Error in createsamples (cvSetImageROI)

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Hi , I m trying to create a vec file from a collection of images but I always got this error :(

my data fowlder is organised like this

         ../Traincascade/Positives/
                                   positives_001.jpg
                                   ...
                                   positives_172.jpg

and my description file is

I must precise that I resised all images at a 30*30 px (it makes the dec file easier to create) , maybe it causes this error? I really can't see where I m doing wrong :( so let me know if you find out :)

Looking forward to your answers, Regards, Luc