How to reverse engineer gradients back to a logical representation?

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I am trying to identify gradients in an image and then make a logical representation of the gradient which can then be converted to SVG output. There are so many types of gradients in images, linear gradients, circular gradients, simply search at google for https://www.google.com.hk/search?q=gr...

Assuming my code did already find a gradient, how can it then go about converting it to a logical representation which could then be converted to SVG?