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