NAME
lqr_carver_bias_set_energy_function - set a custom energy function for
a LqrCarver object
SYNOPSIS
#include <lqr.h>
LqrRetVal lqr_carver_set_energy_function(LqrCarver* carver,
LqrEnergyFunc en_func,
gint radius,
LqrEnergyReaderType reader_type,
gpointer extra_data);
DESCRIPTION
The function lqr_carver_set_energy_function assigns the energy function
en_func to the LqrCarver object pointed to by carver (see below for
more details on custom functions definitions).
The parameter radius determines the size of the square region which
affects the computation around each pixel (the side of the square will
be 2 * radius + 1 pixels long).
The parameter reader_type sets the reader type used when reading the
image, and therefore it determines what quantity will be passed on to
the function en_func (see below for more details on reader types).
The parameter extra_data is a (void) pointer which can be used to pass
on additional values to the function ef_func.
CUSTOM FUNCTIONS DEFINITION
The function en_func must be of type LqrEnergyFunc, whose prototype is
defined by:
typedef gfloat (*LqrEnergyFunc) (gint x, gint y, gint img_width, gint img_height, LqrReadingWindow * rwindow, gpointer extra_data);
Such a function is expected to compute the energy at pixel x, y based
on the knowledge of the current image size (obtained from width and
height) and the content of the image in a square around that pixel,
which is passed through the rwindow reading window.
In most cases, the parameters x, y, width and height would only be used
to determine whether the region under consideration is at the image
boundary or not.
The rwindow content must be read using the function
lqr_rwindow_read(3).
READER TYPES
The LqrEnergyReaderType is an enum which can take these values (also
noted is the number of channels of the corresponging reading window):
LQR_ER_BRIGHTNESS
brightness (1 channel)
LQR_ER_BRIGHTNESS
luma (1 channel)
LQR_ER_RGBA
RGBA (4 channels)
LQR_ER_CUSTOM
read the normalised image channels as they are (as many channels as
the image has)
These readouts always return values beetween 0 and 1.
Note that these readouts may have special meanings depending on the
image type:
· for LQR_GREY_IMAGE, LQR_GREYA_IMAGE and LQR_CUSTOM_IMAGE images,
the LQR_ER_LUMA readout will yield the same result as
LQR_ER_BRIGHTNESS
· for LQR_CUSTOM_IMAGE images, the LQR_ER_BRIGHTNESS readout will
return the average pixel value (additive, i.e. if a black channel
is present the channel values will be inverted and multiplied by
the black channel inverse), multiplied by the alpha channel value.
· for LQR_CUSTOM_IMAGE images, the LQR_ER_RGBA readout cannot be
used: it will always return 0
RETURN VALUE
The return value follows the Liquid Rescale library signalling system.
SEE ALSO
lqr_carver_set_energy_function_builtin(3), lqr_carver_get_energy(3),
lqr_rwindow_read(3), lqr_rwindow_get_read_t(3),
lqr_rwindow_get_radius(3), lqr_rwindow_get_channels(3)
COPYRIGHT
Copyright © 2007-2009 Carlo Baldassi