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39
40#ifndef QCOLORTRANSFERTABLE_P_H
41#define QCOLORTRANSFERTABLE_P_H
42
43//
44// W A R N I N G
45// -------------
46//
47// This file is not part of the Qt API. It exists purely as an
48// implementation detail. This header file may change from version to
49// version without notice, or even be removed.
50//
51// We mean it.
52//
53
54#include <QtGui/private/qtguiglobal_p.h>
55#include "qcolortransferfunction_p.h"
56
57#include <QList>
58#include <cmath>
59
60QT_BEGIN_NAMESPACE
61
62// Defines either an ICC TRC 'curve' or a lut8/lut16 A or B table
63class Q_GUI_EXPORT QColorTransferTable
64{
65public:
66 QColorTransferTable() noexcept
67 : m_tableSize(0)
68 { }
69 QColorTransferTable(uint32_t size, const QList<uint8_t> &table) noexcept
70 : m_tableSize(size), m_table8(table)
71 {
72 Q_ASSERT(qsizetype(size) <= table.count());
73 }
74 QColorTransferTable(uint32_t size, const QList<uint16_t> &table) noexcept
75 : m_tableSize(size), m_table16(table)
76 {
77 Q_ASSERT(qsizetype(size) <= table.count());
78 }
79
80 bool isEmpty() const
81 {
82 return m_tableSize == 0;
83 }
84
85 bool checkValidity() const
86 {
87 if (isEmpty())
88 return true;
89 // Only one table can be set
90 if (!m_table8.isEmpty() && !m_table16.isEmpty())
91 return false;
92 // At least 2 elements
93 if (m_tableSize < 2)
94 return false;
95 // The table must describe an injective curve:
96 if (!m_table8.isEmpty()) {
97 uint8_t val = 0;
98 for (uint i = 0; i < m_tableSize; ++i) {
99 if (m_table8[i] < val)
100 return false;
101 val = m_table8[i];
102 }
103 }
104 if (!m_table16.isEmpty()) {
105 uint16_t val = 0;
106 for (uint i = 0; i < m_tableSize; ++i) {
107 if (m_table16[i] < val)
108 return false;
109 val = m_table16[i];
110 }
111 }
112 return true;
113 }
114
115 float apply(float x) const
116 {
117 x = std::min(std::max(x, 0.0f), 1.0f);
118 x *= m_tableSize - 1;
119 uint32_t lo = static_cast<uint32_t>(std::floor(x));
120 uint32_t hi = std::min(lo + 1, m_tableSize - 1);
121 float frac = x - lo;
122 if (!m_table16.isEmpty())
123 return (m_table16[lo] * (1.0f - frac) + m_table16[hi] * frac) * (1.0f/65535.0f);
124 if (!m_table8.isEmpty())
125 return (m_table8[lo] * (1.0f - frac) + m_table8[hi] * frac) * (1.0f/255.0f);
126 return x;
127 }
128
129 // Apply inverse, optimized by giving a previous result a value < x.
