godot/thirdparty/libwebp/src/dsp/lossless_common.h

// Copyright 2012 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Image transforms and color space conversion methods for lossless decoder.
//
// Authors: Vikas Arora ([email protected])
//          Jyrki Alakuijala ([email protected])
//          Vincent Rabaud ([email protected])

#ifndef WEBP_DSP_LOSSLESS_COMMON_H_
#define WEBP_DSP_LOSSLESS_COMMON_H_

#include "src/dsp/cpu.h"
#include "src/utils/utils.h"
#include "src/webp/types.h"

#ifdef __cplusplus
extern "C" {
#endif

//------------------------------------------------------------------------------
// Decoding

// color mapping related functions.
static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) { … }

static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) { … }

static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) { … }

static WEBP_INLINE uint8_t VP8GetAlphaValue(uint32_t val) { … }

//------------------------------------------------------------------------------
// Misc methods.

// Computes sampled size of 'size' when sampling using 'sampling bits'.
static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
                                              uint32_t sampling_bits) { … }

// Converts near lossless quality into max number of bits shaved off.
static WEBP_INLINE int VP8LNearLosslessBits(int near_lossless_quality) { … }

// -----------------------------------------------------------------------------
// Faster logarithm for integers. Small values use a look-up table.

// The threshold till approximate version of log_2 can be used.
// Practically, we can get rid of the call to log() as the two values match to
// very high degree (the ratio of these two is 0.99999x).
// Keeping a high threshold for now.
#define APPROX_LOG_WITH_CORRECTION_MAX …
#define APPROX_LOG_MAX …
#define LOG_2_RECIPROCAL …
#define LOG_LOOKUP_IDX_MAX …
extern const float kLog2Table[LOG_LOOKUP_IDX_MAX];
extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX];
VP8LFastLog2SlowFunc;

extern VP8LFastLog2SlowFunc VP8LFastLog2Slow;
extern VP8LFastLog2SlowFunc VP8LFastSLog2Slow;

static WEBP_INLINE float VP8LFastLog2(uint32_t v) { … }
// Fast calculation of v * log2(v) for integer input.
static WEBP_INLINE float VP8LFastSLog2(uint32_t v) { … }

// -----------------------------------------------------------------------------
// PrefixEncode()

// Splitting of distance and length codes into prefixes and
// extra bits. The prefixes are encoded with an entropy code
// while the extra bits are stored just as normal bits.
static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code,
                                                  int* const extra_bits) { … }

static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code,
                                              int* const extra_bits,
                                              int* const extra_bits_value) { … }

#define PREFIX_LOOKUP_IDX_MAX …
VP8LPrefixCode;

// These tables are derived using VP8LPrefixEncodeNoLUT.
extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX];
extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX];
static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code,
                                             int* const extra_bits) { … }

static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code,
                                         int* const extra_bits,
                                         int* const extra_bits_value) { … }

// Sum of each component, mod 256.
static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
uint32_t VP8LAddPixels(uint32_t a, uint32_t b) { … }

// Difference of each component, mod 256.
static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
uint32_t VP8LSubPixels(uint32_t a, uint32_t b) { … }

//------------------------------------------------------------------------------
// Transform-related functions used in both encoding and decoding.

// Macros used to create a batch predictor that iteratively uses a
// one-pixel predictor.

// The predictor is added to the output pixel (which
// is therefore considered as a residual) to get the final prediction.
#define GENERATE_PREDICTOR_ADD(PREDICTOR, PREDICTOR_ADD) …

#ifdef __cplusplus
}    // extern "C"
#endif

#endif  // WEBP_DSP_LOSSLESS_COMMON_H_