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fastimagehash.cpp
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fastimagehash.cpp
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#include "fastimagehash.h"
#include <iostream>
#include <opencv2/opencv.hpp>
#include <wavelib.h>
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <fftw3.h>
#include <sys/stat.h>
static void init() __attribute__((constructor));
void init() {
fftw_make_planner_thread_safe();
}
using namespace cv;
#define FASTIMAGEHASH_OK 0
#define FASTIMAGEHASH_READ_ERR -2
#define FASTIMAGEHASH_DECODE_ERR -3
__always_inline
double median(double *arr, size_t len) {
std::sort(arr, arr + len);
if (len % 2 == 0) {
return (arr[(len / 2) - 1] + arr[len / 2]) / 2;
} else {
return arr[(len + 1 / 2)];
}
}
__always_inline
double median(uchar *arr, size_t len) {
std::sort(arr, arr + len);
if (len % 2 == 0) {
return (double) (arr[(len / 2) - 1] + arr[len / 2]) / 2;
} else {
return arr[(len + 1 / 2)];
}
}
void hash_to_hex_string(const uchar *h, char *out, int hash_size) {
int hash_len = hash_size * hash_size / 4;
for (unsigned int i = 0; i < hash_len; i += 2) {
sprintf(out + i, "%02x", h[i / 2]);
}
out[hash_len + 1] = '\0';
}
void hash_to_hex_string_reversed(const uchar *h, char *out, int hash_size) {
int hash_len = hash_size * hash_size / 4;
for (unsigned int i = 0; i < hash_len; i += 2) {
uchar c = (h[i / 2] & 0x80) >> 7 |
(h[i / 2] & 0x40) >> 5 |
(h[i / 2] & 0x20) >> 3 |
(h[i / 2] & 0x10) >> 1 |
(h[i / 2] & 0x08) << 1 |
(h[i / 2] & 0x04) << 3 |
(h[i / 2] & 0x02) << 5 |
(h[i / 2] & 0x01) << 7;
sprintf(out + i, "%02x", c);
}
out[hash_len + 1] = '\0';
}
__always_inline
void set_bit_at(uchar *buf, unsigned int offset, bool val) {
unsigned int byte_offset = offset / 8;
unsigned int bit_offset = offset - byte_offset * 8;
if (val) {
buf[byte_offset] |= (1 << bit_offset);
} else {
buf[byte_offset] &= ~(1 << bit_offset);
}
}
void *load_file_in_mem(const char *filepath, size_t *size) {
struct stat info{};
if (stat(filepath, &info) != 0) {
return nullptr;
}
FILE *file = fopen(filepath, "rb");
if (file == nullptr) {
return nullptr;
}
void *buf = malloc(info.st_size);
size_t _ = fread(buf, sizeof(char), info.st_size, file);
*size = info.st_size;
return buf;
}
int ahash_file(const char *filepath, uchar *out, int hash_size) {
size_t size;
void *buf = load_file_in_mem(filepath, &size);
if (buf == nullptr) {
return FASTIMAGEHASH_READ_ERR;
}
int ret = ahash_mem(buf, size, out, hash_size);
free(buf);
return ret;
}
int ahash_mem(void *buf, size_t buf_len, uchar *out, int hash_size) {
Mat im;
try {
im = imdecode(Mat(1, buf_len, CV_8UC1, buf), IMREAD_GRAYSCALE);
resize(im, im, Size(hash_size, hash_size), 0, 0, INTER_AREA);
} catch (Exception &e) {
return FASTIMAGEHASH_DECODE_ERR;
}
double avg = mean(im).val[0];
uchar *pixel = im.ptr(0);
int endPixel = im.cols * im.rows;
for (int i = 0; i < endPixel; i++) {
set_bit_at(out, i, pixel[i] > avg);
}
return FASTIMAGEHASH_OK;
}
int mhash_file(const char *filepath, uchar *out, int hash_size) {
size_t size;
void *buf = load_file_in_mem(filepath, &size);
if (buf == nullptr) {
return FASTIMAGEHASH_READ_ERR;
}
int ret = mhash_mem(buf, size, out, hash_size);
free(buf);
return ret;
}
int mhash_mem(void *buf, size_t buf_len, uchar *out, int hash_size) {
Mat im;
try {
im = imdecode(Mat(1, buf_len, CV_8UC1, buf), IMREAD_GRAYSCALE);
resize(im, im, Size(hash_size, hash_size), 0, 0, INTER_AREA);
} catch (Exception &e) {
return FASTIMAGEHASH_DECODE_ERR;
}
uchar *pixel = im.ptr(0);
const int endPixel = im.cols * im.rows;
uchar sorted[im.cols * im.rows];
memcpy(sorted, pixel, endPixel);
double med = median(sorted, endPixel);
for (int i = 0; i < endPixel; i++) {
set_bit_at(out, i, pixel[i] > med);
}
return FASTIMAGEHASH_OK;
}
int dhash_file(const char *filepath, uchar *out, int hash_size) {
size_t size;
void *buf = load_file_in_mem(filepath, &size);
if (buf == nullptr) {
return FASTIMAGEHASH_READ_ERR;
}
int ret = dhash_mem(buf, size, out, hash_size);
free(buf);
return ret;
}
int dhash_mem(void *buf, size_t buf_len, uchar *out, int hash_size) {
Mat im;
try {
im = imdecode(Mat(1, buf_len, CV_8UC1, buf), IMREAD_GRAYSCALE);
resize(im, im, Size(hash_size + 1, hash_size), 0, 0, INTER_AREA);
} catch (Exception &e) {
return FASTIMAGEHASH_DECODE_ERR;
}
int offset = 0;
