Currently on pg 238 of the 1.1 spec it says this: Determining
the border color If <addressing mode> in sampler is
CLK_ADDRESS_CLAMP, then out-of-range image coordinates return
the border color. The border color selected depends on the image
channel order and can be one of the following values: If the
image channel order is CL_A, CL_INTENSITY, CL_Rx, CL_RA, CL_RGx,
CL_RGBx, CL_ARGB, CL_BGRA, or CL_RGBA, the border color is
(0.0f, 0.0f, 0.0f, 0.0f). If the image channel order is CL_R,
CL_RG, CL_RGB, or CL_LUMINANCE, the border color is (0.0f, 0.0f,
0.0f, 1.0f I would like to see the ability to change the border
color added. All current GPUs support this in their hardware
(since OpenGL has it).  Currently I use the border color in my
kernel to handle out of range memory buffer accesss instead of
if/else as it is a lot cheaper.  Using zero works fine
currently, but it limits the kernel's flexibility for features I
want to add later on.