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.