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/* This file is part of MyPaint.
* Copyright (C) 2018 by the MyPaint Development Team.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include "gap_detection.hpp"
DistanceBucket::DistanceBucket(int distance) : distance(distance)
{
int r = N + distance * 2 + 2;
input = new chan_t*[r];
for (int i = 0; i < r; ++i)
input[i] = new chan_t[r];
}
DistanceBucket::~DistanceBucket()
{
int r = N + distance * 2 + 2;
for (int i = 0; i < r; ++i)
delete[] input[i];
delete[] input;
}
static inline void
upd_dist(coord lc, PixelBuffer<chan_t>& dists, int new_dst)
{
if (lc.x < 0 || lc.x > (N - 1) || lc.y < 0 || lc.y > (N - 1)) return;
int curr_dist = dists(lc.x, lc.y);
if (curr_dist > new_dst) {
dists(lc.x, lc.y) = new_dst;
}
}
using rot_op = std::function<coord(int x, int y, int x_offset, int y_offset)>;
// Search an octant with a radius of _dist_ pixels, marking any gaps
// that are found. The octant searched is determined by the rotation
// function provided.
bool
dist_search(
int x, int y, int dist, chan_t** alphas, PixelBuffer<chan_t>& dists,
rot_op op)
{
// int d_lim = 1 + (dist * dist);
int offs = dist + 1;
int rx = x - offs;
int ry = y - offs;
coord t1 = op(x, y, 0, -1);
coord t2 = op(x, y, 1, -1);
if (alphas[t1.y][t1.x] == 0 || alphas[t2.y][t2.x] == 0) return false;
bool gap_found = false;
for (int yoffs = 2; yoffs < dist + 2; ++yoffs) {
int y_dst_sqr = (yoffs - 1) * (yoffs - 1);
for (int xoffs = 0; xoffs <= yoffs; ++xoffs) {
int offs_dst = y_dst_sqr + (xoffs) * (xoffs);
if (offs_dst >= 1 + dist * dist) break;
coord c = op(x, y, xoffs, -yoffs);
if (alphas[c.y][c.x] == 0) {
// Gap found
gap_found = true;
// Double-width distance assignment
float dx = (float)xoffs / (yoffs - 1);
float tx = 0;
int cx = 0;
for (int cy = 1; cy < yoffs; ++cy) {
upd_dist(op(rx, ry, cx, 0 - cy), dists, offs_dst);
tx += dx;
if (floor(tx) > cx) {
cx++;
upd_dist(op(rx, ry, cx, 0 - cy), dists, offs_dst);
}
upd_dist(op(rx, ry, cx + 1, 0 - cy), dists, offs_dst);
}
}
}
}
return gap_found;
}
// Coordinate reflection/rotation
coord
top_right(int x, int y, int x_offset, int y_offset)
{
return coord(x + x_offset, y + y_offset);
}
coord
top_centr(int x, int y, int x_offset, int y_offset)
{
return coord(x - y_offset, y - x_offset);
}
coord
bot_centr(int x, int y, int x_offset, int y_offset)
{
return coord(x - y_offset, y + x_offset);
}
coord
bot_right(int x, int y, int x_offset, int y_offset)
{
return coord(x + x_offset, y - y_offset);
}
/* Search for gaps in the 9-grid of flooded alpha tiles,
a gap being defined as a
*/
bool
find_gaps(
DistanceBucket& rb, PyObject* radiuses_arr, PyObject* mid, PyObject* n,
PyObject* e, PyObject* s, PyObject* w, PyObject* ne, PyObject* se,
PyObject* sw, PyObject* nw)
{
int r = rb.distance + 1;
typedef PixelBuffer<chan_t> PBT;
GridVector input{PBT(nw), PBT(n), PBT(ne), PBT(w), PBT(mid),
PBT(e), PBT(se), PBT(s), PBT(sw)};
init_from_nine_grid(r, rb.input, false, input);
bool gaps_found = false;
PixelBuffer<chan_t> radiuses(radiuses_arr);
// search for gaps in an approximate semi-circle
for (int y = 0; y < 2 * r + N - 1;
++y) { // we check at most distance+1 pixels above any point
for (int x = 0; x < r + N - 1; ++x) {
if (rb.input[y][x] ==
0) { // Search for gaps in relation to this pixel
if (y >= r) {
gaps_found |= dist_search(
x, y, rb.distance, rb.input, radiuses, top_right);
gaps_found |= dist_search(
x, y, rb.distance, rb.input, radiuses, top_centr);
}
if (y < N + r) {
gaps_found |= dist_search(
x, y, rb.distance, rb.input, radiuses, bot_centr);
gaps_found |= dist_search(
x, y, rb.distance, rb.input, radiuses, bot_right);
}
}
}
}
return gaps_found;
}
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