libfprint/libfprint/fpi-image.c
Benjamin Berg 07ff03970f libfprint: Fix a few issues with the documentation
This must have been broken all along. Get it into a better shape. Looks
like mostly cases of bad copy/paste.
2020-05-11 20:51:29 +02:00

149 lines
4.2 KiB
C

/*
* FPrint Image - Private APIs
* Copyright (C) 2007 Daniel Drake <dsd@gentoo.org>
* Copyright (C) 2019 Benjamin Berg <bberg@redhat.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#define FP_COMPONENT "image"
#include "fpi-image.h"
#include "fpi-log.h"
#include <nbis.h>
#if HAVE_PIXMAN
#include <pixman.h>
#endif
/**
* SECTION: fpi-image
* @title: Internal FpImage
* @short_description: Internal image handling routines
*
* Internal image handling routines. See #FpImage for public routines.
*/
/**
* fpi_std_sq_dev:
* @buf: buffer (usually bitmap, one byte per pixel)
* @size: size of @buffer
*
* Calculates the squared standard deviation of the individual
* pixels in the buffer, as per the following formula:
* |[<!-- -->
* mean = sum (buf[0..size]) / size
* sq_dev = sum ((buf[0.size] - mean) ^ 2)
* ]|
* This function is usually used to determine whether image
* is empty.
*
* Returns: the squared standard deviation for @buffer
*/
gint
fpi_std_sq_dev (const guint8 *buf,
gint size)
{
guint64 res = 0, mean = 0;
gint i;
for (i = 0; i < size; i++)
mean += buf[i];
mean /= size;
for (i = 0; i < size; i++)
{
int dev = (int) buf[i] - mean;
res += dev * dev;
}
return res / size;
}
/**
* fpi_mean_sq_diff_norm:
* @buf1: buffer (usually bitmap, one byte per pixel)
* @buf2: buffer (usually bitmap, one byte per pixel)
* @size: buffer size of smallest buffer
*
* This function calculates the normalized mean square difference of
* two buffers, usually two lines, as per the following formula:
* |[<!-- -->
* sq_diff = sum ((buf1[0..size] - buf2[0..size]) ^ 2) / size
* ]|
*
* This functions is usually used to get numerical difference
* between two images.
*
* Returns: the normalized mean squared difference between @buf1 and @buf2
*/
gint
fpi_mean_sq_diff_norm (const guint8 *buf1,
const guint8 *buf2,
gint size)
{
int res = 0, i;
for (i = 0; i < size; i++)
{
int dev = (int) buf1[i] - (int) buf2[i];
res += dev * dev;
}
return res / size;
}
#if HAVE_PIXMAN
FpImage *
fpi_image_resize (FpImage *orig_img,
guint w_factor,
guint h_factor)
{
int new_width = orig_img->width * w_factor;
int new_height = orig_img->height * h_factor;
pixman_image_t *orig, *resized;
pixman_transform_t transform;
FpImage *newimg;
orig = pixman_image_create_bits (PIXMAN_a8, orig_img->width, orig_img->height, (uint32_t *) orig_img->data, orig_img->width);
resized = pixman_image_create_bits (PIXMAN_a8, new_width, new_height, NULL, new_width);
pixman_transform_init_identity (&transform);
pixman_transform_scale (NULL, &transform, pixman_int_to_fixed (w_factor), pixman_int_to_fixed (h_factor));
pixman_image_set_transform (orig, &transform);
pixman_image_set_filter (orig, PIXMAN_FILTER_BILINEAR, NULL, 0);
pixman_image_composite32 (PIXMAN_OP_SRC,
orig, /* src */
NULL, /* mask */
resized, /* dst */
0, 0, /* src x y */
0, 0, /* mask x y */
0, 0, /* dst x y */
new_width, new_height /* width height */
);
newimg = fp_image_new (new_width, new_height);
newimg->flags = orig_img->flags;
memcpy (newimg->data, pixman_image_get_data (resized), new_width * new_height);
pixman_image_unref (orig);
pixman_image_unref (resized);
return newimg;
}
#endif