1 /*****************************************************************************/
2 // Copyright 2006-2019 Adobe Systems Incorporated
3 // All Rights Reserved.
4 //
5 // NOTICE: Adobe permits you to use, modify, and distribute this file in
6 // accordance with the terms of the Adobe license agreement accompanying it.
7 /*****************************************************************************/
8
9 #include "dng_temperature.h"
10
11 #include "dng_xy_coord.h"
12
13 /*****************************************************************************/
14
15 // Scale factor between distances in uv space to a more user friendly "tint"
16 // parameter.
17
18 static const real64 kTintScale = -3000.0;
19
20 /*****************************************************************************/
21
22 // Table from Wyszecki & Stiles, "Color Science", second edition, page 228.
23
24 struct ruvt
25 {
26 real64 r;
27 real64 u;
28 real64 v;
29 real64 t;
30 };
31
32 static const ruvt kTempTable [] =
33 {
34 { 0, 0.18006, 0.26352, -0.24341 },
35 { 10, 0.18066, 0.26589, -0.25479 },
36 { 20, 0.18133, 0.26846, -0.26876 },
37 { 30, 0.18208, 0.27119, -0.28539 },
38 { 40, 0.18293, 0.27407, -0.30470 },
39 { 50, 0.18388, 0.27709, -0.32675 },
40 { 60, 0.18494, 0.28021, -0.35156 },
41 { 70, 0.18611, 0.28342, -0.37915 },
42 { 80, 0.18740, 0.28668, -0.40955 },
43 { 90, 0.18880, 0.28997, -0.44278 },
44 { 100, 0.19032, 0.29326, -0.47888 },
45 { 125, 0.19462, 0.30141, -0.58204 },
46 { 150, 0.19962, 0.30921, -0.70471 },
47 { 175, 0.20525, 0.31647, -0.84901 },
48 { 200, 0.21142, 0.32312, -1.0182 },
49 { 225, 0.21807, 0.32909, -1.2168 },
50 { 250, 0.22511, 0.33439, -1.4512 },
51 { 275, 0.23247, 0.33904, -1.7298 },
52 { 300, 0.24010, 0.34308, -2.0637 },
53 { 325, 0.24702, 0.34655, -2.4681 },
54 { 350, 0.25591, 0.34951, -2.9641 },
55 { 375, 0.26400, 0.35200, -3.5814 },
56 { 400, 0.27218, 0.35407, -4.3633 },
57 { 425, 0.28039, 0.35577, -5.3762 },
58 { 450, 0.28863, 0.35714, -6.7262 },
59 { 475, 0.29685, 0.35823, -8.5955 },
60 { 500, 0.30505, 0.35907, -11.324 },
61 { 525, 0.31320, 0.35968, -15.628 },
62 { 550, 0.32129, 0.36011, -23.325 },
63 { 575, 0.32931, 0.36038, -40.770 },
64 { 600, 0.33724, 0.36051, -116.45 }
65 };
66
67 /*****************************************************************************/
68
Set_xy_coord(const dng_xy_coord & xy)69 void dng_temperature::Set_xy_coord (const dng_xy_coord &xy)
70 {
71
72 // Convert to uv space.
73
74 real64 u = 2.0 * xy.x / (1.5 - xy.x + 6.0 * xy.y);
75 real64 v = 3.0 * xy.y / (1.5 - xy.x + 6.0 * xy.y);
76
77 // Search for line pair coordinate is between.
78
79 real64 last_dt = 0.0;
80
81 real64 last_dv = 0.0;
82 real64 last_du = 0.0;
83
84 for (uint32 index = 1; index <= 30; index++)
85 {
86
87 // Convert slope to delta-u and delta-v, with length 1.
88
89 real64 du = 1.0;
90 real64 dv = kTempTable [index] . t;
91
92 real64 len = sqrt (1.0 + dv * dv);
93
94 du /= len;
95 dv /= len;
96
97 // Find delta from black body point to test coordinate.
98
99 real64 uu = u - kTempTable [index] . u;
100 real64 vv = v - kTempTable [index] . v;
101
102 // Find distance above or below line.
