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Merge pull request #103 from yamt/otsu

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Fix possible overflows in otsu()
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Daniel Beer 2021-05-11 13:24:56 +12:00 committed by GitHub
commit c6fc67088a
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1 changed files with 8 additions and 8 deletions
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16
lib/identify.c
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@ -177,28 +177,28 @@ static void flood_fill_seed(struct quirc *q, int x, int y, int from, int to,
static uint8_t otsu(const struct quirc *q) static uint8_t otsu(const struct quirc *q)
{ {
int numPixels = q->w * q->h; unsigned int numPixels = q->w * q->h;
// Calculate histogram // Calculate histogram
unsigned int histogram[UINT8_MAX + 1]; unsigned int histogram[UINT8_MAX + 1];
(void)memset(histogram, 0, sizeof(histogram)); (void)memset(histogram, 0, sizeof(histogram));
uint8_t* ptr = q->image; uint8_t* ptr = q->image;
int length = numPixels; unsigned int length = numPixels;
while (length--) { while (length--) {
uint8_t value = *ptr++; uint8_t value = *ptr++;
histogram[value]++; histogram[value]++;
} }
// Calculate weighted sum of histogram values // Calculate weighted sum of histogram values
unsigned int sum = 0; double sum = 0;
unsigned int i = 0; unsigned int i = 0;
for (i = 0; i <= UINT8_MAX; ++i) { for (i = 0; i <= UINT8_MAX; ++i) {
sum += i * histogram[i]; sum += i * histogram[i];
} }
// Compute threshold // Compute threshold
int sumB = 0; double sumB = 0;
int q1 = 0; unsigned int q1 = 0;
double max = 0; double max = 0;
uint8_t threshold = 0; uint8_t threshold = 0;
for (i = 0; i <= UINT8_MAX; ++i) { for (i = 0; i <= UINT8_MAX; ++i) {
@ -208,13 +208,13 @@ static uint8_t otsu(const struct quirc *q)
continue; continue;
// Weighted foreground // Weighted foreground
const int q2 = numPixels - q1; const unsigned int q2 = numPixels - q1;
if (q2 == 0) if (q2 == 0)
break; break;
sumB += i * histogram[i]; sumB += i * histogram[i];
const double m1 = (double)sumB / q1; const double m1 = sumB / q1;
const double m2 = ((double)sum - sumB) / q2; const double m2 = (sum - sumB) / q2;
const double m1m2 = m1 - m2; const double m1m2 = m1 - m2;
const double variance = m1m2 * m1m2 * q1 * q2; const double variance = m1m2 * m1m2 * q1 * q2;
if (variance >= max) { if (variance >= max) {