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 0
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 y, u and v values are divided by 1<<16 and rounded.
73typedef struct {
74 int rgb_to_y[4];
75 int rgb_to_u[4];
76 int rgb_to_v[4];
77} SharpYuvConversionMatrix;
78
79typedef struct SharpYuvOptions SharpYuvOptions;
80
81// Enums for transfer functions, as defined in H.273,
82// https://www.itu.int/rec/T-REC-H.273-202107-I/en
83typedef enum SharpYuvTransferFunctionType {
84 // 0 is reserved
85 kSharpYuvTransferFunctionBt709 = 1,
86 // 2 is unspecified
87 // 3 is reserved
88 kSharpYuvTransferFunctionBt470M = 4,
89 kSharpYuvTransferFunctionBt470Bg = 5,
90 kSharpYuvTransferFunctionBt601 = 6,
91 kSharpYuvTransferFunctionSmpte240 = 7,
92 kSharpYuvTransferFunctionLinear = 8,
93 kSharpYuvTransferFunctionLog100 = 9,
94 kSharpYuvTransferFunctionLog100_Sqrt10 = 10,
95 kSharpYuvTransferFunctionIec61966 = 11,
96 kSharpYuvTransferFunctionBt1361 = 12,
97 kSharpYuvTransferFunctionSrgb = 13,
98 kSharpYuvTransferFunctionBt2020_10Bit = 14,
99 kSharpYuvTransferFunctionBt2020_12Bit = 15,
100 kSharpYuvTransferFunctionSmpte2084 = 16, // PQ
101 kSharpYuvTransferFunctionSmpte428 = 17,
102 kSharpYuvTransferFunctionHlg = 18,
103 kSharpYuvTransferFunctionNum
104} SharpYuvTransferFunctionType;
105
106// Converts RGB to YUV420 using a downsampling algorithm that minimizes
107// artefacts caused by chroma subsampling.
108// This is slower than standard downsampling (averaging of 4 UV values).
109// Assumes that the image will be upsampled using a bilinear filter. If nearest
110// neighbor is used instead, the upsampled image might look worse than with
111// standard downsampling.
112// r_ptr, g_ptr, b_ptr: pointers to the source r, g and b channels. Should point
113// to uint8_t buffers if rgb_bit_depth is 8, or uint16_t buffers otherwise.
114// rgb_step: distance in bytes between two horizontally adjacent pixels on the
115// r, g and b channels. If rgb_bit_depth is > 8, it should be a
116// multiple of 2.
117// rgb_stride: distance in bytes between two vertically adjacent pixels on the
118// r, g, and b channels. If rgb_bit_depth is > 8, it should be a
119// multiple of 2.
120// rgb_bit_depth: number of bits for each r/g/b value. One of: 8, 10, 12, 16.
121// Note: 16 bit input is truncated to 14 bits before conversion to yuv.
122// yuv_bit_depth: number of bits for each y/u/v value. One of: 8, 10, 12.
123// y_ptr, u_ptr, v_ptr: pointers to the destination y, u and v channels. Should
124// point to uint8_t buffers if yuv_bit_depth is 8, or uint16_t buffers
125// otherwise.
126// y_stride, u_stride, v_stride: distance in bytes between two vertically
127// adjacent pixels on the y, u and v channels. If yuv_bit_depth > 8, they
128// should be multiples of 2.
129// width, height: width and height of the image in pixels
130// This function calls SharpYuvConvertWithOptions with a default transfer
131// function of kSharpYuvTransferFunctionSrgb.
132SHARPYUV_EXTERN int SharpYuvConvert(const void* r_ptr, const void* g_ptr,
133 const void* b_ptr, int rgb_step,
134 int rgb_stride, int rgb_bit_depth,
135 void* y_ptr, int y_stride, void* u_ptr,
136 int u_stride, void* v_ptr, int v_stride,
137 int yuv_bit_depth, int width, int height,
138 const SharpYuvConversionMatrix* yuv_matrix);
139
140struct SharpYuvOptions {
141 // This matrix cannot be NULL and can be initialized by
142 // SharpYuvComputeConversionMatrix.
143 const SharpYuvConversionMatrix* yuv_matrix;
144 SharpYuvTransferFunctionType transfer_type;
145};
146
147// Internal, version-checked, entry point
148SHARPYUV_EXTERN int SharpYuvOptionsInitInternal(const SharpYuvConversionMatrix*,
149 SharpYuvOptions*, int);
150
151// Should always be called, to initialize a fresh SharpYuvOptions
152// structure before modification. SharpYuvOptionsInit() must have succeeded
153// before using the 'options' object.
154static SHARPYUV_INLINE int SharpYuvOptionsInit(
155 const SharpYuvConversionMatrix* yuv_matrix, SharpYuvOptions* options) {
156 return SharpYuvOptionsInitInternal(yuv_matrix, options, SHARPYUV_VERSION);
157}
158
159SHARPYUV_EXTERN int SharpYuvConvertWithOptions(
160 const void* r_ptr, const void* g_ptr, const void* b_ptr, int rgb_step,
161 int rgb_stride, int rgb_bit_depth, void* y_ptr, int y_stride, void* u_ptr,
162 int u_stride, void* v_ptr, int v_stride, int yuv_bit_depth, int width,
163 int height, const SharpYuvOptions* options);
164
165// TODO(b/194336375): Add YUV444 to YUV420 conversion. Maybe also add 422
166// support (it's rarely used in practice, especially for images).
167
168#ifdef __cplusplus
169} // extern "C"
170#endif
171
172#endif // WEBP_SHARPYUV_SHARPYUV_H_
173

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