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/*
* Copyright (C) 2014-2017 Karlsruhe Institute of Technology
*
* This file is part of Ufo.
*
* This library is free software: you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, either
* version 3 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef BOX_SIZE
#define BOX_SIZE 3
#endif
kernel void
filter (global float *input,
global float *output,
const float o_threshold,
const int o_sign)
{
const int HALF_SIZE = (BOX_SIZE - 1) / 2;
const int ARR_SIZE = BOX_SIZE * BOX_SIZE;
int idx = get_global_id(0);
int idy = get_global_id(1);
int width = get_global_size(0);
int height = get_global_size(1);
/* Check for boundary elements */
if (idy < HALF_SIZE || idy + HALF_SIZE >= height || idx < HALF_SIZE || idx + HALF_SIZE >= width)
output[idy * width + idx] = input[idy * width + idx];
else {
float elements[BOX_SIZE * BOX_SIZE];
/* Start at top left corner and pull out data */
/* int index = (idy - HALF_SIZE) * width + idx - HALF_SIZE; */
int i = 0;
for (int y = idy - HALF_SIZE; y < idy + HALF_SIZE + 1; y++) {
for (int x = idx - HALF_SIZE; x < idx + HALF_SIZE + 1; x++) {
elements[i++] = input[y * width + x];
}
}
/* Sort elements with (for now) insertion sort */
for (int i = 1; i < ARR_SIZE; i++) {
int j = i;
while (j > 0 && elements[j-1] > elements[j]) {
float tmp = elements[j-1];
elements[j-1] = elements[j];
elements[j] = tmp;
j--;
}
}
if (input[idy * width + idx]*o_sign > elements[(ARR_SIZE - 1)/ 2]*o_sign + o_threshold) {
float median_unbiased = ( elements[(ARR_SIZE - 1) / 2] + elements[(ARR_SIZE - 1) / 2 - o_sign] ) / 2 ;
output[idy * width + idx] = (float)(median_unbiased);
}
else {
output[idy * width + idx] = input[idy * width + idx];
}
}
}
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