read_imagef and floating point coordinates, what's the range?

Hi,

Can I read/interpolate pixel values using floating point coordinates? Are the coordiantes [0…1] or [0…imagesize-1] if the sampler is not normalized? The following is not working for me

I have a 1x1x3 image3d with values [1,3,5] in memory. {CL_R, CL_FLOAT} image format.

__constant sampler_t sampler = CLK_NORMALIZED_COORDS_FALSE |
CLK_ADDRESS_CLAMP_TO_EDGE |
CLK_FILTER_LINEAR;

//WORKS and returns 3
myOutput = read_imagef(input, sampler, (int4)(0, 0, 1, 0)).x;
//DOESN’T WORK and returns 2, where is 2 from?
myOutput = read_imagef(input, sampler, (float4)(0, 0, 1, 0)).x;

Thanks.