1 /*****************************************************************************/
2 // Copyright 2006 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 /* $Id: //mondo/dng_sdk_1_4/dng_sdk/source/dng_temperature.cpp#1 $ */
10 /* $DateTime: 2012/05/30 13:28:51 $ */
11 /* $Change: 832332 $ */
12 /* $Author: tknoll $ */
13
14 #include "dng_temperature.h"
15
16 #include "dng_xy_coord.h"
17
18 /*****************************************************************************/
19
20 // Scale factor between distances in uv space to a more user friendly "tint"
21 // parameter.
22
23 static const real64 kTintScale = -3000.0;
24
25 /*****************************************************************************/
26
27 // Table from Wyszecki & Stiles, "Color Science", second edition, page 228.
28
29 struct ruvt
30 {
31 real64 r;
32 real64 u;
33 real64 v;
34 real64 t;
35 };
36
37 static const ruvt kTempTable [] =
38 {
39 { 0, 0.18006, 0.26352, -0.24341 },
40 { 10, 0.18066, 0.26589, -0.25479 },
41 { 20, 0.18133, 0.26846, -0.26876 },
42 { 30, 0.18208, 0.27119, -0.28539 },
43 { 40, 0.18293, 0.27407, -0.30470 },
44 { 50, 0.18388, 0.27709, -0.32675 },
45 { 60, 0.18494, 0.28021, -0.35156 },
46 { 70, 0.18611, 0.28342, -0.37915 },
47 { 80, 0.18740, 0.28668, -0.40955 },
48 { 90, 0.18880, 0.28997, -0.44278 },
49 { 100, 0.19032, 0.29326, -0.47888 },
50 { 125, 0.19462, 0.30141, -0.58204 },
51 { 150, 0.19962, 0.30921, -0.70471 },
52 { 175, 0.20525, 0.31647, -0.84901 },
53 { 200, 0.21142, 0.32312, -1.0182 },
54 { 225, 0.21807, 0.32909, -1.2168 },
55 { 250, 0.22511, 0.33439, -1.4512 },
56 { 275, 0.23247, 0.33904, -1.7298 },
57 { 300, 0.24010, 0.34308, -2.0637 },
58 { 325, 0.24702, 0.34655, -2.4681 },
59 { 350, 0.25591, 0.34951, -2.9641 },
60 { 375, 0.26400, 0.35200, -3.5814 },
61 { 400, 0.27218, 0.35407, -4.3633 },
62 { 425, 0.28039, 0.35577, -5.3762 },
63 { 450, 0.28863, 0.35714, -6.7262 },
64 { 475, 0.29685, 0.35823, -8.5955 },
65 { 500, 0.30505, 0.35907, -11.324 },
66 { 525, 0.31320, 0.35968, -15.628 },
67 { 550, 0.32129, 0.36011, -23.325 },
68 { 575, 0.32931, 0.36038, -40.770 },
69 { 600, 0.33724, 0.36051, -116.45 }
70 };
71
72 /*****************************************************************************/
73
Set_xy_coord(const dng_xy_coord & xy)74 void dng_temperature::Set_xy_coord (const dng_xy_coord &xy)
75 {
76
77 // Convert to uv space.
78
79 real64 u = 2.0 * xy.x / (1.5 - xy.x + 6.0 * xy.y);
80 real64 v = 3.0 * xy.y / (1.5 - xy.x + 6.0 * xy.y);
81
82 // Search for line pair coordinate is between.
83
84 real64 last_dt = 0.0;
85
86 real64 last_dv = 0.0;
87 real64 last_du = 0.0;
88
89 for (uint32 index = 1; index <= 30; index++)
90 {
91
92 // Convert slope to delta-u and delta-v, with length 1.
93
94 real64 du = 1.0;
95 real64 dv = kTempTable [index] . t;
96
97 real64 len = sqrt (1.0 + dv * dv);
98
99 du /= len;
100 dv /= len;
101
102 // Find delta from black body point to test coordinate.
