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quirc/lib/identify.c
Jaap Haitsma 2ff513b0b4 merge upstream
2021-06-16 23:52:51 -04:00

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/* quirc - QR-code recognition library
* Copyright (C) 2010-2012 Daniel Beer <dlbeer@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <limits.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <math.h>
#include "quirc_internal.h"
/************************************************************************
* Linear algebra routines
*/
static int line_intersect(const struct quirc_point *p0,
const struct quirc_point *p1,
const struct quirc_point *q0,
const struct quirc_point *q1,
struct quirc_point *r)
{
/* (a, b) is perpendicular to line p */
int a = -(p1->y - p0->y);
int b = p1->x - p0->x;
/* (c, d) is perpendicular to line q */
int c = -(q1->y - q0->y);
int d = q1->x - q0->x;
/* e and f are dot products of the respective vectors with p and q */
int e = a * p1->x + b * p1->y;
int f = c * q1->x + d * q1->y;
/* Now we need to solve:
* [a b] [rx] [e]
* [c d] [ry] = [f]
*
* We do this by inverting the matrix and applying it to (e, f):
* [ d -b] [e] [rx]
* 1/det [-c a] [f] = [ry]
*/
int det = (a * d) - (b * c);
if (!det)
return 0;
r->x = (d * e - b * f) / det;
r->y = (-c * e + a * f) / det;
return 1;
}
static void perspective_setup(double *c,
const struct quirc_point *rect,
double w, double h)
{
double x0 = rect[0].x;
double y0 = rect[0].y;
double x1 = rect[1].x;
double y1 = rect[1].y;
double x2 = rect[2].x;
double y2 = rect[2].y;
double x3 = rect[3].x;
double y3 = rect[3].y;
double wden = w * (x2*y3 - x3*y2 + (x3-x2)*y1 + x1*(y2-y3));
double hden = h * (x2*y3 + x1*(y2-y3) - x3*y2 + (x3-x2)*y1);
c[0] = (x1*(x2*y3-x3*y2) + x0*(-x2*y3+x3*y2+(x2-x3)*y1) +
x1*(x3-x2)*y0) / wden;
c[1] = -(x0*(x2*y3+x1*(y2-y3)-x2*y1) - x1*x3*y2 + x2*x3*y1
+ (x1*x3-x2*x3)*y0) / hden;
c[2] = x0;
c[3] = (y0*(x1*(y3-y2)-x2*y3+x3*y2) + y1*(x2*y3-x3*y2) +
x0*y1*(y2-y3)) / wden;
c[4] = (x0*(y1*y3-y2*y3) + x1*y2*y3 - x2*y1*y3 +
y0*(x3*y2-x1*y2+(x2-x3)*y1)) / hden;
c[5] = y0;
c[6] = (x1*(y3-y2) + x0*(y2-y3) + (x2-x3)*y1 + (x3-x2)*y0) / wden;
c[7] = (-x2*y3 + x1*y3 + x3*y2 + x0*(y1-y2) - x3*y1 + (x2-x1)*y0) /
hden;
}
static void perspective_map(const double *c,
double u, double v, struct quirc_point *ret)
{
double den = c[6]*u + c[7]*v + 1.0;
double x = (c[0]*u + c[1]*v + c[2]) / den;
double y = (c[3]*u + c[4]*v + c[5]) / den;
ret->x = (int) rint(x);
ret->y = (int) rint(y);
}
static void perspective_unmap(const double *c,
const struct quirc_point *in,
double *u, double *v)
{
double x = in->x;
double y = in->y;
double den = -c[0]*c[7]*y + c[1]*c[6]*y + (c[3]*c[7]-c[4]*c[6])*x +
