React Canvas, detect region in image at mouse click position

I have a canvas with this image

I want when I click into canvas I will the region at position that I clicked

Example when I click into red dot, I will get region 1-2-3-4-5-6

// input: mousePosition: {x, y}
// output: listPoint: [
//  {x1, y1},
//  {x2, y2},
//  ...
//  {x6, y6}
// ]

Does anyone have any ideas or any tools that could help me. Thank you

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