For what I have tested, this is not enough. You need to also skip the central pixel position otherwise you will always detect a local maxima on border with no maxima around:

input      output
0 0 0      1 0 0
0 0 0  ->  0 0 0
0 0 0      0 0 0

more here :

• Detect Maxima/Minima border effect bug #23

To make it clean, I now save the pixel position needed

const int4 centerPos = (int4){x,y,z,0};            // central pixel position saved before loop
int4 localPos = localMaxPos + (int4){rx,ry,rz,0};  // local pixel position being evaluated in the loop

and I use the OpenCL integrated function any and all to test if vectors are equals as such:

if( all(localPos >= 0) && any(localPos != centerPos) )

I only fixed the detect_maxima.cl so far but the rest is in the to do list.

Also, not sure relevant for your side for now, but you may want to add a cast to float when initializing localMin/Max value

float localMax = READ_src_IMAGE(src, sampler, pos).x - 1;

into

float localMax = (float) READ_src_IMAGE(src, sampler, pos).x - 1;

otherwise it will fail for unsigned type inputs as the -1 will apply before the float conversion.