103
104 real64 dt = - uu * dv + vv * du;
105
106 // If below line, we have found line pair.
107
108 if (dt <= 0.0 || index == 30)
109 {
110
111 // Find fractional weight of two lines.
112
113 if (dt > 0.0)
114 dt = 0.0;
115
116 dt = -dt;
117
118 real64 f;
119
120 if (index == 1)
121 {
122 f = 0.0;
123 }
124 else
125 {
126 f = dt / (last_dt + dt);
127 }
128
129 // Interpolate the temperature.
130
131 fTemperature = 1.0E6 / (kTempTable [index - 1] . r * f +
132 kTempTable [index ] . r * (1.0 - f));
133
134 // Find delta from black body point to test coordinate.
135
136 uu = u - (kTempTable [index - 1] . u * f +
137 kTempTable [index ] . u * (1.0 - f));
138
139 vv = v - (kTempTable [index - 1] . v * f +
140 kTempTable [index ] . v * (1.0 - f));
141
142 // Interpolate vectors along slope.
143
144 du = du * (1.0 - f) + last_du * f;
145 dv = dv * (1.0 - f) + last_dv * f;
146
147 len = sqrt (du * du + dv * dv);
148
149 du /= len;
150 dv /= len;
151
152 // Find distance along slope.
153
154 fTint = (uu * du + vv * dv) * kTintScale;
155
156 break;
157
158 }
159
160 // Try next line pair.
161
162 last_dt = dt;
163
164 last_du = du;
165 last_dv = dv;
166
167 }
168
169 }
170
171 /*****************************************************************************/
172
Get_xy_coord() const173 dng_xy_coord dng_temperature::Get_xy_coord () const
174 {
175
176 dng_xy_coord result;
177
178 // Find inverse temperature to use as index.
179
180 real64 r = 1.0E6 / fTemperature;
181
182 // Convert tint to offset is uv space.
183
184 real64 offset = fTint * (1.0 / kTintScale);
185
186 // Search for line pair containing coordinate.
187
188 for (uint32 index = 0; index <= 29; index++)
189 {
190
191 if (r < kTempTable [index + 1] . r || index == 29)
192 {
193
194 // Find relative weight of first line.
195
196 real64 f = (kTempTable [index + 1] . r - r) /
197 (kTempTable [index + 1] . r - kTempTable [index] . r);
198
199 // Interpolate the black body coordinates.
200
201 real64 u = kTempTable [index ] . u * f +
202 kTempTable [index + 1] . u * (1.0 - f);
203
204 real64 v = kTempTable [index ] . v * f +
205 kTempTable [index + 1] . v * (1.0 - f);
206
207 // Find vectors along slope for each line.
208
209 real64 uu1 = 1.0;
210 real64 vv1 = kTempTable [index] . t;
211
212 real64 uu2 = 1.0;
213 real64 vv2 = kTempTable [index + 1] . t;
214
215 real64 len1 = sqrt (1.0 + vv1 * vv1);
216 real64 len2 = sqrt (1.0 + vv2 * vv2);
217
218 uu1 /= len1;
219 vv1 /= len1;
220
221 uu2 /= len2;
222 vv2 /= len2;
223
224 // Find vector from black body point.
225
226 real64 uu3 = uu1 * f + uu2 * (1.0 - f);
227 real64 vv3 = vv1 * f + vv2 * (1.0 - f);
228
229 real64 len3 = sqrt (uu3 * uu3 + vv3 * vv3);
230
231 uu3 /= len3;
232 vv3 /= len3;
233
234 // Adjust coordinate along this vector.
235
236 u += uu3 * offset;
237 v += vv3 * offset;
238
239 // Convert to xy coordinates.
240
241 result.x = 1.5 * u / (u - 4.0 * v + 2.0);
242 result.y = v / (u - 4.0 * v + 2.0);
243
244 break;
245
246 }
247
248 }
249
250 return result;
251
252 }
253
254 /*****************************************************************************/
255