Selection: respect alpha values for selections.

[dsizzle]

This is needed for features like blurred/feathered selection edges, and painted selections.

Fixes #363

This also allows you to do cool effects. For example, draw a stroke or two with the Airbrush, then choose "Select all non-transparent" and you get something like so:

...and then you can just do a gradient fill and it says within the exact shape of the selection because the alpha of the selection is preserved:

[humdingerb]

That's really cool! I tried to replicate your example, but for some reason it doesn't quite work. When I try to apply the gradient fill, the anty selection outline disappears (no CPU spike) and the fill tools gradient preview line stays on. Until I move the mouse pointer outside the canvas window. Then the outline re-apears and the preview-line is gone. No gradient though...

[dsizzle]

Hmm, I’ll try it some more tomorrow. I forgot one step I did in the middle, in case it makes a difference: I created a new layer and drew the gradient on the new layer.

[humdingerb]

Indeed, adding a new layer and doing the grdient fill there makes all the difference.

[dsizzle]

It actually also works for me without the extra layer, as long as my Threshold is not 0.

But, the behavior you described seems to be a bug even without this change. Filed #598 for it.

One note about this change is that it only works for "Select all non-transparent" selections... magic wand selections should also care about alpha, maybe? Or maybe it should just be blurred or painted selections when we have those, and the current behavior is correct?

[humdingerb]

It actually also works for me without the extra layer, as long as my Threshold is not 0.

Maybe depends on the exact airbrush stroke. For me it also does work in the same layer, but only perfectly when threshold is 100. Below it, I get islands of non-filled airbrush stroke.

[dsizzle]

hmm, I realize I need to change more stuff - selection data is saved as polygons, not the bitmaps - so alpha data is lost on undo/redo.

[dsizzle]

Yep. I knew this was too easy.

Filed #621 for a needed feature for this. This is the gift that keeps on giving...

[dsizzle]

ok, I think this is FINALLY done. @humdingerb if you have a chance, please test this - I believe I successfully tested all of these and they work:

1. Edit->Translate->Active layer
2. Edit->Translate->All layers
3. Selection->Translate
4. Edit->Rotate->Active layer
5. Edit->Rotate->All layers
6. Selection->Rotate
7. Edit->Scale->Active layer
8. Edit->Scale->All layers
9. Selection->Scale
10. Edit->Flip horizontally
11. Edit->Flip vertically

... as well as undoing and redoing. please let me know if you find any problems. They should all "just work" as before.

[humdingerb]

Looks good! \o/ Took you long enough... :) :) :)

[dsizzle]

Thanks! Merged!

Took you long enough... :) :) :)

You have no idea how sick of this change I am... :D