Opencv JS - extracting skin tones

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So for a project of mine I need to extract skin tones from an image. To do this, what I've done is converted RGB2HSV and then try to detect using a skin range found in other projects I've found that have done something similar however in opencv JS I'm forced to use the alpha channel as In order to conduct an inrange I require 4 channels instead of 3. This has significantly confused me and how I'm supposed to detect skin tones. Additionally,

here is a user with a similar problem to me but with no solution to his issue: https://stackoverflow.com/questions/4...