Now this may seem a bit redundant, but hold up.
Say I had 2 square selections in a grid. (see picture 1).
But I want to select all the grid, including the lines, however the grid is blending in with the outside.
So if there were a tool that could take two or more selections and make a rectangle from them, then select that like this (see picture 2):
then that would be awesome, even if it was a plugin.
If it was a plugin, then I think it could also have a mode that takes each selection, draws lines to connect the edges, and makes a selection out of that (see picture 3 and 4).
Sorry for making an ugly mess out of everything, but I feel that this would help make selections easier instead of having to every selection pixel-perfect and manually.
So, in summary:
Selection From Selections can be a tool to average out a series of selections and select what's in between.
Rectangle mode makes a rectangle from the furthest-outward points in the selections.
Lasso mode simply draws lines between the edges of the selections, and tries its best at drawing a crude, rounded polygon. (Or we could make it simpler, and just have it take points from the furthest-outward selections and draw edges between those to make a shape.)
Thank you for reading.