NAME
im_dilate, im_dilate_raw, im_erode, im_erode_raw - perform
morphological operations on a white object against a black background
SYNOPSIS
#include <vips/vips.h>
int im_dilate(in, out, m)
IMAGE *in, *out;
INTMASK *m;
int im_erode(in, out, m)
IMAGE *in, *out;
INTMASK *m;
int im_dilate_raw(in, out, m)
IMAGE *in, *out;
INTMASK *m;
int im_erode_raw(in, out, m)
IMAGE *in, *out;
INTMASK *m;
DESCRIPTION
The above functions are applications of morphological operations on one
channel binary images ie. images with pixels that are either 0 (black)
or 255 (white). All functions assume that input images contain white
objects against a black background.
Mask coefficients can be either 0 (for object) or 255 (for background)
or 128 (for do not care).
The mask should have odd length sides and the origin of the mask is at
location (m->xsize/2,m->ysize/2) integer division. All algorithms have
been based on the book "Fundamentals of Digital Image Processing" by A.
Jain, pp 384-388, Prentice-Hall, 1989. Essentially, im_dilate(3) sets
pixels in the output if *any* part of the mask matches, whereas
im_erode(3) sets pixels only if *all* of the mask matches.
im_dilate(3) dilates the image pointed by in, according to the mask
pointed by m and writes the result in the location pointed by the IMAGE
descriptor out. The output image is the same size as the input, in the
manner of im_conv(3).
im_dilate_raw(3) works as im_dilate(3), but does not expand the input.
im_erode(3) erodes the image pointed by in, according to the mask
pointed by m and writes the result in the location pointed by the IMAGE
descriptor out. Again, the output image is forced to have the same size
as the input.
im_erode_raw(3) works as im_erode(3), but does not expand the input.
See the boolean operations im_andimage(3), im_orimage(3) and
im_eorimage(3) for analogues of the usual set difference and set union
operations.
RETURN VALUE
All functions returns 0 on success and -1 on error.
SEE ALSO
im_read_imask(3), im_conv(3), im_andimage(3), im_rotate_imask(3).
COPYRIGHT
1991-1995, Birkbeck College and the National Gallery
14 May 1991