c[0]*c[4] - c[1]*c[3];
*u = -(c[1]*(y-c[5]) - c[2]*c[7]*y + (c[5]*c[7]-c[4])*x + c[2]*c[4]) /
den;
*v = (c[0]*(y-c[5]) - c[2]*c[6]*y + (c[5]*c[6]-c[3])*x + c[2]*c[3]) /
den;
}
/************************************************************************
* Span-based floodfill routine
*/
typedef void (*span_func_t)(void *user_data, int y, int left, int right);
static void flood_fill_line(struct quirc *q, int x, int y,
int from, int to,
span_func_t func, void *user_data,
int *leftp, int *rightp)
{
quirc_pixel_t *row;
int left;
int right;
int i;
row = q->pixels + y * q->w;
QUIRC_ASSERT(row[x] == from);
left = x;
right = x;
while (left > 0 && row[left - 1] == from)
left--;
while (right < q->w - 1 && row[right + 1] == from)
right++;
/* Fill the extent */
for (i = left; i <= right; i++)
row[i] = to;
/* Return the processed range */
*leftp = left;
*rightp = right;
if (func)
func(user_data, y, left, right);
}
static struct quirc_flood_fill_vars *flood_fill_call_next(
struct quirc *q,
quirc_pixel_t *row,
int from, int to,
span_func_t func, void *user_data,
struct quirc_flood_fill_vars *vars,
int direction)
{
int *leftp;
if (direction < 0) {
leftp = &vars->left_up;
} else {
leftp = &vars->left_down;
}
while (*leftp <= vars->right) {
if (row[*leftp] == from) {
struct quirc_flood_fill_vars *next_vars;
int next_left;
/* Set up the next context */
next_vars = vars + 1;
next_vars->y = vars->y + direction;
/* Fill the extent */
flood_fill_line(q,
*leftp,
next_vars->y,
from, to,
func, user_data,
&next_left,
&next_vars->right);
next_vars->left_down = next_left;
next_vars->left_up = next_left;
return next_vars;
}
(*leftp)++;
}
return NULL;
}
static void flood_fill_seed(struct quirc *q,
int x0, int y0,
int from, int to,
span_func_t func, void *user_data)
{
struct quirc_flood_fill_vars *const stack = q->flood_fill_vars;
const size_t stack_size = q->num_flood_fill_vars;
const struct quirc_flood_fill_vars *const last_vars =
&stack[stack_size - 1];
QUIRC_ASSERT(from != to);
QUIRC_ASSERT(q->pixels[y0 * q->w + x0] == from);
struct quirc_flood_fill_vars *next_vars;
int next_left;
/* Set up the first context */
next_vars = stack;
next_vars->y = y0;
/* Fill the extent */
flood_fill_line(q, x0, next_vars->y, from, to,
func, user_data,
&next_left, &next_vars->right);
next_vars->left_down = next_left;
next_vars->left_up = next_left;
while (true) {
struct quirc_flood_fill_vars * const vars = next_vars;
quirc_pixel_t *row;
if (vars == last_vars) {
/*
* "Stack overflow".
* Just stop and return.
* This can be caused by very complex shapes in
* the image, which is not likely a part of
* a valid QR code anyway.
