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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/354829279): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "ui/gfx/skia_color_space_util.h"
#include <algorithm>
#include <cmath>
#include <vector>
#include "base/check.h"
namespace gfx {
float SkTransferFnEvalUnclamped(const skcms_TransferFunction& fn, float x) {
if (x < fn.d)
return fn.c * x + fn.f;
return std::pow(fn.a * x + fn.b, fn.g) + fn.e;
}
namespace {
float SkTransferFnEval(const skcms_TransferFunction& fn, float x) {
float fn_at_x_unclamped = SkTransferFnEvalUnclamped(fn, x);
return std::clamp(fn_at_x_unclamped, 0.0f, 1.0f);
}
} // namespace
skcms_TransferFunction SkTransferFnInverse(const skcms_TransferFunction& fn) {
skcms_TransferFunction fn_inv = {0};
if (fn.a > 0 && fn.g > 0) {
double a_to_the_g = std::pow(fn.a, fn.g);
fn_inv.a = 1.f / a_to_the_g;
fn_inv.b = -fn.e / a_to_the_g;
fn_inv.g = 1.f / fn.g;
}
fn_inv.d = fn.c * fn.d + fn.f;
fn_inv.e = -fn.b / fn.a;
if (fn.c != 0) {
fn_inv.c = 1.f / fn.c;
fn_inv.f = -fn.f / fn.c;
}
return fn_inv;
}
bool SkTransferFnsApproximatelyCancel(const skcms_TransferFunction& a,
const skcms_TransferFunction& b) {
const float kStep = 1.f / 8.f;
const float kEpsilon = 2.5f / 256.f;
for (float x = 0; x <= 1.f; x += kStep) {
float a_of_x = SkTransferFnEval(a, x);
float b_of_a_of_x = SkTransferFnEval(b, a_of_x);
if (std::abs(b_of_a_of_x - x) > kEpsilon)
return false;
}
return true;
}
bool SkTransferFnIsApproximatelyIdentity(const skcms_TransferFunction& a) {
const float kStep = 1.f / 8.f;
const float kEpsilon = 2.5f / 256.f;
for (float x = 0; x <= 1.f; x += kStep) {
float a_of_x = SkTransferFnEval(a, x);
if (std::abs(a_of_x - x) > kEpsilon)
return false;
}
return true;
}
bool SkM44IsApproximatelyIdentity(const SkM44& m, float epsilon) {
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
float identity_value = i == j ? 1 : 0;
float value = m.rc(i, j);
if (std::abs(identity_value - value) > epsilon) {
return false;
}
}
}
return true;
}
skcms_Matrix3x3 COLOR_SPACE_EXPORT SkcmsMatrix3x3FromSkM44(const SkM44& in) {
// clang-format off
return {{
{ in.rc(0, 0), in.rc(0, 1), in.rc(0, 2), },
{ in.rc(1, 0), in.rc(1, 1), in.rc(1, 2), },
{ in.rc(2, 0), in.rc(2, 1), in.rc(2, 2), },
}};
// clang-format on
}
SkM44 COLOR_SPACE_EXPORT SkM44FromSkcmsMatrix3x3(const skcms_Matrix3x3& in) {
return SkM44FromRowMajor3x3(&in.vals[0][0]);
}
SkM44 SkM44FromRowMajor3x3(const float* data) {
DCHECK(data);
// clang-format off
return SkM44(data[0], data[1], data[2], 0,
data[3], data[4], data[5], 0,
data[6], data[7], data[8], 0,
0, 0, 0, 1);
// clang-format on
}
} // namespace gfx
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