Convex hull of bitmap costumes ignores the rightmost column and the bottom row of texels

[nimeratus]

Expected Behavior

Both of the costumes below produce the same highlight when the sprite thumbnail is clicked
Note that the highlight being 1 texel smaller than it should from all directions is a different bug, and it happens with more opaque costumes, too

Actual Behavior

One of the costumes has 0x0 highlight

Steps to Reproduce

Steps to reproduce the behavior:

1. Go to 'https://scratch.mit.edu/projects/1204399333/'
2. See inside
3. Click the sprite thumbnail
4. Switch to the other costume and click the thumbnail again

System Details

I've tested it on Windows 10, Chrome 138 but it probably happens on other systems, too

Screenshots
see above

[cwillisf]

I've heard that there are only two difficult things in programming:

• naming things
• cache coherence
• off-by-one errors

Seems like that's holding true here...