[mmhistogram] [Up] [mmblob] Measurements

mmlabel
Label a binary image.

Synopsis

y = mmlabel( f, Bc = None )

Implemented in Python.

Input

f Image Binary image.

Structuring Element

( connectivity).

Default: None (3x3 elementary cross)

Output

y	Image If number of labels is less than 65535, the data type is uint16, otherwise it is int32.

Description

mmlabel creates the image y by labeling the connect components of a binary image f, according to the connectivity defined by the structuring element Bc. The background pixels (with value 0) are not labeled. The maximum label value in the output image gives the number of its connected components.

Examples

Numerical Example

>>> f=mmbinary([
   [0,1,0,1,1],
   [1,0,0,1,0]])

>>> g=mmlabel(f)

>>> print g

[[0 1 0 2 2]
 [3 0 0 2 0]]

Image Example

The maximum label value gives the number of connected blobs in the image.

>>> f = mmreadgray('blob3.tif')

>>> g=mmlabel(f)

>>> nblobs=mmstats(g,'max')

>>> print nblobs

18.0

>>> mmshow(f)

>>> mmlblshow(g)


f	g

Equation

Where H is the number of image rows, and y1 and y2 are the row and column coordinates respectively.

Source Code
        def mmlabel(f, Bc=None):
    from Numeric import allclose, ravel, nonzero, array
    if Bc is None: Bc = mmsecross()
    assert mmisbinary,'Can only label binary image'
    zero = mmsubm(f,f)               # zero image
    faux=f
    r = array(zero)
    label = 1
    y = mmgray( f,'uint16',0)        # zero image (output)
    while not allclose(faux,0):
        x=nonzero(ravel(faux))[0]      # get first unlabeled pixel
        fmark = array(zero)
        fmark.flat[x] = 1              # get the first unlabeled pixel
        r = mminfrec( fmark, faux, Bc) # detects all pixels connected to it
        faux = mmsubm( faux, r)        # remove them from faux
        r = mmgray( r,'uint16',label)  # label them with the value label
        y = mmunion( y, r)             # merge them with the labeled image
        label = label + 1
    return y
    
      

mmlabelflat	Label the flat zones of gray-scale images.
mmfreedom	Control automatic data type conversion.
mmsebox	Create a box structuring element.
mmsecross	Diamond structuring element and elementary 3x3 cross.
mmareaopen	Area opening
mmblob	Blob measurements from a labeled image.
mmgrain	Gray-scale statistics for each labeled region.

[`mmhistogram`] [Up] [`mmblob`]
Copyright (c) 2003, Roberto A. Lotufo, UNICAMP-University of Campinas; Rubens C. Machado, CenPRA-Renato Archer Research Center.

mmlabel Label a binary image.