*/
break;
}
/* Seed new flood-fills */
if (vars->y > 0) {
row = q->pixels + (vars->y - 1) * q->w;
next_vars = flood_fill_call_next(q, row,
from, to,
func, user_data,
vars, -1);
if (next_vars != NULL) {
continue;
}
}
if (vars->y < q->h - 1) {
row = q->pixels + (vars->y + 1) * q->w;
next_vars = flood_fill_call_next(q, row,
from, to,
func, user_data,
vars, 1);
if (next_vars != NULL) {
continue;
}
}
if (vars > stack) {
/* Restore the previous context */
next_vars = vars - 1;
continue;
}
/* We've done. */
break;
}
}
/************************************************************************
* Adaptive thresholding
*/
static uint8_t otsu(const struct quirc *q)
{
unsigned int numPixels = q->w * q->h;
// Calculate histogram
unsigned int histogram[UINT8_MAX + 1];
(void)memset(histogram, 0, sizeof(histogram));
uint8_t* ptr = q->image;
unsigned int length = numPixels;
while (length--) {
uint8_t value = *ptr++;
histogram[value]++;
}
// Calculate weighted sum of histogram values
double sum = 0;
unsigned int i = 0;
for (i = 0; i <= UINT8_MAX; ++i) {
sum += i * histogram[i];
}
// Compute threshold
double sumB = 0;
unsigned int q1 = 0;
double max = 0;
uint8_t threshold = 0;
for (i = 0; i <= UINT8_MAX; ++i) {
// Weighted background
q1 += histogram[i];
if (q1 == 0)
continue;
// Weighted foreground
const unsigned int q2 = numPixels - q1;
if (q2 == 0)
break;
sumB += i * histogram[i];
const double m1 = sumB / q1;
const double m2 = (sum - sumB) / q2;
const double m1m2 = m1 - m2;
const double variance = m1m2 * m1m2 * q1 * q2;
if (variance >= max) {
threshold = i;
max = variance;
}
}
return threshold;
}
static void area_count(void *user_data, int y, int left, int right)
{
((struct quirc_region *)user_data)->count += right - left + 1;
}
static int region_code(struct quirc *q, int x, int y)
{
int pixel;
struct quirc_region *box;
int region;
if (x < 0 || y < 0 || x >= q->w || y >= q->h)
return -1;
pixel = q->pixels[y * q->w + x];
if (pixel >= QUIRC_PIXEL_REGION)
return pixel;
if (pixel == QUIRC_PIXEL_WHITE)
return -1;
if (q->num_regions >= QUIRC_MAX_REGIONS)
return -1;
region = q->num_regions;
box = &q->regions[q->num_regions++];
memset(box, 0, sizeof(*box));
box->seed.x = x;
box->seed.y = y;
box->capstone = -1;
flood_fill_seed(q, x, y, pixel, region, area_count, box);
return region;
}
struct polygon_score_data {
struct quirc_point ref;
int scores[4];
struct quirc_point *corners;
};
static void find_one_corner(void *user_data, int y, int left, int right)
{
struct polygon_score_data *psd =
(struct polygon_score_data *)user_data;
int xs[2] = {left, right};
int dy = y - psd->ref.y;
int i;
for (i = 0; i < 2; i++) {
int dx = xs[i] - psd->ref.x;
int d = dx * dx + dy * dy;
if (d > psd->scores[0]) {
psd->scores[0] = d;
psd->corners[0].x = xs[i];
psd->corners[0].y = y;
}
}
}
static void find_other_corners(void *user_data, int y, int left, int right)
{
struct polygon_score_data *psd =
(struct polygon_score_data *)user_data;
int xs[2] = {left, right};
int i;
for (i = 0; i < 2; i++) {
int up = xs[i] * psd->ref.x + y * psd->ref.y;
int right = xs[i] * -psd->ref.y + y * psd->ref.x;
int scores[4] = {up, right, -up, -right};
int j;
for (j = 0; j < 4; j++) {
if (scores[j] > psd->scores[j]) {
psd->scores[j] = scores[j];
psd->corners[j].x = xs[i];
psd->corners[j].y = y;
}
}
}
}
static void find_region_corners(struct quirc *q,
int rcode, const struct quirc_point *ref,
struct quirc_point *corners)
{
struct quirc_region *region = &q->regions[rcode];
struct polygon_score_data psd;
int i;
memset(&psd, 0, sizeof(psd));
psd.corners = corners;
memcpy(&psd.ref, ref, sizeof(psd.ref));
psd.scores[0] = -1;
