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// Copyright (C) 2018 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QCOLORTRANSFERTABLE_P_H
#define QCOLORTRANSFERTABLE_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <QtGui/private/qtguiglobal_p.h>
#include "qcolortransferfunction_p.h"
#include <QList>
#include <algorithm>
#include <cmath>
QT_BEGIN_NAMESPACE
// Defines either an ICC TRC 'curve' or a lut8/lut16 A or B table
class Q_GUI_EXPORT QColorTransferTable
{
public:
QColorTransferTable() noexcept
: m_tableSize(0)
{ }
QColorTransferTable(uint32_t size, const QList<uint8_t> &table) noexcept
: m_tableSize(size), m_table8(table)
{
Q_ASSERT(qsizetype(size) <= table.count());
}
QColorTransferTable(uint32_t size, const QList<uint16_t> &table) noexcept
: m_tableSize(size), m_table16(table)
{
Q_ASSERT(qsizetype(size) <= table.count());
}
bool isEmpty() const
{
return m_tableSize == 0;
}
bool checkValidity() const
{
if (isEmpty())
return true;
// Only one table can be set
if (!m_table8.isEmpty() && !m_table16.isEmpty())
return false;
// At least 2 elements
if (m_tableSize < 2)
return false;
// The table must describe an injective curve:
if (!m_table8.isEmpty()) {
uint8_t val = 0;
for (uint i = 0; i < m_tableSize; ++i) {
if (m_table8[i] < val)
return false;
val = m_table8[i];
}
}
if (!m_table16.isEmpty()) {
uint16_t val = 0;
for (uint i = 0; i < m_tableSize; ++i) {
if (m_table16[i] < val)
return false;
val = m_table16[i];
}
}
return true;
}
float apply(float x) const
{
x = std::clamp(x, 0.0f, 1.0f);
x *= m_tableSize - 1;
const uint32_t lo = static_cast<uint32_t>(std::floor(x));
const uint32_t hi = std::min(lo + 1, m_tableSize - 1);
const float frac = x - lo;
if (!m_table16.isEmpty())
return (m_table16[lo] * (1.0f - frac) + m_table16[hi] * frac) * (1.0f/65535.0f);
if (!m_table8.isEmpty())
return (m_table8[lo] * (1.0f - frac) + m_table8[hi] * frac) * (1.0f/255.0f);
return x;
}
// Apply inverse, optimized by giving a previous result a value < x.
float applyInverse(float x, float resultLargerThan = 0.0f) const
{
Q_ASSERT(resultLargerThan >= 0.0f && resultLargerThan <= 1.0f);
if (x <= 0.0f)
return 0.0f;
if (x >= 1.0f)
return 1.0f;
if (!m_table16.isEmpty()) {
const float v = x * 65535.0f;
uint32_t i = static_cast<uint32_t>(std::floor(resultLargerThan * (m_tableSize - 1)));
auto it = std::lower_bound(m_table16.cbegin() + i, m_table16.cend(), v);
i = it - m_table16.cbegin();
if (i >= m_tableSize - 1)
return 1.0f;
const float y1 = m_table16[i - 1];
const float y2 = m_table16[i];
Q_ASSERT(v >= y1 && v <= y2);
const float fr = (v - y1) / (y2 - y1);
return (i + fr) * (1.0f / (m_tableSize - 1));
}
if (!m_table8.isEmpty()) {
const float v = x * 255.0f;
uint32_t i = static_cast<uint32_t>(std::floor(resultLargerThan * (m_tableSize - 1)));
auto it = std::lower_bound(m_table8.cbegin() + i, m_table8.cend(), v);
i = it - m_table8.cbegin();
if (i >= m_tableSize - 1)
return 1.0f;
const float y1 = m_table8[i - 1];
const float y2 = m_table8[i];
Q_ASSERT(v >= y1 && v <= y2);
const float fr = (v - y1) / (y2 - y1);
return (i + fr) * (1.0f / (m_tableSize - 1));
}
return x;
}
bool asColorTransferFunction(QColorTransferFunction *transferFn)
{
Q_ASSERT(transferFn);
if (m_tableSize < 2)
return false;
if (!m_table8.isEmpty() && (m_table8[0] != 0 || m_table8[m_tableSize - 1] != 255))
return false;
if (!m_table16.isEmpty() && (m_table16[0] != 0 || m_table16[m_tableSize - 1] != 65535))
return false;
if (m_tableSize == 2) {
*transferFn = QColorTransferFunction(); // Linear
return true;
}
// The following heuristics are based on those from Skia:
if (m_tableSize == 26 && !m_table16.isEmpty()) {
// code.facebook.com/posts/411525055626587/under-the-hood-improving-facebook-photos
if (m_table16[6] != 3062)
return false;
if (m_table16[12] != 12824)
return false;
if (m_table16[18] != 31237)
return false;
*transferFn = QColorTransferFunction::fromSRgb();
return true;
}
if (m_tableSize == 1024 && !m_table16.isEmpty()) {
// HP and Canon sRGB gamma tables:
if (m_table16[257] != 3366)
return false;
if (m_table16[513] != 14116)
return false;
if (m_table16[768] != 34318)
return false;
*transferFn = QColorTransferFunction::fromSRgb();
return true;
}
if (m_tableSize == 4096 && !m_table16.isEmpty()) {
// Nikon, Epson, and lcms2 sRGB gamma tables:
if (m_table16[515] != 960)
return false;
if (m_table16[1025] != 3342)
return false;
if (m_table16[2051] != 14079)
return false;
*transferFn = QColorTransferFunction::fromSRgb();
return true;
}
return false;
}
friend inline bool operator!=(const QColorTransferTable &t1, const QColorTransferTable &t2);
friend inline bool operator==(const QColorTransferTable &t1, const QColorTransferTable &t2);
uint32_t m_tableSize;
QList<uint8_t> m_table8;
QList<uint16_t> m_table16;
};
inline bool operator!=(const QColorTransferTable &t1, const QColorTransferTable &t2)
{
if (t1.m_tableSize != t2.m_tableSize)
return true;
if (t1.m_table8.isEmpty() != t2.m_table8.isEmpty())
return true;
if (t1.m_table16.isEmpty() != t2.m_table16.isEmpty())
return true;
if (!t1.m_table8.isEmpty()) {
for (uint32_t i = 0; i < t1.m_tableSize; ++i) {
if (t1.m_table8[i] != t2.m_table8[i])
return true;
}
}
if (!t1.m_table16.isEmpty()) {
for (uint32_t i = 0; i < t1.m_tableSize; ++i) {
if (t1.m_table16[i] != t2.m_table16[i])
return true;
}
}
return false;
}
inline bool operator==(const QColorTransferTable &t1, const QColorTransferTable &t2)
{
return !(t1 != t2);
}
QT_END_NAMESPACE
#endif // QCOLORTRANSFERTABLE_P_H
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