Columnwise neighborhood operations
processes the image B
= colfilt(A
,[m n]
,block_type
,fun
)A
by rearranging each
m
byn
block of A
into a column of a temporary matrix, and then applying the function
fun
to this matrix. colfilt
zeropads
A
, if necessary.
subdivides B
= colfilt(A
,[m n]
,[mblock nblock]
,block_type
,fun
)A
into regions of size
mblock
bynblock
blocks to save memory.
Note that the result of the operation does not change when using the
[mblock nblock]
argument.
For example, if [mblock nblock]
is [3 4]
and the size of each block is 16by16 pixels, then colfilt
subdivides the image into regions of size 48by64 pixels and processes each region
separately.
The algorithm that colfilt
uses to process images depends on the
value of block_type
.
Value 
Description 





To save memory, the colfilt
function might divide
A
into subimages and process one subimage at a time. This
implies that fun
may be called multiple times, and that the first
argument to fun
may have a different number of columns each
time.