get images from opencv_createsamples, annotations, png files

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I followed the documentation from here and created samples using opencv_createsamples for positive images . I am trying to get these images, than storing it in .vec files.

From the documentation, there's a way to get it, as PNG or JPG files, but am not able to undertsand few things :-

    1. It asks for the back ground or negative images information. Is it going to use that to rotate and create samples of the positive images?  How exactly is the information of negative images going to help here? For example, lets say I want to detect images of cars. Can the background images be that of a ship? or should it be literally the images that come in its background.?

   2. for creating **.vec** files and samples, the background images information was not necessarily required. Does it mean that, even here, for png or jpg, it wont be used to manipulate the positive samples?

  3. I have included the back ground images as objects, that can appear in the scene , but not around the car or as its background. Am I going write or by back ground it just means th foreground-background of an image, in image processing terms?

 4. should annotations.lst be created by me or will it be done by the executable?

Please help me. I am really confused here