[fprint] compare fp_print_data

Dawit Abate dawitabate2 at gmail.com
Sat Jun 24 11:44:12 UTC 2017

I have been trying to implement fingerprint identification by getting
fp_print_data from the device once and compare it with files on the
database. But i have a problem with fpi_img_compare_print_data. It returns
-22 - Invalid print format. I explicitly removed the check condition in
img.c and it takes too much time to compute. And I don't think it is
returning a valid value. I don't know where I am missing.

here is the code.

int main(int argc, char * argv[]) {

        struct fp_dscv_dev ** discv_devs = NULL; /* list of scanners */
        struct fp_dscv_dev * using_dev = NULL; /* using device */
        struct fp_dev * dev = NULL;
        struct fp_print_data * print_data = NULL; /* fingerprint from base
        struct fp_print_data * print_image = NULL; /* fingerprint from file
        int verify_retval = 0;
        gchar *path;

        /* init library fprint */
        if (fp_init()) {
                fprintf(stderr, "Cannit init fprint library!\n");
                return 1;

        // get list of devices
        discv_devs = fp_discover_devs();
        if (!discv_devs) {
                fprintf(stderr, "Cannot discover any fingerprint
                return 1;

        // use first found device and print driver's name
        using_dev = discv_devs[0];
        printf("Found device using %s driver.\n",
        if ((dev = fp_dev_open(using_dev)) == NULL) {
                fprintf(stderr, "Could not open device\n");
                return 1;

        printf("Enter the path to file 1:\n");
        int data1;
        scanf("%d", &data1);

        /* Load finger print from base */
        printf("Loading first print\n");
        if (fp_print_data_load(dev, user_id1, &print_data)) {
                fprintf(stderr, "Failed to load the first fingerprint\n");
                return 1;

        printf("Enter the path to file 1:\n");
        int data2;
        scanf("%d", &data2);

        /* Load fingerprint from file */
        printf("Loading second print\n");
        if (fp_print_data_load(dev, 2, &print_image)) {
                fprintf(stderr, "Failed to load the second fingerprint\n");
                return 1;

        int match_score;

        match_score = fpi_img_compare_print_data (print_data, print_data);
        if (match_score > 40){
                printf("Not Matched\n");
        printf("Score = %d\n", match_score);

        // free resources


        return 0;
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