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