flood_fill_seed(q, region->seed.x, region->seed.y,
rcode, QUIRC_PIXEL_BLACK,
find_one_corner, &psd);
psd.ref.x = psd.corners[0].x - psd.ref.x;
psd.ref.y = psd.corners[0].y - psd.ref.y;
for (i = 0; i < 4; i++)
memcpy(&psd.corners[i], &region->seed,
sizeof(psd.corners[i]));
i = region->seed.x * psd.ref.x + region->seed.y * psd.ref.y;
psd.scores[0] = i;
psd.scores[2] = -i;
i = region->seed.x * -psd.ref.y + region->seed.y * psd.ref.x;
psd.scores[1] = i;
psd.scores[3] = -i;
flood_fill_seed(q, region->seed.x, region->seed.y,
QUIRC_PIXEL_BLACK, rcode,
find_other_corners, &psd);
}
static void record_capstone(struct quirc *q, int ring, int stone)
{
struct quirc_region *stone_reg = &q->regions[stone];
struct quirc_region *ring_reg = &q->regions[ring];
struct quirc_capstone *capstone;
int cs_index;
if (q->num_capstones >= QUIRC_MAX_CAPSTONES)
return;
cs_index = q->num_capstones;
capstone = &q->capstones[q->num_capstones++];
memset(capstone, 0, sizeof(*capstone));
capstone->qr_grid = -1;
capstone->ring = ring;
capstone->stone = stone;
stone_reg->capstone = cs_index;
ring_reg->capstone = cs_index;
/* Find the corners of the ring */
find_region_corners(q, ring, &stone_reg->seed, capstone->corners);
/* Set up the perspective transform and find the center */
perspective_setup(capstone->c, capstone->corners, 7.0, 7.0);
perspective_map(capstone->c, 3.5, 3.5, &capstone->center);
}
static void test_capstone(struct quirc *q, unsigned int x, unsigned int y,
unsigned int *pb)
{
int ring_right = region_code(q, x - pb[4], y);
int stone = region_code(q, x - pb[4] - pb[3] - pb[2], y);
int ring_left = region_code(q, x - pb[4] - pb[3] -
pb[2] - pb[1] - pb[0],
y);
struct quirc_region *stone_reg;
struct quirc_region *ring_reg;
unsigned int ratio;
if (ring_left < 0 || ring_right < 0 || stone < 0)
return;
/* Left and ring of ring should be connected */
if (ring_left != ring_right)
return;
/* Ring should be disconnected from stone */
if (ring_left == stone)
return;
stone_reg = &q->regions[stone];
ring_reg = &q->regions[ring_left];
/* Already detected */
if (stone_reg->capstone >= 0 || ring_reg->capstone >= 0)
return;
/* Ratio should ideally be 37.5 */
ratio = stone_reg->count * 100 / ring_reg->count;
if (ratio < 10 || ratio > 70)
return;
record_capstone(q, ring_left, stone);
}
static void finder_scan(struct quirc *q, unsigned int y)
{
quirc_pixel_t *row = q->pixels + y * q->w;
unsigned int x;
int last_color = 0;
unsigned int run_length = 0;
unsigned int run_count = 0;
unsigned int pb[5];
memset(pb, 0, sizeof(pb));
for (x = 0; x < q->w; x++) {
int color = row[x] ? 1 : 0;
if (x && color != last_color) {
memmove(pb, pb + 1, sizeof(pb[0]) * 4);
pb[4] = run_length;
run_length = 0;
run_count++;
if (!color && run_count >= 5) {
const int scale = 16;
static const unsigned int check[5] = {1, 1, 3, 1, 1};
unsigned int avg, err;
unsigned int i;
int ok = 1;
avg = (pb[0] + pb[1] + pb[3] + pb[4]) * scale / 4;
err = avg * 3 / 4;
for (i = 0; i < 5; i++)
if (pb[i] * scale < check[i] * avg - err ||
pb[i] * scale > check[i] * avg + err)
ok = 0;
if (ok)
test_capstone(q, x, y, pb);
}
}
run_length++;
last_color = color;
}
}
static void find_alignment_pattern(struct quirc *q, int index)
{
struct quirc_grid *qr = &q->grids[index];
struct quirc_capstone *c0 = &q->capstones[qr->caps[0]];
struct quirc_capstone *c2 = &q->capstones[qr->caps[2]];
struct quirc_point a;
struct quirc_point b;
struct quirc_point c;
int size_estimate;
int step_size = 1;
int dir = 0;
double u, v;
/* Grab our previous estimate of the alignment pattern corner */
memcpy(&b, &qr->align, sizeof(b));
/* Guess another two corners of the alignment pattern so that we
* can estimate its size.
