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https://github.com/webmproject/libwebp.git
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182 lines
7.5 KiB
C
182 lines
7.5 KiB
C
// Copyright 2022 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Sharp RGB to YUV conversion.
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#ifndef WEBP_SHARPYUV_SHARPYUV_H_
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#define WEBP_SHARPYUV_SHARPYUV_H_
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifndef SHARPYUV_EXTERN
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#ifdef WEBP_EXTERN
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#define SHARPYUV_EXTERN WEBP_EXTERN
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#else
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// This explicitly marks library functions and allows for changing the
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// signature for e.g., Windows DLL builds.
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#if defined(_WIN32) && defined(WEBP_DLL)
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#define SHARPYUV_EXTERN __declspec(dllexport)
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#elif defined(__GNUC__) && __GNUC__ >= 4
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#define SHARPYUV_EXTERN extern __attribute__((visibility("default")))
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#else
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#define SHARPYUV_EXTERN extern
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#endif /* defined(_WIN32) && defined(WEBP_DLL) */
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#endif /* WEBP_EXTERN */
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#endif /* SHARPYUV_EXTERN */
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#ifndef SHARPYUV_INLINE
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#ifdef WEBP_INLINE
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#define SHARPYUV_INLINE WEBP_INLINE
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#else
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#ifndef _MSC_VER
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#if defined(__cplusplus) || !defined(__STRICT_ANSI__) || \
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(defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L)
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#define SHARPYUV_INLINE inline
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#else
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#define SHARPYUV_INLINE
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#endif
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#else
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#define SHARPYUV_INLINE __forceinline
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#endif /* _MSC_VER */
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#endif /* WEBP_INLINE */
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#endif /* SHARPYUV_INLINE */
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// SharpYUV API version following the convention from semver.org
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#define SHARPYUV_VERSION_MAJOR 0
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#define SHARPYUV_VERSION_MINOR 4
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#define SHARPYUV_VERSION_PATCH 0
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// Version as a uint32_t. The major number is the high 8 bits.
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// The minor number is the middle 8 bits. The patch number is the low 16 bits.
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#define SHARPYUV_MAKE_VERSION(MAJOR, MINOR, PATCH) \
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(((MAJOR) << 24) | ((MINOR) << 16) | (PATCH))
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#define SHARPYUV_VERSION \
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SHARPYUV_MAKE_VERSION(SHARPYUV_VERSION_MAJOR, SHARPYUV_VERSION_MINOR, \
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SHARPYUV_VERSION_PATCH)
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// Returns the library's version number, packed in hexadecimal. See
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// SHARPYUV_VERSION.
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SHARPYUV_EXTERN int SharpYuvGetVersion(void);
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// RGB to YUV conversion matrix, in 16 bit fixed point.
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// y_ = rgb_to_y[0] * r + rgb_to_y[1] * g + rgb_to_y[2] * b + rgb_to_y[3]
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// u_ = rgb_to_u[0] * r + rgb_to_u[1] * g + rgb_to_u[2] * b + rgb_to_u[3]
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// v_ = rgb_to_v[0] * r + rgb_to_v[1] * g + rgb_to_v[2] * b + rgb_to_v[3]
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// Then the values are divided by 1<<16 and rounded.
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// y = (y_ + (1 << 15)) >> 16
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// u = (u_ + (1 << 15)) >> 16
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// v = (v_ + (1 << 15)) >> 16
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//
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// Typically, the offset values rgb_to_y[3], rgb_to_u[3] and rgb_to_v[3] depend
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// on the input's bit depth, e.g., rgb_to_u[3] = 1 << (rgb_bit_depth - 1 + 16).
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// See also sharpyuv_csp.h to get a predefined matrix or generate a matrix.
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typedef struct {
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int rgb_to_y[4];
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int rgb_to_u[4];
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int rgb_to_v[4];
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} SharpYuvConversionMatrix;
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typedef struct SharpYuvOptions SharpYuvOptions;
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// Enums for transfer functions, as defined in H.273,
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// https://www.itu.int/rec/T-REC-H.273-202107-I/en
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typedef enum SharpYuvTransferFunctionType {
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// 0 is reserved
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kSharpYuvTransferFunctionBt709 = 1,
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// 2 is unspecified
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// 3 is reserved
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kSharpYuvTransferFunctionBt470M = 4,
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kSharpYuvTransferFunctionBt470Bg = 5,
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kSharpYuvTransferFunctionBt601 = 6,
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kSharpYuvTransferFunctionSmpte240 = 7,
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kSharpYuvTransferFunctionLinear = 8,
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kSharpYuvTransferFunctionLog100 = 9,
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kSharpYuvTransferFunctionLog100_Sqrt10 = 10,
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kSharpYuvTransferFunctionIec61966 = 11,
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kSharpYuvTransferFunctionBt1361 = 12,
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kSharpYuvTransferFunctionSrgb = 13,
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kSharpYuvTransferFunctionBt2020_10Bit = 14,
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kSharpYuvTransferFunctionBt2020_12Bit = 15,
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kSharpYuvTransferFunctionSmpte2084 = 16, // PQ
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kSharpYuvTransferFunctionSmpte428 = 17,
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kSharpYuvTransferFunctionHlg = 18,
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kSharpYuvTransferFunctionNum
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} SharpYuvTransferFunctionType;
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// Converts RGB to YUV420 using a downsampling algorithm that minimizes
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// artefacts caused by chroma subsampling.
