[Insight-developers] Erosion/Dilation Speed Tests

[Stephen R. Aylward]

Hi,

I ran some speed tests to compare
	itkObject[Erode|Dilate]MophologyImageFilter
with
	itkBinary[Erode|Dilate]ImageFilter

These tests are contained in 
Insight/Testing/Code/BasicFilters/itkObjectMophologyImageFilterTest

Data: 50x50x50, unsigned short image

Windows 2000 - compiled in MSVC++6 with RelWithDebInfo mode.

		Pentium 4		Dual Pentium Xeon
		Avg Time (sec)		Avg Time (sec)
ObjectDilate	0.425			0.14
BinaryDilate	12.37			4.10

ObjectErode	0.035			0.015
BinaryErode	0.130			0.047

So, for Dilation the speedup is ~30x and for erosion the speedup is ~4x. 
   This puts ITK as

Note that ObjectErode is not a 100% compatible implementation of 
erosion.   You actually need to use (radius-1) for the ObjectErosion 
filter to get the same result as with BinaryErosion - I did not do that 
in the above tests - so ObjectErode is actually faster than reported.

What about swapping the names of these two filters?   The 
ObjectDilate/Erode filters assumes there are fixed (user specified) 
foreground and background values.   The BinaryDilate/Erode filters 
perform tests on adjacent pixels to determine what value with which to 
fill a dilation/erosion.

Stephen

-- 
===============================================
Dr. Stephen R. Aylward
Assistant Professor of Radiology
Adjunct Assistant Professor of Computer Science
http://caddlab.rad.unc.edu
aylward@unc.edu
(919) 966-9695