Contents

Illuminant correction

Calculate illuminant correction matrices for a surface reflectance chart and collection of illuminants. Each matrix converts the data obtained under a test illuminant into an estimate of the sensor data under a standard illuminant (D65 in this case).

One could then transform the sensor data into a standard space such as XYZ, assuming that we know the illuminant (D65).

N.B. There are still some edits to come for the part at the end.

See also:

% Copyright ImagEval Consultants, LLC, 2016

ieInit

Create the N-100 reflectance chart

Alternatively, you can choose the scene surface reflectances here this way, if you want.

Choose some example reflectance data sFiles = cell(1,2); sFiles{1} = fullfile(isetRootPath,'data','surfaces','reflectances','MunsellSamples_Vhrel.mat'); sFiles{2} = fullfile(isetRootPath,'data','surfaces','reflectances','Food_Vhrel.mat');

% Row and column size for the reflectance chart sSamples = [48 16];

% Spatial samples for each square patch pSize = 20;

% Create the scene, storing the specific surface samples (sSamples) [scene, sSamples] = sceneReflectanceChart(sFiles,sSamples,pSize); scene = sceneSet(scene,'name','surface chart');

scene = sceneCreate('reflectance chart');
ieAddObject(scene); sceneWindow;

Create an oi and a sensor

oi = oiCreate;

% Set the sensor of interest here
nikon = sensorCreate;
wave  = sensorGet(nikon,'wave');

% Load up  Nikon color filters and an infrared
nikon = sensorSet(nikon,'infrared',ieReadSpectra('infrared2',wave));
nikon = sensorSet(nikon,'color filters',ieReadSpectra('NikonD70',wave));
nikon = sensorSetSizeToFOV(nikon,sceneGet(scene,'fov'),oi);

Display the scene over a range of blackbody illuminants

bbodyList = (3000:1500:7500);
nIlluminant = length(bbodyList);
oIP = ipCreate;

% We could put in a transform selected by imageSensorCorrection
%    oVci = ipSet(oVci,'color conversion transform',VAL);
%    oVci = ipSet(oVci,'Sensor Correction Method','mcc optimized');
%    oVci = ipSet(oVci,'Illuminant Correction Method','gray world');
%    oVci = ipSet(oVci,'Internal CS','XYZ');

oIP = ipSet(oIP,'Transform method','adaptive');
oIP = ipSet(oIP,'conversion method Sensor ','none');
oIP = ipSet(oIP,'correction method Illuminant ','none');
oIP = ipSet(oIP,'Internal CS','sensor');

% Adjust the scene illuminant SPD and compute a series of rendered images.
vci = cell(1,nIlluminant);
for ii=1:nIlluminant
    scene = sceneAdjustIlluminant(scene,blackbody(wave,bbodyList(ii),'energy'));
    scene = sceneAdjustLuminance(scene,100);
    scene = sceneSet(scene,'name',sprintf('surface %.1f',bbodyList(ii)));
    ieAddObject(scene);   % sceneWindow;

    oi = oiCompute(oi,scene);
    ieAddObject(oi);      % oiWindow;

    nikon = sensorCompute(nikon,oi);
    ieAddObject(nikon);   % sensorWindow;

    vci{ii} = ipCompute(oIP,nikon);
    vci{ii} = ipSet(vci{ii},'name',sprintf('BB %d',bbodyList(ii)));
    ieAddObject(vci{ii});
end
ipWindow;

Now put in the transform method

IN PROGRESS

Published with MATLAB® R2024a