Importing UV-Maps with blender

Hello, i recently write a script for importing a 3d modell in blender. this modell also have uv coords. but there is a problem. the texturesize is 256 x 256. the uv-maps are not in 0.5; 0.75 form. the form i had is in pixel. so 0.5 can be 127 or 128. 0.75 = 192 pixel. if i try to calculate the pixel data in points i get a problem. the texture on the faces is no more exactly shown. is it possible to import the pixel data direct with pyton? i had another problem too. if i made a new modell and i want to add the uv coords i cannot add them directly in fields (such as U: 0.5 V: 0) is there a chance to add the data with number in the uv mapping editor? i need exact entrys for the uv maps. Thank you very much for your help Oxygene