Perfect resize lessons

[RudeGuy]

First of all, may this topic have to go in the help and support.
Second, you have to use the "image size" button and watch what height and widht have the NPC you want.

[Fuyu]

Do you mean giving custom sizes instead of the classical 32x32 and 64x64? Well, there's no actual way you can do it, at least not if you want it to look good. If you want to resize a certain sprite to a custom size, you'd rather do it manually.

If you mean resizing by the limits stipulated before there's a tool on Paint.NET that lets you change the size of your image. You'd rather want to turn the pixels on your image to 1x1 so right when you size it bigger it ends up being 2x2 pixelated. If you want to make it smaller, then turn them to 4x4 so when you size it smaller ends up being 2x2 as well.

NOTE: In case you don't know, to resize it on Paint.NET, go to Image/Change Size and select Nearest Neighbor. Right after that, change the size by using the percentage option (Set it to 50% if you want to make it smaller, or 200% if you want to make it bigger).

Hope this rather rushed explanation helped on any way.