libsimdb/docs/usage.md

Library usage

Database know nothing about location of the source images, records addressed only by some numeric id.

Example usage:

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <simdb.h>

int main() {
  simdb_t *sdb = NULL;
  simdb_search_t search;
  simdb_match_t *match = NULL;
  const char *path = "/tmp/test.sdb";
  const char *files[] = {
    "/path/to/file/a.jpg",
    "/path/to/file/b.png",
    "/path/to/file/c.bmp",
  };
  int ret = 0;

  if (!simdb_create(path)) {
    perror("can't create test database");
    return 1;
  }

  sdb = simdb_open(path, SIMDB_FLAG_WRITE | SIMDB_FLAG_LOCKNB, &ret);
  if (!sdb) {
    fprintf(stderr, "can't open test simdb: %s\n", simdb_error(ret));
    return 1;
  }

  for (int i = 0; i < sizeof(files); i++) {
    ret = simdb_record_add(sdb, i, files[i], 0);
    if (ret < 0) {
      fprintf(stderr, "can't add file from %s: %s\n", files[i], simdb_error(ret));
    }
  }

  simdb_search_init(&search);
  /* tune search parameters */
  search.d_ratio  = 0.1;  /* max difference in ratio -- 10% */
  search.d_bitmap = 0.08; /* max difference in ratio --  8% */
  /* compare given file against database */
  const char *sample = "/path/to/file/d.png";
  simdb_search_file(sdb, &search, sample);
  /* show search results if any */
  if (search.found) {
    printf("file %s similar to:\n", sample);
    for (int i = 0; i < search.found; i++) {
      match = &search.matches[i];
      printf("- %s (%d %%)\n", files[match->num], (int) match->d_bitmap * 100);
    }
    /* free search results */
    simdb_search_free(&search);
  }

  simdb_close(sdb);
  unlink(path);

  return 0;
}

You may build this example with next command:

gcc -Wall -std=c99 -O0 -pedantic -lsimdb -o simdb-usage-test test.c