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Improve results when chroma is very low

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Desmis
2020-03-06 10:41:58 +01:00
parent f6c5bf0a0b
commit 9773f1bd98
3 changed files with 47 additions and 13 deletions
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30
rtengine/rawimagesource.cc
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@@ -4412,19 +4412,19 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
Copyright (c) Jacques Desmis 6 - 2018 jdesmis@gmail.com
Copyright (c) Ingo Weyrich 3 - 2020 (heckflosse67@gmx.de)
This algorithm try to find temperature correlation between 20 to 203 color between 200 spectral color and about 20 to 55 color found in the image, I just found the idea in the web "correlate with chroma" instead of RGB grey point,but I don't use any algo found on the web.
This algorithm try to find temperature correlation between 20 to 201 color between 200 spectral color and about 20 to 55 color found in the image, I just found the idea in the web "correlate with chroma" instead of RGB grey point,but I don't use any algo found on the web.
I have test many many algorithms to find the first one that work :)
Probably (sure) there are improvement to do...
I have create a table temperature with temp and white point with 100 values between 2000K and 12000K we can obviously change these values, more...with different steps
I have create or recuparate and transformed 203 spectral colors from Colorchecker24, others color and my 468 colors target, or from web flowers, etc. with a step of 5nm, I think it is large enough.
I think this value of 203 is now complete: I tested correlation with 60, 90, 100, 120, 155...better student increase with number of color, but now it seems stabilized
I have create or recuparate and transformed 201 spectral colors from Colorchecker24, others color and my 468 colors target, or from web flowers, etc. with a step of 5nm, I think it is large enough.
I think this value of 201 is now complete: I tested correlation with 60, 90, 100, 120, 155...better student increase with number of color, but now it seems stabilized
Of course we can increase this number :)
1) for the current raw file we create a table for each temp of RGB multipliers
2) then, I choose the "camera temp" to initialize calculation (why not)
3) for this temp, I calculated XYZ values for the 203 spectral datas
3) for this temp, I calculated XYZ values for the 201 spectral datas
4) then I create for the image an "histogram", but for xyY (Cie 1931 color space)
5) for each pixel (in fact to accelerate only 1/10 for and 1/10 for y), I determine for each couple xy, the number of occurences
6) I sort this result in ascending order
@@ -4764,7 +4764,7 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
{12001., 0.960440, 1.601019}
};
const int N_t = sizeof(Txyz) / sizeof(Txyz[0]); //number of temperature White point
constexpr int Nc = 200 + 1;//200 number of reference spectral colors, I think it is enough to retrieve good values
constexpr int Nc = 201 + 1;//200 number of reference spectral colors, I think it is enough to retrieve good values
array2D<float> Tx(N_t, Nc);
array2D<float> Ty(N_t, Nc);
array2D<float> Tz(N_t, Nc);
@@ -4863,7 +4863,7 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
array2D<float> reff_spect_xx_camera(N_t, 2 * Nc + 2);
//here we select the good spectral color inside the 113 values
//call tempxy to calculate for 203 color references Temp and XYZ with cat02
//call tempxy to calculate for 201 color references Temp and XYZ with cat02
ColorTemp::tempxy(separated, repref, Tx, Ty, Tz, Ta, Tb, TL, TX, TY, TZ, wbpar); //calculate chroma xy (xyY) for Z known colors on under 200 illuminants
@@ -4998,7 +4998,9 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
}
estimchrom /= sizcu4;
if (settings->verbose) {
printf("estimchrom=%f\n", estimchrom);
}
if (settings->itcwb_sort) { //sort in ascending with chroma values
std::sort(wbchro, wbchro + sizcu4, wbchro[0]);
}
@@ -5021,7 +5023,7 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
int maxnb = rtengine::LIM(settings->itcwb_sizereference, 1, 5);
if (settings->itcwb_thres > 39) {
maxnb = 203 / settings->itcwb_thres;
maxnb = 201 / settings->itcwb_thres;
}
for (int nb = 1; nb <= maxnb; ++nb) { //max 5 iterations for Itcwb_thres=33, after trial 3 is good in most cases but in some cases 5
@@ -5178,13 +5180,14 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
}
//degrade correllation with color high chroma, but not too much...seems not good, but keep in case of??
if (estimchrom < 0.025f) {//very smal value of chroma for image
//I suppress this old behavior replace by tint += 0.02
/* if (estimchrom < 0.025f) {//very smal value of chroma for image
//enable strong values
good_spectral[0] = true;//blue
good_spectral[11] = true;//green
good_spectral[62] = true;//red
}
*/
int kkg = -1;
for (int i = 0; i < Nc ; ++i) {
if (good_spectral[i]) {
@@ -5253,7 +5256,10 @@ void RawImageSource::ItcWB(bool extra, double &tempref, double &greenref, double
tempitc = Txyz[goodref].Tem;
greenitc = gree[greengood].green;
if (estimchrom < 0.025f) {
float ac = -2.40f * estimchrom + 0.06f;//small empirical correction, maximum 0.06 if chroma=0 for all image, currently for very low chroma +0.02
greenitc += ac;
}
}
avg_rm = 10000.f * rmm[goodref];