130 float applyInverse(float x, float resultLargerThan = 0.0f) const
131 {
132 Q_ASSERT(resultLargerThan >= 0.0f && resultLargerThan <= 1.0f);
133 if (x <= 0.0f)
134 return 0.0f;
135 if (x >= 1.0f)
136 return 1.0f;
137 if (!m_table16.isEmpty()) {
138 float v = x * 65535.0f;
139 uint32_t i = std::floor(resultLargerThan * (m_tableSize - 1)) + 1;
140 for ( ; i < m_tableSize; ++i) {
141 if (m_table16[i] > v)
142 break;
143 }
144 if (i >= m_tableSize - 1)
145 return 1.0f;
146 float y1 = m_table16[i - 1];
147 float y2 = m_table16[i];
148 Q_ASSERT(x >= y1 && x < y2);
149 float fr = (v - y1) / (y2 - y1);
150 return (i + fr) * (1.0f / (m_tableSize - 1));
151
152 }
153 if (!m_table8.isEmpty()) {
154 float v = x * 255.0f;
155 uint32_t i = std::floor(resultLargerThan * (m_tableSize - 1)) + 1;
156 for ( ; i < m_tableSize; ++i) {
157 if (m_table8[i] > v)
158 break;
159 }
160 if (i >= m_tableSize - 1)
161 return 1.0f;
162 float y1 = m_table8[i - 1];
163 float y2 = m_table8[i];
164 Q_ASSERT(x >= y1 && x < y2);
165 float fr = (v - y1) / (y2 - y1);
166 return (i + fr) * (1.0f / (m_tableSize - 1));
167 }
168 return x;
169 }
170
171 bool asColorTransferFunction(QColorTransferFunction *transferFn)
172 {
173 Q_ASSERT(transferFn);
174 if (m_tableSize < 2)
175 return false;
176 if (!m_table8.isEmpty() && (m_table8[0] != 0 || m_table8[m_tableSize - 1] != 255))
177 return false;
178 if (!m_table16.isEmpty() && (m_table16[0] != 0 || m_table16[m_tableSize - 1] != 65535))
179 return false;
180 if (m_tableSize == 2) {
181 *transferFn = QColorTransferFunction(); // Linear
182 return true;
183 }
184 // The following heuristics are based on those from Skia:
185 if (m_tableSize == 26 && !m_table16.isEmpty()) {
186 // code.facebook.com/posts/411525055626587/under-the-hood-improving-facebook-photos
187 if (m_table16[6] != 3062)
188 return false;
189 if (m_table16[12] != 12824)
190 return false;
191 if (m_table16[18] != 31237)
192 return false;
193 *transferFn = QColorTransferFunction::fromSRgb();
194 return true;
195 }
196 if (m_tableSize == 1024 && !m_table16.isEmpty()) {
197 // HP and Canon sRGB gamma tables:
198 if (m_table16[257] != 3366)
199 return false;
200 if (m_table16[513] != 14116)
201 return false;
202 if (m_table16[768] != 34318)
203 return false;
204 *transferFn = QColorTransferFunction::fromSRgb();
205 return true;
206 }
207 if (m_tableSize == 4096 && !m_table16.isEmpty()) {
208 // Nikon, Epson, and lcms2 sRGB gamma tables:
209 if (m_table16[515] != 960)
210 return false;
211 if (m_table16[1025] != 3342)
212 return false;
213 if (m_table16[2051] != 14079)
214 return false;
215 *transferFn = QColorTransferFunction::fromSRgb();
216 return true;
217 }
218 return false;
219 }
220 friend inline bool operator!=(const QColorTransferTable &t1, const QColorTransferTable &t2);
221 friend inline bool operator==(const QColorTransferTable &t1, const QColorTransferTable &t2);
222
223 uint32_t m_tableSize;
224 QList<uint8_t> m_table8;
225 QList<uint16_t> m_table16;
226};
227
228inline bool operator!=(const QColorTransferTable &t1, const QColorTransferTable &t2)
229{
230 if (t1.m_tableSize != t2.m_tableSize)
231 return true;
232 if (t1.m_table8.isEmpty() != t2.m_table8.isEmpty())
233 return true;
234 if (t1.m_table16.isEmpty() != t2.m_table16.isEmpty())
235 return true;
236 if (!t1.m_table8.isEmpty()) {
237 for (uint32_t i = 0; i < t1.m_tableSize; ++i) {
238 if (t1.m_table8[i] != t2.m_table8[i])
239 return true;
240 }
241 }
242 if (!t1.m_table16.isEmpty()) {
243 for (uint32_t i = 0; i < t1.m_tableSize; ++i) {
244 if (t1.m_table16[i] != t2.m_table16[i])
245 return true;
246 }
247 }
248 return false;
249}
250
251inline bool operator==(const QColorTransferTable &t1, const QColorTransferTable &t2)
252{
253 return !(t1 != t2);
254}
255
256QT_END_NAMESPACE
257
258#endif // QCOLORTRANSFERTABLE_P_H
259