81 lines
3.5 KiB
Common Lisp
81 lines
3.5 KiB
Common Lisp
// Copyright (C) 2021 Majid Geravand
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// Copyright (C) 2021 Gfuse
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__kernel void fast_gray(
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__read_only image2d_t image,
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__global int2 * corners,
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__global int * icorner,
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int fast_count
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) {
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// Prepare a suitable OpenCL image sampler.
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sampler_t const sampler = CLK_ADDRESS_CLAMP | CLK_FILTER_NEAREST;
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// Use global work item as 2D image coordinates.
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int const x = get_global_id(0);
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int const y = get_global_id(1);
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if(x>16 && x<get_image_width(image)-16 && y<get_image_height(image)-16 && y>16){
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int2 const xy = (int2)(x, y);
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// Read the candidate pixel.
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int const p00 = read_imageui(image, sampler, xy).x;
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// Read other pixels in a circle around the candidate pixel.
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int const p01 = read_imageui(image, sampler, xy + (int2)( 0, 3)).x;
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int const p05 = read_imageui(image, sampler, xy + (int2)( 3, 0)).x;
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int const p09 = read_imageui(image, sampler, xy + (int2)( 0, -3)).x;
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int const p13 = read_imageui(image, sampler, xy + (int2)(-3, 0)).x;
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// Check the absolute difference of each circle pixel.
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int const d01 = (abs(p01 - p00) > FAST_THRESH);
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int const d05 = (abs(p05 - p00) > FAST_THRESH);
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int const d09 = (abs(p09 - p00) > FAST_THRESH);
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int const d13 = (abs(p13 - p00) > FAST_THRESH);
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// Check if any two adjacent circle pixels have a high absolute difference.
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if ((d01 && d05) ||(d05 && d09) ||(d09 && d13) ||(d13 && d01)) {
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// Read other pixels in a circle around the candidate pixel.
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int const p02 = read_imageui(image, sampler, xy + (int2)( 1, 3)).x;
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int const p03 = read_imageui(image, sampler, xy + (int2)( 2, 2)).x;
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int const p04 = read_imageui(image, sampler, xy + (int2)( 3, 1)).x;
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int const p06 = read_imageui(image, sampler, xy + (int2)( 3, -1)).x;
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int const p07 = read_imageui(image, sampler, xy + (int2)( 2, -2)).x;
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int const p08 = read_imageui(image, sampler, xy + (int2)( 1, -3)).x;
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int const p10 = read_imageui(image, sampler, xy + (int2)(-1, -3)).x;
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int const p11 = read_imageui(image, sampler, xy + (int2)(-2, -2)).x;
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int const p12 = read_imageui(image, sampler, xy + (int2)(-3, -1)).x;
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int const p14 = read_imageui(image, sampler, xy + (int2)(-3, 1)).x;
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int const p15 = read_imageui(image, sampler, xy + (int2)(-2, 2)).x;
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int const p16 = read_imageui(image, sampler, xy + (int2)(-1, 3)).x;
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// Select the maximum score.
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int sco = p00;
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sco = max(sco, p01);
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sco = max(sco, p02);
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sco = max(sco, p03);
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sco = max(sco, p04);
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sco = max(sco, p05);
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sco = max(sco, p06);
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sco = max(sco, p07);
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sco = max(sco, p08);
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sco = max(sco, p09);
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sco = max(sco, p10);
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sco = max(sco, p11);
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sco = max(sco, p12);
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sco = max(sco, p13);
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sco = max(sco, p14);
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sco = max(sco, p15);
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// Keep this score if it is as good as the maximum.
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if (p00 >= sco) {
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// Atomically append to corner buffer.
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int const icorn = atom_inc(icorner);
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if (icorn < fast_count)
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corners[icorn] = xy;
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}
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}
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}
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}
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