1// Copyright 2022 Google Inc. All Rights Reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the COPYING file in the root of the source
5// tree. An additional intellectual property rights grant can be found
6// in the file PATENTS. All contributing project authors may
7// be found in the AUTHORS file in the root of the source tree.
8// -----------------------------------------------------------------------------
9//
10// Sharp RGB to YUV conversion.
11
12#ifndef WEBP_SHARPYUV_SHARPYUV_H_
13#define WEBP_SHARPYUV_SHARPYUV_H_
14
15#ifdef __cplusplus
16extern "C" {
17#endif
18
19#ifndef SHARPYUV_EXTERN
20#ifdef WEBP_EXTERN
21#define SHARPYUV_EXTERN WEBP_EXTERN
22#else
23// This explicitly marks library functions and allows for changing the
24// signature for e.g., Windows DLL builds.
25#if defined(_WIN32) && defined(WEBP_DLL)
26#define SHARPYUV_EXTERN __declspec(dllexport)
27#elif defined(__GNUC__) && __GNUC__ >= 4
28#define SHARPYUV_EXTERN extern __attribute__((visibility("default")))
29#else
30#define SHARPYUV_EXTERN extern
31#endif /* defined(_WIN32) && defined(WEBP_DLL) */
32#endif /* WEBP_EXTERN */
33#endif /* SHARPYUV_EXTERN */
34
35#ifndef SHARPYUV_INLINE
36#ifdef WEBP_INLINE
37#define SHARPYUV_INLINE WEBP_INLINE
38#else
39#ifndef _MSC_VER
40#if defined(__cplusplus) || !defined(__STRICT_ANSI__) || \
41 (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L)
42#define SHARPYUV_INLINE inline
43#else
44#define SHARPYUV_INLINE
45#endif
46#else
47#define SHARPYUV_INLINE __forceinline
48#endif /* _MSC_VER */
49#endif /* WEBP_INLINE */
50#endif /* SHARPYUV_INLINE */
51
52// SharpYUV API version following the convention from semver.org
53#define SHARPYUV_VERSION_MAJOR 0
54#define SHARPYUV_VERSION_MINOR 4
55#define SHARPYUV_VERSION_PATCH 1
56// Version as a uint32_t. The major number is the high 8 bits.
57// The minor number is the middle 8 bits. The patch number is the low 16 bits.
58#define SHARPYUV_MAKE_VERSION(MAJOR, MINOR, PATCH) \
59 (((MAJOR) << 24) | ((MINOR) << 16) | (PATCH))
60#define SHARPYUV_VERSION \
61 SHARPYUV_MAKE_VERSION(SHARPYUV_VERSION_MAJOR, SHARPYUV_VERSION_MINOR, \
62 SHARPYUV_VERSION_PATCH)
63
64// Returns the library's version number, packed in hexadecimal. See
65// SHARPYUV_VERSION.
66SHARPYUV_EXTERN int SharpYuvGetVersion(void);
67
68// RGB to YUV conversion matrix, in 16 bit fixed point.
69// y_ = rgb_to_y[0] * r + rgb_to_y[1] * g + rgb_to_y[2] * b + rgb_to_y[3]
70// u_ = rgb_to_u[0] * r + rgb_to_u[1] * g + rgb_to_u[2] * b + rgb_to_u[3]
71// v_ = rgb_to_v[0] * r + rgb_to_v[1] * g + rgb_to_v[2] * b + rgb_to_v[3]
72// Then the values are divided by 1<<16 and rounded.
73// y = (y_ + (1 << 15)) >> 16
74// u = (u_ + (1 << 15)) >> 16
75// v = (v_ + (1 << 15)) >> 16
76//
77// Typically, the offset values rgb_to_y[3], rgb_to_u[3] and rgb_to_v[3] depend
78// on the input's bit depth, e.g., rgb_to_u[3] = 1 << (rgb_bit_depth - 1 + 16).
79// See also sharpyuv_csp.h to get a predefined matrix or generate a matrix.
