.\"     Title: \fBlqr_carver_set_energy_function\fR
.\"    Author: Carlo Baldassi
.\" Generator: DocBook XSL Stylesheets v1.73.2 <http://docbook.sf.net/>
.\"      Date: 10 Maj 2009
.\"    Manual: LqR library API reference
.\"    Source: LqR library 0.4.1 API (3:1:3)
.\"
.TH "\FBLQR_CARVER_SET_ENERGY_FUNCT" "3" "10 Maj 2009" "LqR library 0.4.1 API (3:1:3)" "LqR library API reference"
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.SH "NAME"
lqr_carver_bias_set_energy_function \- set a custom energy function for a LqrCarver object
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <lqr\&.h>
.fi
.ft
.HP 41
.BI "LqrRetVal lqr_carver_set_energy_function(LqrCarver*\ " "carver" ", LqrEnergyFunc\ " "en_func" ", gint\ " "radius" ", LqrEnergyReaderType\ " "reader_type" ", gpointer\ " "extra_data" ");"
.SH "DESCRIPTION"
.PP
The function
\fBlqr_carver_set_energy_function\fR
assigns the energy function
\fIen_func\fR
to the
LqrCarver
object pointed to by
\fIcarver\fR
(see below for more details on custom functions definitions)\&.
.PP
The parameter
\fIradius\fR
determines the size of the square region which affects the computation around each pixel (the side of the square will be
2 * \fIradius\fR + 1
pixels long)\&.
.PP
The parameter
\fIreader_type\fR
sets the reader type used when reading the image, and therefore it determines what quantity will be passed on to the function
\fIen_func\fR
(see below for more details on reader types)\&.
.PP
The parameter
\fIextra_data\fR
is a (void) pointer which can be used to pass on additional values to the function
\fIef_func\fR\&.
.SH "CUSTOM FUNCTIONS DEFINITION"
.PP
The function
\fIen_func\fR
must be of type
LqrEnergyFunc, whose prototype is defined by:
.sp
.RS 4
.nf
typedef gfloat (*LqrEnergyFunc) (gint x, gint y, gint img_width, gint img_height, LqrReadingWindow * rwindow, gpointer extra_data);
                        
.fi
.RE
.sp
Such a function is expected to compute the energy at pixel
\fIx\fR,
\fIy\fR
based on the knowledge of the current image size (obtained from
\fIwidth\fR
and
\fIheight\fR) and the content of the image in a square around that pixel, which is passed through the
\fIrwindow\fR
reading window\&.
.PP
In most cases, the parameters
\fIx\fR,
\fIy\fR,
\fIwidth\fR
and
\fIheight\fR
would only be used to determine whether the region under consideration is at the image boundary or not\&.
.PP
The
\fIrwindow\fR
content must be read using the function
\fBlqr_rwindow_read\fR(3)\&.
.SH "READER TYPES"
.PP
The
\fBLqrEnergyReaderType\fR
is an enum which can take these values (also noted is the number of channels of the corresponging reading window):
.PP
LQR_ER_BRIGHTNESS
.RS 4
brightness (1 channel)
.RE
.PP
LQR_ER_BRIGHTNESS
.RS 4
luma (1 channel)
.RE
.PP
LQR_ER_RGBA
.RS 4
RGBA (4 channels)
.RE
.PP
LQR_ER_CUSTOM
.RS 4
read the normalised image channels as they are (as many channels as the image has)
.RE
These readouts always return values beetween
0
and
1\&.
.PP
Note that these readouts may have special meanings depending on the image type:
.sp
.RS 4
\h'-04'\(bu\h'+03'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
.RE
.sp
.RS 4
\h'-04'\(bu\h'+03'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\&.
.RE
.sp
.RS 4
\h'-04'\(bu\h'+03'for
LQR_CUSTOM_IMAGE
images, the
LQR_ER_RGBA
readout
\fIcannot be used\fR: it will always return
0
.RE
.sp
.RE
.SH "RETURN VALUE"
.PP
The return value follows the Liquid Rescale library signalling system\&.
.SH "SEE ALSO"
.PP

\fBlqr_carver_set_energy_function_builtin\fR(3), \fBlqr_carver_get_energy\fR(3), \fBlqr_rwindow_read\fR(3), \fBlqr_rwindow_get_read_t\fR(3), \fBlqr_rwindow_get_radius\fR(3), \fBlqr_rwindow_get_channels\fR(3)
.SH "COPYRIGHT"
Copyright \(co 2007-2009 Carlo Baldassi
.br