fpi_std_sq_dev ()

gint
fpi_std_sq_dev (const guint8 *buf,
                gint size);

Calculates the squared standard deviation of the individual pixels in the buffer, as per the following formula:

1
2

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.

fpi_mean_sq_diff_norm ()

gint
fpi_mean_sq_diff_norm (const guint8 *buf1,
                       const guint8 *buf2,
                       gint size);

This function calculates the normalized mean square difference of two buffers, usually two lines, as per the following formula:

1

sq_diff = sum ((buf1[0..size] - buf2[0..size]) ^ 2) / size

This functions is usually used to get numerical difference between two images.

fpi_image_resize ()

FpImage *
fpi_image_resize (FpImage *orig,
                  guint w_factor,
                  guint h_factor);

enum FpiImageFlags

Flags used in an FpImage structure to describe the contained image. This is useful for image drivers as they can simply set these flags and rely on the image to be normalized by libfprint before further processing.

FpImage

typedef struct {
  guint         width;
  guint         height;

  gdouble       ppmm;

  FpiImageFlags flags;
} FpImage;

Structure holding an image. The public fields are only public for internal use by the drivers.

The “height” property

  “height”                   guint

The height of the image.

Owner: FpImage

Flags: Read / Write / Construct Only

Allowed values: <= 65535

Default value: 0

The “width” property

  “width”                    guint

The width of the image.

Owner: FpImage

Flags: Read / Write / Construct Only

Allowed values: <= 65535

Default value: 0