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// This is slower than standard downsampling (averaging of 4 UV values).
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// Assumes that the image will be upsampled using a bilinear filter. If nearest
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// neighbor is used instead, the upsampled image might look worse than with
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// standard downsampling.
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// r_ptr, g_ptr, b_ptr: pointers to the source r, g and b channels. Should point
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// to uint8_t buffers if rgb_bit_depth is 8, or uint16_t buffers otherwise.
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// rgb_step: distance in bytes between two horizontally adjacent pixels on the
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// r, g and b channels. If rgb_bit_depth is > 8, it should be a
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// multiple of 2.
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// rgb_stride: distance in bytes between two vertically adjacent pixels on the
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// r, g, and b channels. If rgb_bit_depth is > 8, it should be a
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// multiple of 2.
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// rgb_bit_depth: number of bits for each r/g/b value. One of: 8, 10, 12, 16.
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// Note: 16 bit input is truncated to 14 bits before conversion to yuv.
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// yuv_bit_depth: number of bits for each y/u/v value. One of: 8, 10, 12.
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// y_ptr, u_ptr, v_ptr: pointers to the destination y, u and v channels. Should
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// point to uint8_t buffers if yuv_bit_depth is 8, or uint16_t buffers
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// otherwise.
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// y_stride, u_stride, v_stride: distance in bytes between two vertically
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// adjacent pixels on the y, u and v channels. If yuv_bit_depth > 8, they
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// should be multiples of 2.
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// width, height: width and height of the image in pixels
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// yuv_matrix: RGB to YUV conversion matrix. The matrix values typically
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// depend on the input's rgb_bit_depth.
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// This function calls SharpYuvConvertWithOptions with a default transfer
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// function of kSharpYuvTransferFunctionSrgb.
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SHARPYUV_EXTERN int SharpYuvConvert(const void* r_ptr, const void* g_ptr,
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const void* b_ptr, int rgb_step,
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int rgb_stride, int rgb_bit_depth,
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void* y_ptr, int y_stride, void* u_ptr,
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int u_stride, void* v_ptr, int v_stride,
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int yuv_bit_depth, int width, int height,
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const SharpYuvConversionMatrix* yuv_matrix);
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struct SharpYuvOptions {
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// This matrix cannot be NULL and can be initialized by
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// SharpYuvComputeConversionMatrix.
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const SharpYuvConversionMatrix* yuv_matrix;
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SharpYuvTransferFunctionType transfer_type;
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};
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// Internal, version-checked, entry point
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SHARPYUV_EXTERN int SharpYuvOptionsInitInternal(const SharpYuvConversionMatrix*,
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SharpYuvOptions*, int);
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// Should always be called, to initialize a fresh SharpYuvOptions
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// structure before modification. SharpYuvOptionsInit() must have succeeded
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// before using the 'options' object.
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static SHARPYUV_INLINE int SharpYuvOptionsInit(
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const SharpYuvConversionMatrix* yuv_matrix, SharpYuvOptions* options) {
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return SharpYuvOptionsInitInternal(yuv_matrix, options, SHARPYUV_VERSION);
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}
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SHARPYUV_EXTERN int SharpYuvConvertWithOptions(
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const void* r_ptr, const void* g_ptr, const void* b_ptr, int rgb_step,
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int rgb_stride, int rgb_bit_depth, void* y_ptr, int y_stride, void* u_ptr,
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int u_stride, void* v_ptr, int v_stride, int yuv_bit_depth, int width,
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int height, const SharpYuvOptions* options);
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// TODO(b/194336375): Add YUV444 to YUV420 conversion. Maybe also add 422
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// support (it's rarely used in practice, especially for images).
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif // WEBP_SHARPYUV_SHARPYUV_H_
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