Save Camera Calibration Parameters

The export of camera parameters from the Camera Calibration toolbox creates its own type of variable that cannot be saved as a .mat. How can I save these so that I can load it when I want to use that camera instead of calibrating it every time? Is xml the only way?

Thanks, Erin

[Salaheddin Hosseinzadeh]

Erin can you tell me what's the type of the variables? Struct? Cell? Char? Double? or ... ?

[Erin]

It's a 1x1 vision.CameraParameters object

[Clive Fox]

There is a command toStruct(cameraParams) which seems to work,so if you have created a cameraParameters object in your workspace

mycamParams = toStruct(cameraParams)

save mycamParams.mat mycamParams %Saves as a mat file

clear %clear variables in workspace

load('mycamParams.mat') %loads it back in and Matlab recognises it is a structure

mycamParams=cameraParameters(parameterStruct) % recreates the camera parameters object which you can then use to undistort images etc.

[Aditi Singh]

I have an image how can I find camera calibration for that.

Answer 1

[Dima Lisin]

You certainly can save the camera parameters object into a mat file, just like any other variable. Export the variable to workspace. Let's call it myParams. Then do

>> save myParams.mat myParams

That should work.

[Helia Sh]

I kept getting an error: ""Argument must contain a character vector". I slightly modified Dima's suggestion to make it work for me:

>> save 'myParams' myParams

[Matt J]

Hard to see why the modification was necessary or made any difference. Maybe you were originally using the functional form of save as follows,

save('myParams',myParams)

Answer 2

[Sean de Wolski]

With MATLAB R2014a, you can generate equivalent code with the app.

http://www.mathworks.com/help/releases/R2014a/vision/release-notes.html

[Sean de Wolski]

See the "Generate MATLAB Script" option.

[Erin]

I unfortunately have 2013b not 2014a.

[Image Analyst]

You can probably get a free upgrade if you purchased R2013b.

[Erin]

It's a company license so I can't.

Basically I am trying to save the object of the type vision.CameraParameters class. I would like to be able to save it out of my workspace so that I can just reload it to use it for undistortImage instead of rerunning the calibration each time my workspace gets cleared.

Answer 3

[Matt J]

You could write a customized save routine that exports the CameraParameters properties and saves them in a structure

function save_cameraParams(cpObject,fileName)

    fields={'IntrinsicMatrix', 'RadialDistortion',etc...}

    for ii=1:length(fields)
      S.(fields{ii})=cpObject.(fields{ii});
    end

    save(fileName, 'S');

end

Then a similar one to reload and rebuild the vision.CameraParameters object,

   function cpObject=load_cameraParams(fileName)

     S=load(fileName); S=S.S

     pairs=[fieldnames(S), struct2cell(S)].';

     cpObject=vision.CameraParameters(pairs{:});

   end