PSP8 Selection puzzle

[terrypin]

As shown below, I used the magic wand on a the solid black (0,0,0) border of an empty rectangle, based on RGB and with zero tolerance, expecting it to be neatly selected. Why is the region actually selected so strange please?



FWIW, if I set Match Mode to Opacity, then just the black border is selected.

--
Terry, East Grinstead, UK

[terrypin]

I think I may now understand this after some more thought. Is it simply that the same black was used for the shadow, but with a very low opacity? And the wand identifies it as black, ignoring the opacity.

I'd been regarding RGB mode as a sort of 'Appearance' mode, but that' simplification is plainly not valid.

--
Terry, East Grinstead, UK

[LeviFiction]

Pretty much.

Opacity is the only match mode that is picky about the opacity value of the pixels. All other modes only care if the opacity value is greater than 0.