*/
perspective_unmap(c0->c, &b, &u, &v);
perspective_map(c0->c, u, v + 1.0, &a);
perspective_unmap(c2->c, &b, &u, &v);
perspective_map(c2->c, u + 1.0, v, &c);
size_estimate = abs((a.x - b.x) * -(c.y - b.y) +
(a.y - b.y) * (c.x - b.x));
/* Spiral outwards from the estimate point until we find something
* roughly the right size. Don't look too far from the estimate
* point.
*/
while (step_size * step_size < size_estimate * 100) {
static const int dx_map[] = {1, 0, -1, 0};
static const int dy_map[] = {0, -1, 0, 1};
int i;
for (i = 0; i < step_size; i++) {
int code = region_code(q, b.x, b.y);
if (code >= 0) {
struct quirc_region *reg = &q->regions[code];
if (reg->count >= size_estimate / 2 &&
reg->count <= size_estimate * 2) {
qr->align_region = code;
return;
}
}
b.x += dx_map[dir];
b.y += dy_map[dir];
}
dir = (dir + 1) % 4;
if (!(dir & 1))
step_size++;
}
}
static void find_leftmost_to_line(void *user_data, int y, int left, int right)
{
struct polygon_score_data *psd =
(struct polygon_score_data *)user_data;
int xs[2] = {left, right};
int i;
for (i = 0; i < 2; i++) {
int d = -psd->ref.y * xs[i] + psd->ref.x * y;
if (d < psd->scores[0]) {
psd->scores[0] = d;
psd->corners[0].x = xs[i];
psd->corners[0].y = y;
}
}
}
static double distance(struct quirc_point a, struct quirc_point b)
{
return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y));
}
/* Estimate grid size by determing distance between capstones
*/
static void measure_grid_size(struct quirc *q, int index)
{
struct quirc_grid *qr = &q->grids[index];
struct quirc_capstone *a = &(q->capstones[qr->caps[0]]);
struct quirc_capstone *b = &(q->capstones[qr->caps[1]]);
struct quirc_capstone *c = &(q->capstones[qr->caps[2]]);
double ab = distance(b->corners[0], a->corners[3]);
double capstone_ab_size = (distance(b->corners[0], b->corners[3]) + distance(a->corners[0], a->corners[3]))/2.0;
double ver_grid = 7.0 * ab / capstone_ab_size;
double bc = distance(b->corners[0], c->corners[1]);
double capstone_bc_size = (distance(b->corners[0], b->corners[1]) + distance(c->corners[0], c->corners[1]))/2.0;
double hor_grid = 7.0 * bc / capstone_bc_size;
double grid_size_estimate = (ver_grid + hor_grid) / 2;
qr->grid_size = 4*((int)(grid_size_estimate - 17.0 + 2.0) / 4) + 17;
}
/* Read a cell from a grid using the currently set perspective
* transform. Returns +/- 1 for black/white, 0 for cells which are
* out of image bounds.
