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

// Copyright 2010 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.
// -----------------------------------------------------------------------------
//
// inline YUV<->RGB conversion function
//
// The exact naming is Y'CbCr, following the ITU-R BT.601 standard.
// More information at: https://en.wikipedia.org/wiki/YCbCr
// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16
// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128
// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128
// We use 16bit fixed point operations for RGB->YUV conversion (YUV_FIX).
//
// For the Y'CbCr to RGB conversion, the BT.601 specification reads:
//   R = 1.164 * (Y-16) + 1.596 * (V-128)
//   G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128)
//   B = 1.164 * (Y-16)                   + 2.018 * (U-128)
// where Y is in the [16,235] range, and U/V in the [16,240] range.
//
// The fixed-point implementation used here is:
//  R = (19077 . y             + 26149 . v - 14234) >> 6
//  G = (19077 . y -  6419 . u - 13320 . v +  8708) >> 6
//  B = (19077 . y + 33050 . u             - 17685) >> 6
// where the '.' operator is the mulhi_epu16 variant:
//   a . b = ((a << 8) * b) >> 16
// that preserves 8 bits of fractional precision before final descaling.

// Author: Skal ([email protected])

#ifndef WEBP_DSP_YUV_H_
#define WEBP_DSP_YUV_H_

#include "src/dsp/dsp.h"
#include "src/dec/vp8_dec.h"

//------------------------------------------------------------------------------
// YUV -> RGB conversion

#ifdef __cplusplus
extern "C" {
#endif

enum { … };

//------------------------------------------------------------------------------
// slower on x86 by ~7-8%, but bit-exact with the SSE2/NEON version

static WEBP_INLINE int MultHi(int v, int coeff) { … }

static WEBP_INLINE int VP8Clip8(int v) { … }

static WEBP_INLINE int VP8YUVToR(int y, int v) { … }

static WEBP_INLINE int VP8YUVToG(int y, int u, int v) { … }

static WEBP_INLINE int VP8YUVToB(int y, int u) { … }

static WEBP_INLINE void VP8YuvToRgb(int y, int u, int v,
                                    uint8_t* const rgb) { … }

static WEBP_INLINE void VP8YuvToBgr(int y, int u, int v,
                                    uint8_t* const bgr) { … }

static WEBP_INLINE void VP8YuvToRgb565(int y, int u, int v,
                                       uint8_t* const rgb) { … }

static WEBP_INLINE void VP8YuvToRgba4444(int y, int u, int v,
                                         uint8_t* const argb) { … }

//-----------------------------------------------------------------------------
// Alpha handling variants

static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
                                     uint8_t* const argb) { … }

static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,
                                     uint8_t* const bgra) { … }

static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
                                     uint8_t* const rgba) { … }

//-----------------------------------------------------------------------------
// SSE2 extra functions (mostly for upsampling_sse2.c)

#if defined(WEBP_USE_SSE2)

// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
void VP8YuvToRgba32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                         uint8_t* dst);
void VP8YuvToRgb32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                        uint8_t* dst);
void VP8YuvToBgra32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                         uint8_t* dst);
void VP8YuvToBgr32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                        uint8_t* dst);
void VP8YuvToArgb32_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                         uint8_t* dst);
void VP8YuvToRgba444432_SSE2(const uint8_t* y, const uint8_t* u,
                             const uint8_t* v, uint8_t* dst);
void VP8YuvToRgb56532_SSE2(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                           uint8_t* dst);

#endif    // WEBP_USE_SSE2

//-----------------------------------------------------------------------------
// SSE41 extra functions (mostly for upsampling_sse41.c)

#if defined(WEBP_USE_SSE41)

// Process 32 pixels and store the result (16b, 24b or 32b per pixel) in *dst.
void VP8YuvToRgb32_SSE41(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                         uint8_t* dst);
void VP8YuvToBgr32_SSE41(const uint8_t* y, const uint8_t* u, const uint8_t* v,
                         uint8_t* dst);

#endif    // WEBP_USE_SSE41

//------------------------------------------------------------------------------
// RGB -> YUV conversion

// Stub functions that can be called with various rounding values:
static WEBP_INLINE int VP8ClipUV(int uv, int rounding) { … }

static WEBP_INLINE int VP8RGBToY(int r, int g, int b, int rounding) { … }

static WEBP_INLINE int VP8RGBToU(int r, int g, int b, int rounding) { … }

static WEBP_INLINE int VP8RGBToV(int r, int g, int b, int rounding) { … }

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

#endif  // WEBP_DSP_YUV_H_