Are these costumes different?

I have a project that Im working on that involves a lot of STAMPing. I decided to remake some of the costumes, and suddenly, everything was getting anti-aliased. so, is there a difference between these two costumes (besides the black pixels in the corners)?
the top one doesn't get anti-aliased, but the bottom one does.
I think this might have something to do with file format or something like that, but I'm not sure.
thanks for any help

Edit: apparently, if I change all of the costumes that are actually used in the project to the new ones, but leave the unused costumes unchanged, it still works, and doesn't get anti-aliased

this is so weird
(project link below)

project link: Block Game
(when I run this project, the STAMPed costumes don't blur.)

perhaps its because if it was anti-aliased the black pixels wouldnt be visible

No, I edited the top one to remove the black pixels,
But when I imported it into Snap! it got anti-aliased,
Even though the original didn’t.

then idk whats happening

yeah me neither.

does anyone know why snap! would only anti-alias certain costumes?

I just discovered that the ones that didn't get anti-aliased actually do, but only in fullscreen mode. (or if you enlarge the stage)

bump. I still want help with this

Yeah, really it should be an option. The paint editor was designed for costumes that are, you know, costumes: wizards or footballs or bananas, then anti-aliasing is the right thing. But for abstract shapes like your squares, it's a pain in the neck and should be turned off. I have this problem a lot too. Maybe someday Snap! will have a built in AI that decides for you. ;~)

a setting for the project (or if possible, for each costume,) for anti-aliasing would be nice.
or just making it so it uses non anti-aliased versions for things like STAMP and PASTE would work too

in my project though, at least for me, the sprites don't get anti-aliased. is that the same for you or is it just a thing with my system?

I think what triggers it is actually changing something in the bitmap using the costume editor. If you just want a square, you can make it with the NEW COSTUME block and avoid the editor altogether.

Ok. I made these costumes with an external editor though.
Do you think the costumes could be converted using

Yes, but if your external editor already anti-aliased the costume, we can't un-anti-alias it.

It didn’t, it’s just that the costume gets anti-aliased when used in snap!

Then I guess I don't really know how it works in detail!

update: when I used the project on a different device the costumes were anti aliased again. both devices were MacBooks with safari, but the one where the costumes were anti-aliased was newer.
can other people try the project and tell me if white lines appear between the blocks or if the world gets blurry when placing blocks with Z or by clicking the stage
Thank you