Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Exactly what quality of the image do you need to change, please? 'gradient' is not telling me much, I'm sorry to have to say. Shade? Brightness? color perhaps, somehow?
When I look at that image, what I am getting is an orange-yellow background, and blue foreground details.
I'm not sure I can repair that.
I regret it, and have Opted Out in favor of another Expert, with apologies.