texturing coordinates issuse


i have a texture 256 * 512 pixels big
but i would like to UV map a specific pixel
point to the vertex, but problem is here,
because UV mapping is done with floating point numbers from 0.0 to 1.0

i know pixel position and image size,
how do i calculate the actual uv “friendly”

say you want (10,100).

10 * (1.0f / 512),100 * (1.0f / 256)
or simplier 10/512,100/256