picom/src/kernel.c

122 lines
2.8 KiB
C

// SPDX-License-Identifier: MPL-2.0
// Copyright (c) Yuxuan Shui <yshuiv7@gmail.com>
#include <math.h>
#include "kernel.h"
#include "utils.h"
/*
* A picture will help
*
* -center 0 width width+center
* -center +-----+-------------------+-----+
* | | | |
* | | | |
* 0 +-----+-------------------+-----+
* | | | |
* | | | |
* | | | |
* height +-----+-------------------+-----+
* | | | |
* height+ | | | |
* center +-----+-------------------+-----+
*/
double sum_kernel(const conv *map, int x, int y, int width,
int height) {
int fx, fy;
const double *g_data;
const double *g_line = map->data;
int g_size = map->size;
int center = g_size / 2;
int fx_start, fx_end;
int fy_start, fy_end;
double v;
/*
* Compute set of filter values which are "in range",
* that's the set with:
* 0 <= x + (fx-center) && x + (fx-center) < width &&
* 0 <= y + (fy-center) && y + (fy-center) < height
*
* 0 <= x + (fx - center) x + fx - center < width
* center - x <= fx fx < width + center - x
*/
fx_start = center - x;
if (fx_start < 0)
fx_start = 0;
fx_end = width + center - x;
if (fx_end > g_size)
fx_end = g_size;
fy_start = center - y;
if (fy_start < 0)
fy_start = 0;
fy_end = height + center - y;
if (fy_end > g_size)
fy_end = g_size;
g_line = g_line + fy_start * g_size + fx_start;
v = 0;
for (fy = fy_start; fy < fy_end; fy++) {
g_data = g_line;
g_line += g_size;
for (fx = fx_start; fx < fx_end; fx++) {
v += *g_data++;
}
}
if (v > 1)
v = 1;
return v;
}
static double attr_const gaussian(double r, double x, double y) {
// Formula can be found here:
// https://en.wikipedia.org/wiki/Gaussian_blur#Mathematics
// Except a special case for r == 0 to produce sharp shadows
if (r == 0)
return 1;
return exp(-0.5 * (x * x + y * y) / (r * r)) / (2 * M_PI * r * r);
}
conv *gaussian_kernel(double r) {
conv *c;
int size = r * 2 + 1;
int center = size / 2;
double t;
c = cvalloc(sizeof(conv) + size * size * sizeof(double));
c->size = size;
t = 0.0;
/*printf_errf("(): %f", r);*/
for (int y = 0; y < size; y++) {
for (int x = 0; x < size; x++) {
double g = gaussian(r, x - center, y - center);
t += g;
c->data[y * size + x] = g;
/*printf("%f ", c->data[y*size+x]);*/
}
/*printf("\n");*/
}
for (int y = 0; y < size; y++) {
for (int x = 0; x < size; x++) {
c->data[y * size + x] /= t;
/*printf("%f ", c->data[y*size+x]);*/
}
/*printf("\n");*/
}
return c;
}
// vim: set noet sw=8 ts=8 :