Selection Tolerance

[cosmarchy]

I'm trying to select the entire length of the black line:

No matter what I set the Magic Wand tolerance to, I can only select part of the line. 

 

Is it possible to select the entirety of the black line?

 

Thanks

[MJW]

45 minutes ago, cosmarchy said:

No matter what I set the Magic Wand tolerance to, I can only select part of the line.

 

The problem is that the fill algorithm which does the Magic Wand selection does a 4-connected, not an 8-connected, fill. That means pixels are only considered to be connected if they touch at the sides, not if they touch at either the sides or the corners. Therefore, no matter what the tolerance, the the pixels at the ends of the selection you show will not be connected -- they only touch at the corners. There are good reasons why the Magic Wand uses a 4-connected fill rather than an 8-connected fill, though obviously that doesn't help you.

 

The only thing that immediately comes to mind is to duplicate the layer, apply a one-pixel blur to the duplicate, use the Magic Wand to select the blurred line, then switch to the non-blurred layer. Then use an Intersect Global Magic Wand selection (with a low tolerance) to select only the black pixels within the selection. Sorry I can't think of something simpler and more reliable.

[cosmarchy]

Well, it does it for me 😁

 

Thanks very much.

[AndrewDavid]

@cosmarchy

 

An easier method.

 

Draw a selection box that includes the entire line. 500 X 750.

 

"To remove portions from an existing selection, hold down the Alt key while creating another selection."

 

Change to Magic wand, hold down the Alt key, and Left Click on the two grey areas.

 

This will reduce the selection to the black line only. Copy and paste on a new layer.

 

Hope this helps