80typedef struct {
81 int rgb_to_y[4];
82 int rgb_to_u[4];
83 int rgb_to_v[4];
84} SharpYuvConversionMatrix;
85
86typedef struct SharpYuvOptions SharpYuvOptions;
87
88// Enums for transfer functions, as defined in H.273,
89// https://www.itu.int/rec/T-REC-H.273-202107-I/en
90typedef enum SharpYuvTransferFunctionType {
91 // 0 is reserved
92 kSharpYuvTransferFunctionBt709 = 1,
93 // 2 is unspecified
94 // 3 is reserved
95 kSharpYuvTransferFunctionBt470M = 4,
96 kSharpYuvTransferFunctionBt470Bg = 5,
97 kSharpYuvTransferFunctionBt601 = 6,
98 kSharpYuvTransferFunctionSmpte240 = 7,
99 kSharpYuvTransferFunctionLinear = 8,
100 kSharpYuvTransferFunctionLog100 = 9,
101 kSharpYuvTransferFunctionLog100_Sqrt10 = 10,
102 kSharpYuvTransferFunctionIec61966 = 11,
103 kSharpYuvTransferFunctionBt1361 = 12,
104 kSharpYuvTransferFunctionSrgb = 13,
105 kSharpYuvTransferFunctionBt2020_10Bit = 14,
106 kSharpYuvTransferFunctionBt2020_12Bit = 15,
107 kSharpYuvTransferFunctionSmpte2084 = 16, // PQ
108 kSharpYuvTransferFunctionSmpte428 = 17,
109 kSharpYuvTransferFunctionHlg = 18,
110 kSharpYuvTransferFunctionNum
111} SharpYuvTransferFunctionType;
112
113// Converts RGB to YUV420 using a downsampling algorithm that minimizes
114// artefacts caused by chroma subsampling.
115// This is slower than standard downsampling (averaging of 4 UV values).
116// Assumes that the image will be upsampled using a bilinear filter. If nearest
117// neighbor is used instead, the upsampled image might look worse than with
118// standard downsampling.
119// r_ptr, g_ptr, b_ptr: pointers to the source r, g and b channels. Should point
120// to uint8_t buffers if rgb_bit_depth is 8, or uint16_t buffers otherwise.
121// rgb_step: distance in bytes between two horizontally adjacent pixels on the
122// r, g and b channels. If rgb_bit_depth is > 8, it should be a
123// multiple of 2.
124// rgb_stride: distance in bytes between two vertically adjacent pixels on the
125// r, g, and b channels. If rgb_bit_depth is > 8, it should be a
126// multiple of 2.
127// rgb_bit_depth: number of bits for each r/g/b value. One of: 8, 10, 12, 16.
128// Note: 16 bit input is truncated to 14 bits before conversion to yuv.
129// yuv_bit_depth: number of bits for each y/u/v value. One of: 8, 10, 12.
130// y_ptr, u_ptr, v_ptr: pointers to the destination y, u and v channels. Should
131// point to uint8_t buffers if yuv_bit_depth is 8, or uint16_t buffers
132// otherwise.
133// y_stride, u_stride, v_stride: distance in bytes between two vertically
134// adjacent pixels on the y, u and v channels. If yuv_bit_depth > 8, they
135// should be multiples of 2.
136// width, height: width and height of the image in pixels
137// yuv_matrix: RGB to YUV conversion matrix. The matrix values typically
138// depend on the input's rgb_bit_depth.
139// This function calls SharpYuvConvertWithOptions with a default transfer
140// function of kSharpYuvTransferFunctionSrgb.
141SHARPYUV_EXTERN int SharpYuvConvert(const void* r_ptr, const void* g_ptr,
142 const void* b_ptr, int rgb_step,
143 int rgb_stride, int rgb_bit_depth,
144 void* y_ptr, int y_stride, void* u_ptr,
145 int u_stride, void* v_ptr, int v_stride,
146 int yuv_bit_depth, int width, int height,
147 const SharpYuvConversionMatrix* yuv_matrix);
148
149struct SharpYuvOptions {
150 // This matrix cannot be NULL and can be initialized by
151 // SharpYuvComputeConversionMatrix.
152 const SharpYuvConversionMatrix* yuv_matrix;
153 SharpYuvTransferFunctionType transfer_type;
154};
155
156// Internal, version-checked, entry point
157SHARPYUV_EXTERN int SharpYuvOptionsInitInternal(const SharpYuvConversionMatrix*,
158 SharpYuvOptions*, int);
159
160// Should always be called, to initialize a fresh SharpYuvOptions
161// structure before modification. SharpYuvOptionsInit() must have succeeded
162// before using the 'options' object.
163static SHARPYUV_INLINE int SharpYuvOptionsInit(
164 const SharpYuvConversionMatrix* yuv_matrix, SharpYuvOptions* options) {
165 return SharpYuvOptionsInitInternal(yuv_matrix, options, SHARPYUV_VERSION);
166}
167
168SHARPYUV_EXTERN int SharpYuvConvertWithOptions(
169 const void* r_ptr, const void* g_ptr, const void* b_ptr, int rgb_step,
170 int rgb_stride, int rgb_bit_depth, void* y_ptr, int y_stride, void* u_ptr,
171 int u_stride, void* v_ptr, int v_stride, int yuv_bit_depth, int width,
172 int height, const SharpYuvOptions* options);
173
174// TODO(b/194336375): Add YUV444 to YUV420 conversion. Maybe also add 422
175// support (it's rarely used in practice, especially for images).
176
177#ifdef __cplusplus
178} // extern "C"
179#endif
180
181#endif // WEBP_SHARPYUV_SHARPYUV_H_
182

source code of qtimageformats/src/3rdparty/libwebp/sharpyuv/sharpyuv.h