*/
static int read_cell(const struct quirc *q, int index, int x, int y)
{
const struct quirc_grid *qr = &q->grids[index];
struct quirc_point p;
perspective_map(qr->c, x + 0.5, y + 0.5, &p);
if (p.y < 0 || p.y >= q->h || p.x < 0 || p.x >= q->w)
return 0;
return q->pixels[p.y * q->w + p.x] ? 1 : -1;
}
static int fitness_cell(const struct quirc *q, int index, int x, int y)
{
const struct quirc_grid *qr = &q->grids[index];
int score = 0;
int u, v;
for (v = 0; v < 3; v++)
for (u = 0; u < 3; u++) {
static const double offsets[] = {0.3, 0.5, 0.7};
struct quirc_point p;
perspective_map(qr->c, x + offsets[u],
y + offsets[v], &p);
if (p.y < 0 || p.y >= q->h || p.x < 0 || p.x >= q->w)
continue;
if (q->pixels[p.y * q->w + p.x])
score++;
else
score--;
}
return score;
}
static int fitness_ring(const struct quirc *q, int index, int cx, int cy,
int radius)
{
int i;
int score = 0;
for (i = 0; i < radius * 2; i++) {
score += fitness_cell(q, index, cx - radius + i, cy - radius);
score += fitness_cell(q, index, cx - radius, cy + radius - i);
score += fitness_cell(q, index, cx + radius, cy - radius + i);
score += fitness_cell(q, index, cx + radius - i, cy + radius);
}
return score;
}
static int fitness_apat(const struct quirc *q, int index, int cx, int cy)
{
return fitness_cell(q, index, cx, cy) -
fitness_ring(q, index, cx, cy, 1) +
fitness_ring(q, index, cx, cy, 2);
}
static int fitness_capstone(const struct quirc *q, int index, int x, int y)
{
x += 3;
y += 3;
return fitness_cell(q, index, x, y) +
fitness_ring(q, index, x, y, 1) -
fitness_ring(q, index, x, y, 2) +
fitness_ring(q, index, x, y, 3);
}
/* Compute a fitness score for the currently configured perspective
* transform, using the features we expect to find by scanning the
* grid.
*/
static int fitness_all(const struct quirc *q, int index)
{
const struct quirc_grid *qr = &q->grids[index];
int version = (qr->grid_size - 17) / 4;
const struct quirc_version_info *info = &quirc_version_db[version];
int score = 0;
int i, j;
int ap_count;
/* Check the timing pattern */
for (i = 0; i < qr->grid_size - 14; i++) {
int expect = (i & 1) ? 1 : -1;
score += fitness_cell(q, index, i + 7, 6) * expect;
score += fitness_cell(q, index, 6, i + 7) * expect;
}
/* Check capstones */
score += fitness_capstone(q, index, 0, 0);
score += fitness_capstone(q, index, qr->grid_size - 7, 0);
score += fitness_capstone(q, index, 0, qr->grid_size - 7);
if (version < 0 || version > QUIRC_MAX_VERSION)
return score;
/* Check alignment patterns */
ap_count = 0;
while ((ap_count < QUIRC_MAX_ALIGNMENT) && info->apat[ap_count])
ap_count++;
for (i = 1; i + 1 < ap_count; i++) {
score += fitness_apat(q, index, 6, info->apat[i]);
score += fitness_apat(q, index, info->apat[i], 6);
}
for (i = 1; i < ap_count; i++)
for (j = 1; j < ap_count; j++)
score += fitness_apat(q, index,
info->apat[i], info->apat[j]);
return score;
}
static void jiggle_perspective(struct quirc *q, int index)
{
struct quirc_grid *qr = &q->grids[index];
int best = fitness_all(q, index);
int pass;
double adjustments[8];
int i;
for (i = 0; i < 8; i++)
adjustments[i] = qr->c[i] * 0.02;
for (pass = 0; pass < 5; pass++) {
for (i = 0; i < 16; i++) {
int j = i >> 1;
int test;
double old = qr->c[j];
double step = adjustments[j];
double new;
if (i & 1)
new = old + step;
else
new = old - step;
qr->c[j] = new;
test = fitness_all(q, index);
if (test > best)
best = test;
else
qr->c[j] = old;
}
for (i = 0; i < 8; i++)
adjustments[i] *= 0.5;
}
}
/* Once the capstones are in place and an alignment point has been
* chosen, we call this function to set up a grid-reading perspective
* transform.
*/
static void setup_qr_perspective(struct quirc *q, int index)
{
struct quirc_grid *qr = &q->grids[index];
struct quirc_point rect[4];
/* Set up the perspective map for reading the grid */
memcpy(&rect[0], &q->capstones[qr->caps[1]].corners[0],
sizeof(rect[0]));
memcpy(&rect[1], &q->capstones[qr->caps[2]].corners[0],
sizeof(rect[0]));
memcpy(&rect[2], &qr->align, sizeof(rect[0]));
memcpy(&rect[3], &q->capstones[qr->caps[0]].corners[0],
sizeof(rect[0]));
perspective_setup(qr->c, rect, qr->grid_size - 7, qr->grid_size - 7);
jiggle_perspective(q, index);
}
/* Rotate the capstone with so that corner 0 is the leftmost with respect
* to the given reference line.
