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Diffstat (limited to 'media/libwebp/sharpyuv/sharpyuv.h')
| -rw-r--r-- | media/libwebp/sharpyuv/sharpyuv.h | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/media/libwebp/sharpyuv/sharpyuv.h b/media/libwebp/sharpyuv/sharpyuv.h new file mode 100644 index 0000000000..9386ea2185 --- /dev/null +++ b/media/libwebp/sharpyuv/sharpyuv.h @@ -0,0 +1,81 @@ +// 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. +// ----------------------------------------------------------------------------- +// +// Sharp RGB to YUV conversion. + +#ifndef WEBP_SHARPYUV_SHARPYUV_H_ +#define WEBP_SHARPYUV_SHARPYUV_H_ + +#include <inttypes.h> + +#ifdef __cplusplus +extern "C" { +#endif + +// SharpYUV API version following the convention from semver.org +#define SHARPYUV_VERSION_MAJOR 0 +#define SHARPYUV_VERSION_MINOR 1 +#define SHARPYUV_VERSION_PATCH 0 +// Version as a uint32_t. The major number is the high 8 bits. +// The minor number is the middle 8 bits. The patch number is the low 16 bits. +#define SHARPYUV_MAKE_VERSION(MAJOR, MINOR, PATCH) \ + (((MAJOR) << 24) | ((MINOR) << 16) | (PATCH)) +#define SHARPYUV_VERSION \ + SHARPYUV_MAKE_VERSION(SHARPYUV_VERSION_MAJOR, SHARPYUV_VERSION_MINOR, \ + SHARPYUV_VERSION_PATCH) + +// RGB to YUV conversion matrix, in 16 bit fixed point. +// y = rgb_to_y[0] * r + rgb_to_y[1] * g + rgb_to_y[2] * b + rgb_to_y[3] +// u = rgb_to_u[0] * r + rgb_to_u[1] * g + rgb_to_u[2] * b + rgb_to_u[3] +// v = rgb_to_v[0] * r + rgb_to_v[1] * g + rgb_to_v[2] * b + rgb_to_v[3] +// Then y, u and v values are divided by 1<<16 and rounded. +typedef struct { + int rgb_to_y[4]; + int rgb_to_u[4]; + int rgb_to_v[4]; +} SharpYuvConversionMatrix; + +// Converts RGB to YUV420 using a downsampling algorithm that minimizes +// artefacts caused by chroma subsampling. +// This is slower than standard downsampling (averaging of 4 UV values). +// Assumes that the image will be upsampled using a bilinear filter. If nearest +// neighbor is used instead, the upsampled image might look worse than with +// standard downsampling. +// r_ptr, g_ptr, b_ptr: pointers to the source r, g and b channels. Should point +// to uint8_t buffers if rgb_bit_depth is 8, or uint16_t buffers otherwise. +// rgb_step: distance in bytes between two horizontally adjacent pixels on the +// r, g and b channels. If rgb_bit_depth is > 8, it should be a +// multiple of 2. +// rgb_stride: distance in bytes between two vertically adjacent pixels on the +// r, g, and b channels. If rgb_bit_depth is > 8, it should be a +// multiple of 2. +// rgb_bit_depth: number of bits for each r/g/b value. One of: 8, 10, 12, 16. +// Note: 16 bit input is truncated to 14 bits before conversion to yuv. +// yuv_bit_depth: number of bits for each y/u/v value. One of: 8, 10, 12. +// y_ptr, u_ptr, v_ptr: pointers to the destination y, u and v channels. Should +// point to uint8_t buffers if yuv_bit_depth is 8, or uint16_t buffers +// otherwise. +// y_stride, u_stride, v_stride: distance in bytes between two vertically +// adjacent pixels on the y, u and v channels. If yuv_bit_depth > 8, they +// should be multiples of 2. +// width, height: width and height of the image in pixels +int SharpYuvConvert(const void* r_ptr, const void* g_ptr, const void* b_ptr, + int rgb_step, int rgb_stride, int rgb_bit_depth, + void* y_ptr, int y_stride, void* u_ptr, int u_stride, + void* v_ptr, int v_stride, int yuv_bit_depth, int width, + int height, const SharpYuvConversionMatrix* yuv_matrix); + +// TODO(b/194336375): Add YUV444 to YUV420 conversion. Maybe also add 422 +// support (it's rarely used in practice, especially for images). + +#ifdef __cplusplus +} // extern "C" +#endif + +#endif // WEBP_SHARPYUV_SHARPYUV_H_ |