Erode image
IM2 = imerode(IM,SE)
IM2 = imerode(IM,NHOOD)
IM2 = imerode(___,PACKOPT,M)
IM2 = imerode(___,SHAPE)
gpuarrayIM2 = imerode(gpuarrayIM,___)
IM2 = imerode(IM,SE)
erodes the grayscale,
binary, or packed binary image IM
, returning the
eroded image IM2
. The argument SE
is
a structuring element object or array of structuring element objects
returned by the strel
or offsetstrel
functions.
If IM
is logical and the structuring element
is flat, imerode
performs binary erosion; otherwise
it performs grayscale erosion. If SE
is an array
of structuring element objects, imerode
performs
multiple erosions of the input image, using each structuring element
in SE
in succession.
IM2 = imerode(IM,NHOOD)
erodes the image IM
,
where NHOOD
is an array of 0
's
and 1
's that specifies the structuring element
neighborhood. This is equivalent to the syntax imerode(IM,strel(NHOOD))
.
The imerode
function determines the center element
of the neighborhood by floor((size(NHOOD)+1)/2)
.
IM2 = imerode(___,PACKOPT,M)
specifies
whether IM
is a packed binary image and, if it
is, provides the row dimension M
of the original
unpacked image. PACKOPT
can have either of the
following values. Default value is enclosed in braces ({}
).
Value  Description 





If PACKOPT
is 'ispacked'
,
you must specify a value for M
.
IM2 = imerode(___,SHAPE)
specifies
the size of the output image. SHAPE
can have either
of the following values. Default value is enclosed in braces ({}
).
Value  Description 

 Make the output image the same size as the input image.
If the value of 
 Compute the full erosion. 
gpuarrayIM2 = imerode(gpuarrayIM,___)
performs
the operation on a graphics processing unit (GPU). gpuarrayIM
is
a gpuArray
that contains a grayscale or binary
image. gpuarrayIM2
is a gpuArray
of
the same class as the input image. Note that the PACKOPT
syntax
is not supported on a GPU. This syntax requires the Parallel Computing Toolbox™.
Code Generation support: Yes.
MATLAB Function Block support: Yes.
IM
can be numeric or logical and it can be
of any dimension. If IM
is logical and the structuring
element is flat, the output image is logical; otherwise the output
image has the same class as the input. If the input is packed binary,
then the output is also packed binary.
gpuarrayIM
must be a gpuArray
of
type uint8
or logical
. When
used with a gpuarray
, the structuring element must
be flat and twodimensional. The output has the same class as the
input.
The binary erosion of A by B, denoted A B, is defined as the set operation A B = {z(B_{z} ⊆ A}. In other words, it is the set of pixel locations z, where the structuring element translated to location z overlaps only with foreground pixels in A.
In the general form of grayscale erosion, the structuring element has a height. The grayscale erosion of A(x, y) by B(x, y) is defined as:
(A B)(x, y) = min {A(x + x′, y + y′) − B(x′, y′)  (x′, y′) ∊ D_{B}},
where D_{B} is the domain
of the structuring element B and A(x,y) is
assumed to be +∞ outside the domain of the image. To create
a structuring element with nonzero height values, use the syntax strel(nhood,height)
,
where height
gives the height values and nhood
corresponds
to the structuring element domain, D_{B}.
Most commonly, grayscale erosion is performed with a flat structuring element (B(x,y) = 0). Grayscale erosion using such a structuring element is equivalent to a localminimum operator:
(A B)(x, y) = min {A(x + x′, y + y′)  (x′, y′) ∊ D_{B}}.
All of the strel
syntaxes except for strel(nhood,height)
, strel('arbitrary',nhood,height)
,
and strel('ball', ...)
produce flat structuring
elements.
For more information on binary erosion, see [1].
[1] Gonzalez, R. C., R. E. Woods, and S. L. Eddins, Digital Image Processing Using MATLAB, Gatesmark Publishing, 2009.
[2] Haralick, Robert M., and Linda G. Shapiro, Computer and Robot Vision, Vol. I, AddisonWesley, 1992, pp. 158205.
[3] van den Boomgard, R, and R. van Balen, "Methods for Fast Morphological Image Transforms Using Bitmapped Images," Computer Vision, Graphics, and Image Processing: Graphical Models and Image Processing, Vol. 54, Number 3, pp. 254258, May 1992.
bwpack
 bwunpack
 conv2
 filter2
 gpuArray
 imclose
 imdilate
 imopen
 offsetstrel
 strel