In the function definition
<pre><code class="cpp">
float cv::rectify3Collinear( InputArray _cameraMatrix1, InputArray _distCoeffs1,
InputArray _cameraMatrix2, InputArray _distCoeffs2,
InputArray _cameraMatrix3, InputArray _distCoeffs3,
InputArrayOfArrays _imgpt1,
InputArrayOfArrays _imgpt3,
Size imageSize, InputArray _Rmat12, InputArray _Tmat12,
InputArray _Rmat13, InputArray _Tmat13,
OutputArray _Rmat1, OutputArray _Rmat2, OutputArray _Rmat3,
OutputArray _Pmat1, OutputArray _Pmat2, OutputArray _Pmat3,
OutputArray _Qmat,
double alpha, Size /*newImgSize*/,
Rect* roi1, Rect* roi2, int flags )
</code></pre>

the argument after alpha is not given a name. Probably the comment should be removed and the variable @newImgSize@ newImgSize used accordingly instead of @imageSize@ imageSize in the calls:

<pre><code class="cpp">


stereoRectify( _cameraMatrix1, _distCoeffs1, _cameraMatrix2, _distCoeffs2,
imageSize, _Rmat12, _Tmat12, _Rmat1, _Rmat2, _Pmat1, _Pmat2, _Qmat,
flags, alpha, imageSize, roi1, roi2 );

stereoRectify( _cameraMatrix1, _distCoeffs1, _cameraMatrix2, _distCoeffs2,
imageSize, _Rmat12, _Tmat12, _Rmat1, _Rmat2, _Pmat1, _Pmat2, _Qmat,
flags, alpha, newImgSize, roi1, roi2 );
</code></pre>