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/*
* function: kernel_gauss
* input: image2d_t as read only
* output: image2d_t as write only
* workitem = 4x2 pixel ouptut
* GAUSS_RADIUS must be defined in build options.
*/
#ifndef GAUSS_RADIUS
#define GAUSS_RADIUS 2
#endif
#define GAUSS_SCALE (2 * GAUSS_RADIUS + 1)
__kernel void kernel_gauss (__read_only image2d_t input, __write_only image2d_t output, __global float *table)
{
int x = get_global_id (0);
int y = get_global_id (1);
sampler_t sampler = CLK_NORMALIZED_COORDS_FALSE | CLK_ADDRESS_CLAMP_TO_EDGE | CLK_FILTER_NEAREST;
float4 in1;
int i, j;
int index;
float4 out1 = (float4)(0.0f, 0.0f, 0.0f, 0.0f);
float4 out2 = (float4)(0.0f, 0.0f, 0.0f, 0.0f);
for(i = 0; i < GAUSS_SCALE + 1; i++)
for(j = 0; j < GAUSS_SCALE + 3; j++) {
in1 = read_imagef (input, sampler, (int2)(4 * x - GAUSS_RADIUS + j, 2 * y - GAUSS_RADIUS + i));
//first line
if (i < GAUSS_SCALE) {
index = i * GAUSS_SCALE + j;
out1.x += (j < GAUSS_SCALE ? table[index] * in1.x : 0.0f);
index -= 1;
out1.y += ((j < GAUSS_SCALE + 1) && j > 0 ? table[index] * in1.x : 0.0f);
index -= 1;
out1.z += ((j < GAUSS_SCALE + 2) && j > 1 ? table[index] * in1.x : 0.0f);
index -= 1;
out1.w += (j > 2 ? table[index] * in1.x : 0.0f);
}
//second line
if (i > 0) {
index = (i - 1) * GAUSS_SCALE + j;
out2.x += (j < GAUSS_SCALE ? table[index] * in1.x : 0.0f);
index -= 1;
out2.y += ((j < GAUSS_SCALE + 1) && j > 0 ? table[index] * in1.x : 0.0f);
index -= 1;
out2.z += ((j < GAUSS_SCALE + 2) && j > 1 ? table[index] * in1.x : 0.0f);
index -= 1;
out2.w += (j > 2 ? table[index] * in1.x : 0.0f);
}
}
write_imagef(output, (int2)(x, 2 * y), out1);
write_imagef(output, (int2)(x, 2 * y + 1), out2);
}
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