Extracting region of interest (ROI) scene data

We illustrate ROIs and plotting for photons, energy, illuminant and reflectance.

Most of these cases are managed by scenePlot, though it is useful to know how to extract the data directly for computing.

Create a scene
Photons
Energy
Reflectance as XW matrix, but derived here
As above, but by the get directly
Region of interest for mean reflectance
Compute the mean reflectance here and compare
Mean illuminant in an ROI

ieInit

Create a scene

scene = sceneCreate;
w = sceneGet(scene,'wave');

Photons

sz = sceneGet(scene,'size');
roi = round( [sz(1)/2, sz(2), 10, 10]);
p = sceneGet(scene,'roi photons',roi);
meanP = sceneGet(scene, 'roi mean photons', roi);

vcNewGraphWin;
plot(w,p); hold on;
plot(w, meanP, 'r-', 'LineWidth', 2.0);
xlabel('Wavelength (nm)'); ylabel('Photons/s/sr/nm/m^2'); grid on

Energy

e = sceneGet(scene,'roi energy',roi);
meanE = sceneGet(scene, 'roi mean energy', roi);

vcNewGraphWin;
plot(w,e); hold on;
plot(w, meanE, 'r-', 'LineWidth', 2.0)
xlabel('Wavelength (nm)'); ylabel('Watts/s/sr/nm/m^2'); grid on

Reflectance as XW matrix, but derived here

photons       = sceneGet(scene,'roi photons', roi);
illuminantSPD = sceneGet(scene,'roi illuminant photons',roi);
meanIlluminantSPD = sceneGet(scene,'roi mean illuminant photons',roi);
reflectance   = photons ./ illuminantSPD;

vcNewGraphWin;
plot(w,reflectance);
xlabel('Wavelength (nm)'); ylabel('Reflectance'); grid on

As above, but by the get directly

r = sceneGet(scene,'roi reflectance', roi);

% Now compare
vcNewGraphWin;
plot(r(:),reflectance(:),'o');
title('Should be identity line'); axis equal; grid on; identityLine;

Region of interest for mean reflectance

r = sceneGet(scene,'roi mean reflectance',roi);

vcNewGraphWin;
plot(w,r);
xlabel('Wavelength (nm)'); ylabel('Watts/s/sr/nm/m^2'); grid on

Compute the mean reflectance here and compare

r2 = mean(r,1);
vcNewGraphWin;
plot(w,r,'k-',w,r2,'r--');
xlabel('Wavelength (nm)'); ylabel('Reflectance'); grid on

Mean illuminant in an ROI

illuminantSPD = sceneGet(scene,'roi illuminant photons',roi);
meanIlluminantSPD = sceneGet(scene,'roi mean illuminant photons',roi);

vcNewGraphWin;
plot(w,illuminantSPD);
xlabel('Wavelength (nm)'); ylabel('Photons/s/sr/nm/m^2'); grid on