Having the ability to make a ref/background image transparent by color

When someone use image references, he does not always have an image with alpha in it. So, there is only one solution if he wants to have his image transparent : open an image editor and create an alpha passe by color, and export as png/jpeg to blender. Not that much efficient.

We should have in blender a section in the empty rendering as image. This section contain a color selector and a threshold slider to choose the color we want to make transparent.

note : I'll add image exemples soon