remove gradient of a image without a comparison image

Question

currently i am having much difficulty thinking of a good method of removing the gradient from a image i received.

The image is a picture taken by a microscope camera th

Answer 1

I have done some work in this area previously and found that a large Gaussian blur kernel can produce a reasonable approximation to the background illumination. I will try to get something working on your example image but, in the meantime, here is an example of your image after Gaussian blur with radius 50 pixels, which may help you decide if it's worth progressing.

UPDATE

Just playing with this image, you can actually get a reasonable improvement using adaptive histogram equalisation (I used CLAHE) - see comparison below - any use?

I will update this answer with more details as I progress.