How to save and import gTruth objects

This seems like a simple problem, but I am trying to save a labeled image as a gTruth object from the Image Labeler. I can export from the Image Labeler to the workspace as a gTruth, but I would like to be able to load it programatically rather than manually importing to the workspace each time. When I save the gTruth variable from my workspave and load it in later, it loads as a struct, which does not work with pixelLabelTrainingData. How do I save a gTruth and have it load back as a gTruth?

% Porcelain_gTruth exists as a gTruth in the workspace from Image Labeler
save('Porcelain_gTruth.mat','Porcelain_gTruth')

% Later on
gTruth = load('Porcelain_gTruth.mat','Porcelain_gTruth');
% Now gTruth is a struct
[imds, pxds] = pixelLabelTrainingData(gTruth);

% I will get an error along the lines of:
% Error using pixelLabelTrainingData>parseInputs
% The value of 'gTruth' is invalid. Expected input to be one of these types:
%
% groundTruth
%
% Instead its type was struct.

[Walter Roberson]

Please show us

class(Porcelain_gTruth)
whos -file Porcelain_gTruth.mat

Answer 1

[Walter Roberson]

gTruth = load('Porcelain_gTruth.mat','Porcelain_gTruth');

That form of load() does not return just the variable you asked to load. That form of load() returns a struct with one field for each variable that is loaded. You need something like

data = load('Porcelain_gTruth.mat','Porcelain_gTruth');
gTruth = data.Porcelain_gTruth;

[Max Salter]

Thank you so much!