File indexing completed on 2025-01-19 03:55:18

 /*****************************************************************************/
 // Copyright 2006-2019 Adobe Systems Incorporated
 // All Rights Reserved.
 //
 // NOTICE:  Adobe permits you to use, modify, and distribute this file in
 // accordance with the terms of the Adobe license agreement accompanying it.
 /*****************************************************************************/
 
 #include "dng_temperature.h"
 
 #include "dng_xy_coord.h"
 
 /*****************************************************************************/
 
 // Scale factor between distances in uv space to a more user friendly "tint"
 // parameter.
 
 static const real64 kTintScale = -3000.0;
 
 /*****************************************************************************/
 
 // Table from Wyszecki & Stiles, "Color Science", second edition, page 228.
 
 struct ruvt
     {
     real64 r;
     real64 u;
     real64 v;
     real64 t;
     };
 
 static const ruvt kTempTable [] =
     {
     {   0, 0.18006, 0.26352, -0.24341 },
     {  10, 0.18066, 0.26589, -0.25479 },
     {  20, 0.18133, 0.26846, -0.26876 },
     {  30, 0.18208, 0.27119, -0.28539 },
     {  40, 0.18293, 0.27407, -0.30470 },
     {  50, 0.18388, 0.27709, -0.32675 },
     {  60, 0.18494, 0.28021, -0.35156 },
     {  70, 0.18611, 0.28342, -0.37915 },
     {  80, 0.18740, 0.28668, -0.40955 },
     {  90, 0.18880, 0.28997, -0.44278 },
     { 100, 0.19032, 0.29326, -0.47888 },
     { 125, 0.19462, 0.30141, -0.58204 },
     { 150, 0.19962, 0.30921, -0.70471 },
     { 175, 0.20525, 0.31647, -0.84901 },
     { 200, 0.21142, 0.32312, -1.0182 },
     { 225, 0.21807, 0.32909, -1.2168 },
     { 250, 0.22511, 0.33439, -1.4512 },
     { 275, 0.23247, 0.33904, -1.7298 },
     { 300, 0.24010, 0.34308, -2.0637 },
     { 325, 0.24702, 0.34655, -2.4681 },
     { 350, 0.25591, 0.34951, -2.9641 },
     { 375, 0.26400, 0.35200, -3.5814 },
     { 400, 0.27218, 0.35407, -4.3633 },
     { 425, 0.28039, 0.35577, -5.3762 },
     { 450, 0.28863, 0.35714, -6.7262 },
     { 475, 0.29685, 0.35823, -8.5955 },
     { 500, 0.30505, 0.35907, -11.324 },
     { 525, 0.31320, 0.35968, -15.628 },
     { 550, 0.32129, 0.36011, -23.325 },
     { 575, 0.32931, 0.36038, -40.770 },
     { 600, 0.33724, 0.36051, -116.45 }
     };
 
 /*****************************************************************************/
 
 void dng_temperature::Set_xy_coord (const dng_xy_coord &xy)
     {
 
     // Convert to uv space.
 
     real64 u = 2.0 * xy.x / (1.5 - xy.x + 6.0 * xy.y);
     real64 v = 3.0 * xy.y / (1.5 - xy.x + 6.0 * xy.y);
 
     // Search for line pair coordinate is between.
 
     real64 last_dt = 0.0;
 
     real64 last_dv = 0.0;
     real64 last_du = 0.0;
 
     for (uint32 index = 1; index <= 30; index++)
         {
 
         // Convert slope to delta-u and delta-v, with length 1.
 
         real64 du = 1.0;
         real64 dv = kTempTable [index] . t;
 
         real64 len = sqrt (1.0 + dv * dv);
 
         du /= len;
         dv /= len;
 
         // Find delta from black body point to test coordinate.
 
         real64 uu = u - kTempTable [index] . u;
         real64 vv = v - kTempTable [index] . v;
 
         // Find distance above or below line.
 
         real64 dt = - uu * dv + vv * du;
 
         // If below line, we have found line pair.
 
         if (dt <= 0.0 || index == 30)
             {
 
             // Find fractional weight of two lines.
 
             if (dt > 0.0)
                 dt = 0.0;
 
             dt = -dt;
 
             real64 f;
 
             if (index == 1)
                 {
                 f = 0.0;
                 }
             else
                 {
                 f = dt / (last_dt + dt);
                 }
 
             // Interpolate the temperature.
 
             fTemperature = 1.0E6 / (kTempTable [index - 1] . r * f +
                                     kTempTable [index    ] . r * (1.0 - f));
 
             // Find delta from black body point to test coordinate.
 
             uu = u - (kTempTable [index - 1] . u * f +
                       kTempTable [index    ] . u * (1.0 - f));
 
             vv = v - (kTempTable [index - 1] . v * f +
                       kTempTable [index    ] . v * (1.0 - f));
 
             // Interpolate vectors along slope.
 
             du = du * (1.0 - f) + last_du * f;
             dv = dv * (1.0 - f) + last_dv * f;
 
             len = sqrt (du * du + dv * dv);
 
             du /= len;
             dv /= len;
 
             // Find distance along slope.
 
             fTint = (uu * du + vv * dv) * kTintScale;
 
             break;
 
             }
 
         // Try next line pair.
 
         last_dt = dt;
 
         last_du = du;
         last_dv = dv;
 
         }
 
     }
 
 /*****************************************************************************/
 
 dng_xy_coord dng_temperature::Get_xy_coord () const
     {
 
     dng_xy_coord result;
 
     // Find inverse temperature to use as index.
 
     real64 r = 1.0E6 / fTemperature;
 
     // Convert tint to offset is uv space.
 
     real64 offset = fTint * (1.0 / kTintScale);
 
     // Search for line pair containing coordinate.
 
     for (uint32 index = 0; index <= 29; index++)
         {
 
         if (r < kTempTable [index + 1] . r || index == 29)
             {
 
             // Find relative weight of first line.
 
             real64 f = (kTempTable [index + 1] . r - r) /
                        (kTempTable [index + 1] . r - kTempTable [index] . r);
 
             // Interpolate the black body coordinates.
 
             real64 u = kTempTable [index    ] . u * f +
                        kTempTable [index + 1] . u * (1.0 - f);
 
             real64 v = kTempTable [index    ] . v * f +
                        kTempTable [index + 1] . v * (1.0 - f);
 
             // Find vectors along slope for each line.
 
             real64 uu1 = 1.0;
             real64 vv1 = kTempTable [index] . t;
 
             real64 uu2 = 1.0;
             real64 vv2 = kTempTable [index + 1] . t;
 
             real64 len1 = sqrt (1.0 + vv1 * vv1);
             real64 len2 = sqrt (1.0 + vv2 * vv2);
 
             uu1 /= len1;
             vv1 /= len1;
 
             uu2 /= len2;
             vv2 /= len2;
 
             // Find vector from black body point.
 
             real64 uu3 = uu1 * f + uu2 * (1.0 - f);
             real64 vv3 = vv1 * f + vv2 * (1.0 - f);
 
             real64 len3 = sqrt (uu3 * uu3 + vv3 * vv3);
 
             uu3 /= len3;
             vv3 /= len3;
 
             // Adjust coordinate along this vector.
 
             u += uu3 * offset;
             v += vv3 * offset;
 
             // Convert to xy coordinates.
 
             result.x = 1.5 * u / (u - 4.0 * v + 2.0);
             result.y =       v / (u - 4.0 * v + 2.0);
 
             break;
 
             }
 
         }
 
     return result;
 
     }
 
 /*****************************************************************************/