encoding mode. +constexpr int NumValuesForEncodingMode(EndpointEncodingMode mode) { + return + 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 + +#endif // ASTC_CODEC_DECODER_ENDPOINT_CODEC_H_ |