*/
static void rotate_capstone(struct quirc_capstone *cap,
const struct quirc_point *h0,
const struct quirc_point *hd)
{
struct quirc_point copy[4];
int j;
int best = 0;
int best_score = INT_MAX;
for (j = 0; j < 4; j++) {
struct quirc_point *p = &cap->corners[j];
int score = (p->x - h0->x) * -hd->y +
(p->y - h0->y) * hd->x;
if (!j || score < best_score) {
best = j;
best_score = score;
}
}
/* Rotate the capstone */
for (j = 0; j < 4; j++)
memcpy(&copy[j], &cap->corners[(j + best) % 4],
sizeof(copy[j]));
memcpy(cap->corners, copy, sizeof(cap->corners));
perspective_setup(cap->c, cap->corners, 7.0, 7.0);
}
static void record_qr_grid(struct quirc *q, int a, int b, int c)
{
struct quirc_point h0, hd;
int i;
int qr_index;
struct quirc_grid *qr;
if (q->num_grids >= QUIRC_MAX_GRIDS)
return;
/* Construct the hypotenuse line from A to C. B should be to
* the left of this line.
*/
memcpy(&h0, &q->capstones[a].center, sizeof(h0));
hd.x = q->capstones[c].center.x - q->capstones[a].center.x;
hd.y = q->capstones[c].center.y - q->capstones[a].center.y;
/* Make sure A-B-C is clockwise */
if ((q->capstones[b].center.x - h0.x) * -hd.y +
(q->capstones[b].center.y - h0.y) * hd.x > 0) {
int swap = a;
a = c;
c = swap;
hd.x = -hd.x;
hd.y = -hd.y;
}
/* Record the grid and its components */
qr_index = q->num_grids;
qr = &q->grids[q->num_grids++];
memset(qr, 0, sizeof(*qr));
qr->caps[0] = a;
qr->caps[1] = b;
qr->caps[2] = c;
qr->align_region = -1;
/* Rotate each capstone so that corner 0 is top-left with respect
* to the grid.
*/
for (i = 0; i < 3; i++) {
struct quirc_capstone *cap = &q->capstones[qr->caps[i]];
rotate_capstone(cap, &h0, &hd);
cap->qr_grid = qr_index;
}
/* Check the timing pattern by measuring grid size. This doesn't require a perspective
* transform.
*/
measure_grid_size(q, qr_index);
/* Make an estimate based for the alignment pattern based on extending
* lines from capstones A and C.
*/
if (!line_intersect(&q->capstones[a].corners[0],
&q->capstones[a].corners[1],
&q->capstones[c].corners[0],
&q->capstones[c].corners[3],
&qr->align))
goto fail;
/* On V2+ grids, we should use the alignment pattern. */
if (qr->grid_size > 21) {
/* Try to find the actual location of the alignment pattern. */
find_alignment_pattern(q, qr_index);
/* Find the point of the alignment pattern closest to the
* top-left of the QR grid.
*/
if (qr->align_region >= 0) {
struct polygon_score_data psd;
struct quirc_region *reg =
&q->regions[qr->align_region];
/* Start from some point inside the alignment pattern */
memcpy(&qr->align, &reg->seed, sizeof(qr->align));
memcpy(&psd.ref, &hd, sizeof(psd.ref));
psd.corners = &qr->align;
psd.scores[0] = -hd.y * qr->align.x +
hd.x * qr->align.y;
flood_fill_seed(q, reg->seed.x, reg->seed.y,
qr->align_region, QUIRC_PIXEL_BLACK,
NULL, NULL);
flood_fill_seed(q, reg->seed.x, reg->seed.y,
QUIRC_PIXEL_BLACK, qr->align_region,
find_leftmost_to_line, &psd);
}
}
setup_qr_perspective(q, qr_index);
return;
fail:
/* We've been unable to complete setup for this grid. Undo what we've
* recorded and pretend it never happened.
