How do people have smooth .bmp images?

[iR0]

I noticed UTAU voicebank icons retain a lot of detail and the character isn't pixelated. I'm trying to make an icon but the 100x100 pixels resolution needed for the .bmp file results in pixel art. How do you guys make high quality icons?

 

[Kiyoteru]

Draw at your normal full resolution first, then crop and resize.

 

[SaKe]

Draw at your normal full resolution first, then crop and resize.

Also, OpenUTAU lets you set an icon of any size, as long as it’s a square. It’ll only show in that program, though, not OG UTAU.
It also allows you to set transparent backgrounds, which can be kind of cool.