godot/thirdparty/astcenc/astcenc_compress_symbolic.cpp

// SPDX-License-Identifier: Apache-2.0
// ----------------------------------------------------------------------------
// Copyright 2011-2024 Arm Limited
//
// 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:
//
//     http://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.
// ----------------------------------------------------------------------------

#if !defined(ASTCENC_DECOMPRESS_ONLY)

/**
 * @brief Functions to compress a symbolic block.
 */

#include "astcenc_internal.h"
#include "astcenc_diagnostic_trace.h"

#include <cassert>

/**
 * @brief Merge two planes of endpoints into a single vector.
 *
 * @param      ep_plane1          The endpoints for plane 1.
 * @param      ep_plane2          The endpoints for plane 2.
 * @param      component_plane2   The color component for plane 2.
 * @param[out] result             The merged output.
 */
static void merge_endpoints(
	const endpoints& ep_plane1,
	const endpoints& ep_plane2,
	unsigned int component_plane2,
	endpoints& result
) { … }

/**
 * @brief Attempt to improve weights given a chosen configuration.
 *
 * Given a fixed weight grid decimation and weight value quantization, iterate over all weights (per
 * partition and per plane) and attempt to improve image quality by moving each weight up by one or
 * down by one quantization step.
 *
 * This is a specialized function which only supports operating on undecimated weight grids,
 * therefore primarily improving the performance of 4x4 and 5x5 blocks where grid decimation
 * is needed less often.
 *
 * @param      decode_mode   The decode mode (LDR, HDR).
 * @param      bsd           The block size information.
 * @param      blk           The image block color data to compress.
 * @param[out] scb           The symbolic compressed block output.
 */
static bool realign_weights_undecimated(
	astcenc_profile decode_mode,
	const block_size_descriptor& bsd,
	const image_block& blk,
	symbolic_compressed_block& scb
) { … }

/**
 * @brief Attempt to improve weights given a chosen configuration.
 *
 * Given a fixed weight grid decimation and weight value quantization, iterate over all weights (per
 * partition and per plane) and attempt to improve image quality by moving each weight up by one or
 * down by one quantization step.
 *
 * @param      decode_mode   The decode mode (LDR, HDR).
 * @param      bsd           The block size information.
 * @param      blk           The image block color data to compress.
 * @param[out] scb           The symbolic compressed block output.
 */
static bool realign_weights_decimated(
	astcenc_profile decode_mode,
	const block_size_descriptor& bsd,
	const image_block& blk,
	symbolic_compressed_block& scb
) { … }

/**
 * @brief Compress a block using a chosen partitioning and 1 plane of weights.
 *
 * @param      config                    The compressor configuration.
 * @param      bsd                       The block size information.
 * @param      blk                       The image block color data to compress.
 * @param      only_always               True if we only use "always" percentile block modes.
 * @param      tune_errorval_threshold   The error value threshold.
 * @param      partition_count           The partition count.
 * @param      partition_index           The partition index if @c partition_count is 2-4.
 * @param[out] scb                       The symbolic compressed block output.
 * @param[out] tmpbuf                    The quantized weights for plane 1.
 */
static float compress_symbolic_block_for_partition_1plane(
	const astcenc_config& config,
	const block_size_descriptor& bsd,
	const image_block& blk,
	bool only_always,
	float tune_errorval_threshold,
	unsigned int partition_count,
	unsigned int partition_index,
	symbolic_compressed_block& scb,
	compression_working_buffers& tmpbuf,
	int quant_limit
) { … }

/**
 * @brief Compress a block using a chosen partitioning and 2 planes of weights.
 *
 * @param      config                    The compressor configuration.
 * @param      bsd                       The block size information.
 * @param      blk                       The image block color data to compress.
 * @param      tune_errorval_threshold   The error value threshold.
 * @param      plane2_component          The component index for the second plane of weights.
 * @param[out] scb                       The symbolic compressed block output.
 * @param[out] tmpbuf                    The quantized weights for plane 1.
 */
static float compress_symbolic_block_for_partition_2planes(
	const astcenc_config& config,
	const block_size_descriptor& bsd,
	const image_block& blk,
	float tune_errorval_threshold,
	unsigned int plane2_component,
	symbolic_compressed_block& scb,
	compression_working_buffers& tmpbuf,
	int quant_limit
) { … }

/**
 * @brief Determine the lowest cross-channel correlation factor.
 *
 * @param texels_per_block   The number of texels in a block.
 * @param blk                The image block color data to compress.
 *
 * @return Return the lowest correlation factor.
 */
static float prepare_block_statistics(
	int texels_per_block,
	const image_block& blk
) { … }

/* See header for documentation. */
void compress_block(
	const astcenc_contexti& ctx,
	const image_block& blk,
	uint8_t pcb[16],
	compression_working_buffers& tmpbuf)
{ … }

#endif