*/
for (i = 0; i < 3; i++)
q->capstones[qr->caps[i]].qr_grid = -1;
q->num_grids--;
}
struct neighbour {
int index;
double distance;
};
struct neighbour_list {
struct neighbour n[QUIRC_MAX_CAPSTONES];
int count;
};
static void test_neighbours(struct quirc *q, int i,
const struct neighbour_list *hlist,
const struct neighbour_list *vlist)
{
/* Test each possible grouping */
for (int j = 0; j < hlist->count; j++) {
const struct neighbour *hn = &hlist->n[j];
for (int k = 0; k < vlist->count; k++) {
const struct neighbour *vn = &vlist->n[k];
double squareness = fabs(1.0 - hn->distance / vn->distance);
if (squareness < 0.2)
record_qr_grid(q, hn->index, i, vn->index);
}
}
}
static void test_grouping(struct quirc *q, unsigned int i)
{
struct quirc_capstone *c1 = &q->capstones[i];
int j;
struct neighbour_list hlist;
struct neighbour_list vlist;
hlist.count = 0;
vlist.count = 0;
/* Look for potential neighbours by examining the relative gradients
* from this capstone to others.
*/
for (j = 0; j < q->num_capstones; j++) {
struct quirc_capstone *c2 = &q->capstones[j];
double u, v;
if (i == j)
continue;
perspective_unmap(c1->c, &c2->center, &u, &v);
u = fabs(u - 3.5);
v = fabs(v - 3.5);
if (u < 0.2 * v) {
struct neighbour *n = &hlist.n[hlist.count++];
n->index = j;
n->distance = v;
}
if (v < 0.2 * u) {
struct neighbour *n = &vlist.n[vlist.count++];
n->index = j;
n->distance = u;
}
}
if (!(hlist.count && vlist.count))
return;
test_neighbours(q, i, &hlist, &vlist);
}
static void pixels_setup(struct quirc *q, uint8_t threshold)
{
if (QUIRC_PIXEL_ALIAS_IMAGE) {
q->pixels = (quirc_pixel_t *)q->image;
}
uint8_t* source = q->image;
quirc_pixel_t* dest = q->pixels;
int length = q->w * q->h;
while (length--) {
uint8_t value = *source++;
*dest++ = (value < threshold) ? QUIRC_PIXEL_BLACK : QUIRC_PIXEL_WHITE;
}
}
uint8_t *quirc_begin(struct quirc *q, int *w, int *h)
{
q->num_regions = QUIRC_PIXEL_REGION;
q->num_capstones = 0;
q->num_grids = 0;
if (w)
*w = q->w;
if (h)
*h = q->h;
return q->image;
}
void quirc_end(struct quirc *q)
{
int i;
uint8_t threshold = otsu(q);
pixels_setup(q, threshold);
for (i = 0; i < q->h; i++)
finder_scan(q, i);
for (i = 0; i < q->num_capstones; i++)
test_grouping(q, i);
}
void quirc_extract(const struct quirc *q, int index,
struct quirc_code *code)
{
const struct quirc_grid *qr = &q->grids[index];
int y;
int i = 0;
if (index < 0 || index > q->num_grids)
return;
memset(code, 0, sizeof(*code));
perspective_map(qr->c, 0.0, 0.0, &code->corners[0]);
perspective_map(qr->c, qr->grid_size, 0.0, &code->corners[1]);
perspective_map(qr->c, qr->grid_size, qr->grid_size,
&code->corners[2]);
perspective_map(qr->c, 0.0, qr->grid_size, &code->corners[3]);
code->size = qr->grid_size;
for (y = 0; y < qr->grid_size; y++) {
int x;
for (x = 0; x < qr->grid_size; x++) {
if (read_cell(q, index, x, y) > 0) {
code->cell_bitmap[i >> 3] |= (1 << (i & 7));
}
i++;
}
}
}
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