103
104 real64 uu = u - kTempTable [index] . u;
105 real64 vv = v - kTempTable [index] . v;
106
107 // Find distance above or below line.
108
109 real64 dt = - uu * dv + vv * du;
110
111 // If below line, we have found line pair.
112
113 if (dt <= 0.0 || index == 30)
114 {
115
116 // Find fractional weight of two lines.
117
118 if (dt > 0.0)
119 dt = 0.0;
120
121 dt = -dt;
122
123 real64 f;
124
125 if (index == 1)
126 {
127 f = 0.0;
128 }
129 else
130 {
131 f = dt / (last_dt + dt);
132 }
133
134 // Interpolate the temperature.
135
136 fTemperature = 1.0E6 / (kTempTable [index - 1] . r * f +
137 kTempTable [index ] . r * (1.0 - f));
138
139 // Find delta from black body point to test coordinate.
140
141 uu = u - (kTempTable [index - 1] . u * f +
142 kTempTable [index ] . u * (1.0 - f));
143
144 vv = v - (kTempTable [index - 1] . v * f +
145 kTempTable [index ] . v * (1.0 - f));
146
147 // Interpolate vectors along slope.
148
149 du = du * (1.0 - f) + last_du * f;
150 dv = dv * (1.0 - f) + last_dv * f;
151
152 len = sqrt (du * du + dv * dv);
153
154 du /= len;
155 dv /= len;
156
157 // Find distance along slope.
158
159 fTint = (uu * du + vv * dv) * kTintScale;
160
161 break;
162
163 }
164
165 // Try next line pair.
166
167 last_dt = dt;
168
169 last_du = du;
170 last_dv = dv;
171
172 }
173
174 }
175
176 /*****************************************************************************/
177
Get_xy_coord() const178 dng_xy_coord dng_temperature::Get_xy_coord () const
179 {
180
181 dng_xy_coord result;
182
183 // Find inverse temperature to use as index.
184
185 real64 r = 1.0E6 / fTemperature;
186
187 // Convert tint to offset is uv space.
188
189 real64 offset = fTint * (1.0 / kTintScale);
190
191 // Search for line pair containing coordinate.
192
193 for (uint32 index = 0; index <= 29; index++)
194 {
195
196 if (r < kTempTable [index + 1] . r || index == 29)
197 {
198
199 // Find relative weight of first line.
200
201 real64 f = (kTempTable [index + 1] . r - r) /
202 (kTempTable [index + 1] . r - kTempTable [index] . r);
203
204 // Interpolate the black body coordinates.
205
206 real64 u = kTempTable [index ] . u * f +
207 kTempTable [index + 1] . u * (1.0 - f);
208
209 real64 v = kTempTable [index ] . v * f +
210 kTempTable [index + 1] . v * (1.0 - f);
211
212 // Find vectors along slope for each line.
213
214 real64 uu1 = 1.0;
215 real64 vv1 = kTempTable [index] . t;
216
217 real64 uu2 = 1.0;
218 real64 vv2 = kTempTable [index + 1] . t;
219
220 real64 len1 = sqrt (1.0 + vv1 * vv1);
221 real64 len2 = sqrt (1.0 + vv2 * vv2);
222
223 uu1 /= len1;
224 vv1 /= len1;
225
226 uu2 /= len2;
227 vv2 /= len2;
228
229 // Find vector from black body point.
230
231 real64 uu3 = uu1 * f + uu2 * (1.0 - f);
232 real64 vv3 = vv1 * f + vv2 * (1.0 - f);
233
234 real64 len3 = sqrt (uu3 * uu3 + vv3 * vv3);
235
236 uu3 /= len3;
237 vv3 /= len3;
238
239 // Adjust coordinate along this vector.
240
241 u += uu3 * offset;
242 v += vv3 * offset;
243
244 // Convert to xy coordinates.
245
246 result.x = 1.5 * u / (u - 4.0 * v + 2.0);
247 result.y = v / (u - 4.0 * v + 2.0);
248
249 break;
250
251 }
252
253 }
254
255 return result;
256
257 }
258
259 /*****************************************************************************/
260