chromium/third_party/libwebp/src/sharpyuv/sharpyuv_gamma.c

// Copyright 2022 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.
// -----------------------------------------------------------------------------
//
// Gamma correction utilities.

#include "sharpyuv/sharpyuv_gamma.h"

#include <assert.h>
#include <float.h>
#include <math.h>

#include "src/webp/types.h"

// Gamma correction compensates loss of resolution during chroma subsampling.
// Size of pre-computed table for converting from gamma to linear.
#define GAMMA_TO_LINEAR_TAB_BITS …
#define GAMMA_TO_LINEAR_TAB_SIZE …
static uint32_t kGammaToLinearTabS[GAMMA_TO_LINEAR_TAB_SIZE + 2];
#define LINEAR_TO_GAMMA_TAB_BITS …
#define LINEAR_TO_GAMMA_TAB_SIZE …
static uint32_t kLinearToGammaTabS[LINEAR_TO_GAMMA_TAB_SIZE + 2];

static const double kGammaF = …;
#define GAMMA_TO_LINEAR_BITS …

static volatile int kGammaTablesSOk = …;
void SharpYuvInitGammaTables(void) { … }

static WEBP_INLINE int Shift(int v, int shift) { … }

static WEBP_INLINE uint32_t FixedPointInterpolation(int v, uint32_t* tab,
                                                    int tab_pos_shift_right,
                                                    int tab_value_shift) { … }

static uint32_t ToLinearSrgb(uint16_t v, int bit_depth) { … }

static uint16_t FromLinearSrgb(uint32_t value, int bit_depth) { … }

////////////////////////////////////////////////////////////////////////////////

#define CLAMP(x, low, high) …
#define MIN(a, b) …
#define MAX(a, b) …

static WEBP_INLINE float Roundf(float x) { … }

static WEBP_INLINE float Powf(float base, float exp) { … }

static WEBP_INLINE float Log10f(float x) { … }

static float ToLinear709(float gamma) { … }

static float FromLinear709(float linear) { … }

static float ToLinear470M(float gamma) { … }

static float FromLinear470M(float linear) { … }

static float ToLinear470Bg(float gamma) { … }

static float FromLinear470Bg(float linear) { … }

static float ToLinearSmpte240(float gamma) { … }

static float FromLinearSmpte240(float linear) { … }

static float ToLinearLog100(float gamma) { … }

static float FromLinearLog100(float linear) { … }

static float ToLinearLog100Sqrt10(float gamma) { … }

static float FromLinearLog100Sqrt10(float linear) { … }

static float ToLinearIec61966(float gamma) { … }

static float FromLinearIec61966(float linear) { … }

static float ToLinearBt1361(float gamma) { … }

static float FromLinearBt1361(float linear) { … }

static float ToLinearPq(float gamma) { … }

static float FromLinearPq(float linear) { … }

static float ToLinearSmpte428(float gamma) { … }

static float FromLinearSmpte428(float linear) { … }

// Conversion in BT.2100 requires RGB info. Simplify to gamma correction here.
static float ToLinearHlg(float gamma) { … }

static float FromLinearHlg(float linear) { … }

uint32_t SharpYuvGammaToLinear(uint16_t v, int bit_depth,
                               SharpYuvTransferFunctionType transfer_type) { … }

uint16_t SharpYuvLinearToGamma(uint32_t v, int bit_depth,
                               SharpYuvTransferFunctionType transfer_type) { … }