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112 lines
3.6 KiB
C
112 lines
3.6 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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// Colorspace utilities.
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#include "sharpyuv/sharpyuv_csp.h"
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#include <assert.h>
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#include <math.h>
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#include <string.h>
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static int ToFixed16(float f) { return (int)round(f * (1 << 16)); }
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void SharpYuvComputeConversionMatrix(const SharpYuvColorSpace* yuv_color_space,
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SharpYuvConversionMatrix* matrix) {
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const float kr = yuv_color_space->kr;
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const float kb = yuv_color_space->kb;
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const float kg = 1.0f - kr - kb;
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const float cr = 0.5f / (1.0f - kb);
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const float cb = 0.5f / (1.0f - kr);
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const int shift = yuv_color_space->bits - 8;
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const float denom = (float)((1 << yuv_color_space->bits) - 1);
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float scaleY = 1.0f;
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float addY = 0.0f;
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float scaleU = cr;
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float scaleV = cb;
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float addUV = (128 << shift);
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assert(yuv_color_space->bits >= 8);
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if (yuv_color_space->range == kSharpYuvRangeLimited) {
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scaleY *= (219 << shift) / denom;
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scaleU *= (224 << shift) / denom;
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scaleV *= (224 << shift) / denom;
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addY = (16 << shift);
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}
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matrix->rgb_to_y[0] = ToFixed16(kr * scaleY);
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matrix->rgb_to_y[1] = ToFixed16(kg * scaleY);
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matrix->rgb_to_y[2] = ToFixed16(kb * scaleY);
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matrix->rgb_to_y[3] = ToFixed16(addY);
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matrix->rgb_to_u[0] = ToFixed16(-kr * scaleU);
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matrix->rgb_to_u[1] = ToFixed16(-kg * scaleU);
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matrix->rgb_to_u[2] = ToFixed16((1 - kb) * scaleU);
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matrix->rgb_to_u[3] = ToFixed16(addUV);
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matrix->rgb_to_v[0] = ToFixed16((1 - kr) * scaleV);
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matrix->rgb_to_v[1] = ToFixed16(-kg * scaleV);
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matrix->rgb_to_v[2] = ToFixed16(-kb * scaleV);
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matrix->rgb_to_v[3] = ToFixed16(addUV);
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}
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// Matrices are in YUV_FIX fixed point precision.
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// WebP's matrix, similar but not identical to kRec601LimitedMatrix.
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static const SharpYuvConversionMatrix kWebpMatrix = {
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{16839, 33059, 6420, 16 << 16},
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{-9719, -19081, 28800, 128 << 16},
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{28800, -24116, -4684, 128 << 16},
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};
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// Kr=0.2990f Kb=0.1140f btits=8 range=kLimited
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static const SharpYuvConversionMatrix kRec601LimitedMatrix = {
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{16829, 33039, 6416, 16 << 16},
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{-9714, -19071, 28784, 128 << 16},
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{28784, -24103, -4681, 128 << 16},
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};
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// Kr=0.2990f Kb=0.1140f btits=8 range=kFull
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static const SharpYuvConversionMatrix kRec601FullMatrix = {
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{19595, 38470, 7471, 0},
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{-11058, -21710, 32768, 128 << 16},
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{32768, -27439, -5329, 128 << 16},
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};
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// Kr=0.2126f Kb=0.0722f bits=8 range=kLimited
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static const SharpYuvConversionMatrix kRec709LimitedMatrix = {
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{11966, 40254, 4064, 16 << 16},
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{-6596, -22189, 28784, 128 << 16},
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{28784, -26145, -2639, 128 << 16},
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};
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// Kr=0.2126f Kb=0.0722f bits=8 range=kFull
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static const SharpYuvConversionMatrix kRec709FullMatrix = {
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{13933, 46871, 4732, 0},
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{-7509, -25259, 32768, 128 << 16},
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{32768, -29763, -3005, 128 << 16},
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};
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const SharpYuvConversionMatrix* SharpYuvGetConversionMatrix(
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SharpYuvMatrixType matrix_type) {
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switch (matrix_type) {
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case kSharpYuvMatrixWebp:
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return &kWebpMatrix;
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case kSharpYuvMarixRec601Limited:
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return &kRec601LimitedMatrix;
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case kSharpYuvMarixRec601Full:
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return &kRec601FullMatrix;
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case kSharpYuvMarixRec709Limited:
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return &kRec709LimitedMatrix;
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case kSharpYuvMarixRec709Full:
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return &kRec709FullMatrix;
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case kSharpYuvMarixNum:
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return NULL;
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}
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return NULL;
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}
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