for (int i = 0; i < im.rows; ++i) {
uchar *pixel = im.ptr(i);
for (int j = 1; j < im.cols; ++j) {
set_bit_at(out, offset++, pixel[j] > pixel[j - 1]);
}
}
return FASTIMAGEHASH_OK;
}
int whash_file(const char *filepath, uchar *out, int hash_size, int img_scale, int remove_max_ll, const char *wname) {
size_t size;
void *buf = load_file_in_mem(filepath, &size);
if (buf == nullptr) {
return FASTIMAGEHASH_READ_ERR;
}
int ret = whash_mem(buf, size, out, hash_size, img_scale, remove_max_ll, wname);
free(buf);
return ret;
}
int whash_mem(void *buf, size_t buf_len, uchar *out, const int hash_size, int img_scale, int remove_max_ll,
const char *wname) {
Mat im;
try {
im = imdecode(Mat(1, buf_len, CV_8UC1, buf), IMREAD_GRAYSCALE);
} catch (Exception &e) {
return FASTIMAGEHASH_DECODE_ERR;
}
if (strcmp(wname, "haar") != 0 && strcmp(wname, "db4") != 0) {
throw std::invalid_argument("wname must be either of 'haar' or 'db4'");
}
if ((hash_size & (hash_size - 1)) != 0) {
throw std::invalid_argument("hash_size must be a power of two");
}
if (img_scale != 0) {
if ((img_scale & (img_scale - 1)) != 0) {
throw std::invalid_argument("img_scale must be a power of two");
}
} else {
int image_natural_scale = (int) pow(2, (int) log2(MIN(im.rows, im.cols)));
img_scale = MAX(image_natural_scale, hash_size);
}
int ll_max_level = (int) log2(img_scale);
int level = (int) log2(hash_size);
if (ll_max_level < level) {
throw std::invalid_argument("hash_size in a wrong range");
}
int dwt_level = ll_max_level - level;
if (dwt_level < 1) {
dwt_level = 1;
}
try {
resize(im, im, Size(img_scale, img_scale), 0, 0, INTER_AREA);
} catch (Exception &e) {
return FASTIMAGEHASH_DECODE_ERR;
}
auto data = (double *) malloc(img_scale * img_scale * sizeof(double));
uchar *pixel = im.ptr(0);
const int endPixel = im.cols * im.rows;
for (int i = 0; i < endPixel; i++) {
data[i] = (double) pixel[i] / 255;
}
if (remove_max_ll) {
// Remove low level frequency
wave_object w_haar_tmp = wave_init("haar");
int max_level = (int) (log((double) img_scale / ((double) w_haar_tmp->filtlength - 1.0)) / log(2.0));
ll_max_level = MIN(ll_max_level, max_level);
wt2_object wt_haar_tmp = wt2_init(w_haar_tmp, "dwt", img_scale, img_scale, ll_max_level);
double *coeffs = dwt2(wt_haar_tmp, data);
coeffs[0] = 0;
idwt2(wt_haar_tmp, coeffs, data);
wt2_free(wt_haar_tmp);
wave_free(w_haar_tmp);
free(coeffs);
}
wave_object w = wave_init(wname);
wt2_object wt = wt2_init(w, "dwt", img_scale, img_scale, dwt_level);
double *coeffs = dwt2(wt, data);
double sorted[hash_size * hash_size];
memcpy(sorted, coeffs, sizeof(double) * hash_size * hash_size);
double med = median(sorted, hash_size * hash_size);
for (int i = 0; i < hash_size * hash_size; ++i) {
set_bit_at(out, i, coeffs[i] > med);
}
free(data);
wt2_free(wt);
wave_free(w);
free(coeffs);
return FASTIMAGEHASH_OK;
}
int phash_file(const char *filepath, uchar *out, const int hash_size, int highfreq_factor) {
size_t size;
void *buf = load_file_in_mem(filepath, &size);
if (buf == nullptr) {
return FASTIMAGEHASH_READ_ERR;
}
int ret = phash_mem(buf, size, out, hash_size, highfreq_factor);
free(buf);
return ret;
}
int phash_mem(void *buf, size_t buf_len, uchar *out, const int hash_size, int highfreq_factor) {
int img_size = hash_size * highfreq_factor;
Mat im;
try {
im = imdecode(Mat(1, buf_len, CV_8UC1, buf), IMREAD_GRAYSCALE);
resize(im, im, Size(img_size, img_size), 0, 0, INTER_AREA);
} catch (Exception &e) {
return FASTIMAGEHASH_DECODE_ERR;
}
double pixels[img_size * img_size];
uchar *pixel = im.ptr(0);
int endPixel = im.cols * im.rows;
for (int i = 0; i < endPixel; i++) {
pixels[i] = (double) pixel[i] / 255;
}
double dct_out[img_size * img_size];
fftw_plan plan = fftw_plan_r2r_2d(
img_size, img_size,
pixels, dct_out,
FFTW_REDFT10, FFTW_REDFT10, // DCT-II
FFTW_ESTIMATE
);
fftw_execute(plan);
fftw_destroy_plan(plan);
double dct_lowfreq[hash_size * hash_size];
double sorted[hash_size * hash_size];
int ptr_low = 0;
int ptr = 0;
for (int i = 0; i < hash_size; ++i) {
for (int j = 0; j < hash_size; ++j) {
dct_lowfreq[ptr_low] = dct_out[ptr];
sorted[ptr_low] = dct_out[ptr];
ptr_low += 1;
ptr += 1;
}
ptr += (img_size - hash_size);
}
double med = median(sorted, hash_size * hash_size);
for (int i = 0; i < hash_size * hash_size; ++i) {
set_bit_at(out, i, dct_lowfreq[i] > med);
}
return FASTIMAGEHASH_OK;
}