java - how to know if the pixel color is black from a float 4 -


i ask question how know pixel color using t_sampler in jocl in different way want konw if pixel black or white knowing using t_sampler in kernel

const sampler_t smp = clk_normalized_coords_false | //natural coordinates                       clk_address_clamp | //clamp zeros                       clk_filter_nearest; //don't interpolate

then used 

int2 coord = (int2)(get_global_id(0), get_global_id(1));     float4 pixel = read_imageui(input, smp, coord);

my question is: how use value pixel know color of concerned pixel?

i stuck few days , tried many solutions solve problem, if need clarifications respond. here kernel code 

const sampler_t smp = clk_normalized_coords_false | //natural coordinates                       clk_address_clamp | //clamp zeros                       clk_filter_nearest; //don't interpolate __kernel void basic(__read_only image2d_t input,__global float *result)  {     int gidx = get_global_id(0);     int gidy = get_global_id(1);  int2 coord = (int2)(get_global_id(0), get_global_id(1));  int2 posin = {gidx, gidy};        float4 pixel = read_imagef(input, smp, posin); if ((pixel.x==0.0) && (pixel.y==0.0) && (pixel.z==0.0) ){  result[gidx]=1; }  else result[gidx]=0;     }

read pixel using read_imagef (i recommend instead of read_imageui, depending on image format, since in example assigning float4 variable; check specification appropriate each image format). float4 components returned can checked. pixel.x red, pixel.y green, pixel.z blue, , pixel.w alpha (1.0f if source format doesn't have alpha). check black (as ask in subject of question), check .x , .y , .z 0.0.


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