@Faymir and the others:
I'll quickly explain why i suggest to delete(or only resize if the skins is absolutly not available anymore):
Imagine a 2x2 Grid that contains our skin
Top Left is the body, what do you do if you get a 3x3 Pixels Image, and want to draw the top left body now?
Thats problem number 1, see image below
The second is that sampling(the process of bringing your texture to the screen) doesnt work in pixels but in a coordinate system from 0 to 1, where 0 is the MOST left and 1 the MOST right of your texture =>
you do not hit the center of a pixel but the most left of the pixel. To prevent that you add an offset(half of the pixel), but this offset obviously is bigger on a smaller resolution. So a higher resolution will create less of this offset, and that causes the image to scale:
math:
a 4x4 texture adds (1/4)/2 offset(half of a pixel), that is 0.125 in float
a 8x8 texture adds (1/8)/2 offset(half of a pixel), that is 0.0625 in float
so the coordinate system isnt correct at this point anymore(since its normalized) [btw using a constant offset doesnt work bcs of mipmaps, which causes texture bleeding, but i wont go into details^^]
Also adding an offset at all, already modifies the texture size, so its better to clamp the values instead
so split your 4x4 texture into 2x2 piecies to fit our imagination skin system
then you have a single 2x2 texture for your body and can clamp the edges to the mid of the texture, which makes in highly accurate.
You see its quite complicated, but meditory to have it working correctly for higher resolutions, without any bugs, even if you dont see the bugs in ur 4k skin(btw there is no gain viewing this 4k version on ur Full HD monitor)
Lastly, if it loads slower, it might be bcs of internal resizing to minimize the above explained stuff (edited)