gradient of the image

edit

Okay first of all some questions for you

1. Is this an image you processed with openCV code? If so please add your code to reach this result. Or did you just copied it from the net?
2. You want just a basic explanation on image gradients?

Basically image gradients are the change in intensity values of a grayscale image over the locations, the higher the change in intensity the more edge you will detect in the gradient.

However this image doesn't look like a gradient image at all ... so I am asking you where you get this from.

How to calculate the gradient can be read here.

How to create this using openCV can be read here with a correctly working example. This example uses the sobel operator for the functionality, which is one way of calculating gradients.

And to answer to the second question, that is NOT a gradient image, unless there is something very wrong...