NAME
lqr_carver_rigmask_add_xy, lqr_carver_rigmask_add_area,
lqr_carver_rigmask_add, lqr_carver_rigmask_add_rgb_area,
lqr_carver_rigmask_add_rgb - update an LqrCarver rigidity mask
SYNOPSIS
#include <lqr.h>
LqrRetVal lqr_carver_rigmask_add_xy(LqrCarver* carver,
gdouble rigidity, gint x, gint y);
LqrRetVal lqr_carver_rigmask_add_area(LqrCarver* carver,
gdouble* buffer, gint width,
gint height, gint x_off,
gint y_off);
LqrRetVal lqr_carver_rigmask_add(LqrCarver* carver, gdouble* buffer);
LqrRetVal lqr_carver_rigmask_add_area(LqrCarver* carver,
gdouble* buffer, gint channels,
gint width, gint height,
gint x_off, gint y_off);
LqrRetVal lqr_carver_rigmask_add_rgb(LqrCarver* carver,
gdouble* buffer, gint channels);
FOREWORD
All the functions described in this page are used to add a rigidity
mask to LqrCarver objects. Whenever one of these functions is called, a
rigidity mask is activated for the whole image; the mask contains
coefficients which modulate the value of the rigidity (which is set
with lqr_carver_init(3)) in different areas of the image.
It is very important to note that using no rigidity masks at all is
equivalent to use a rigidity mask over the whole image with all the
values set to 1.0, but, when first adding a rigidity mask to a
LqrCarver object, all the pixels outside the affected area will have
their rigidity set to zero; therefore, the functions
lqr_carver_rigmask_add_xy, lqr_carver_rigmask_add_area and
lqr_carver_rigmask_add_rgb_area actually affect the whole image,
despite their name.
All the functions must be called after lqr_carver_init and before
lqr_carver_resize. If called multiple times over the same area, new
values will replace the old ones.
SETTING THE RIGIDITY MASK PIXEL BY PIXEL
The function lqr_carver_rigmask_add_xy sets the rigidity mask value of
the x, y pixel of the image loaded into the LqrCarver object pointed to
by carver
SETTING THE RIGIDITY MASK FROM A BUFFER
The function lqr_carver_rigmask_add_area adds a rigidity mask to an
area of the image loaded in the LqrCarver object pointed to by carver.
The parameter buffer must point to an array of doubles of size width *
height, ordered first by rows, then by columns.
The offset of the area relative to the image are specified through
x_off and y_off. The rigidity mask area can exceed the boundary of the
image, and the offsets can be negative.
The values in the given buffer are scaled by the overall rigidity value
set when calling the function lqr_carver_init.
The function lqr_carver_rigmask_add can be used when the area to add is
of the same size of the image loaded in the LqrCarver object and the
offsets are 0.
SETTING THE RIGIDITY MASK FROM AN IMAGE
The functions lqr_carver_rigmask_add_rgb_area and
lqr_carver_rigmask_add_rgb are very similar to
lqr_carver_rigmask_add_area and lqr_carver_rigmask_add, but use 8-bit
multi-channel images as inputs.
The number of channels in the image is passed via the parameter
channels. The last channel is assumed to be the alpha (opacity) channel
if channels is equal to 2 or greater than 3 (if this is not the case,
use the previous functions).
The rigidity value is computed from the average of the colour channels,
multiplied by the value of the alpha channel if present. For example,
in RGBA images a white, nontransparent pixel is equivalent to a value
of 1.0 when using a buffer in lqr_carver_rigmask_add_area.
RETURN VALUE
The return values follow the Liquid Rescale library signalling system.
SEE ALSO
LqrRetVal(3), lqr_carver_init(3), lqr_carver_bias_add(3)
COPYRIGHT
Copyright © 2007-2009 Carlo Baldassi