5th Intensive Course on Soil Micromorphology
Naples 2001
12th - 14th September
Image Analysis
Lecture 9
Grey-Level Morphology and Multi-Spectral
Methods
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Multi-Spectral Methods for Segmentation/Classification
useful where X-ray spectra of different colour information (e.g. RED/GREEN/BLUE/ U-V) information is available
Part 1
Part 2
Extension of Binary Morphology to Grey-Level Images
avoids need to segment images
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
•Segmentation (usually by thresholding) and attendant problems
•Erosion involves stripping pixels from edge of foreground areas according to selected criteria
•Dilation involves adding pixels to foreground areas
•Opening involves one cycle of erosion followed by one cycle or dilation
roughness aspects of feature are not recovered, no are particles smaller than 2 pixels
•Closing is the reverse of Opening.
Binary Morphology requires
Grey Level Morphology
• attempts to solve problems of BINARY MORPHOLOGY
by removing need for thresholding
• Grey Level Erosion replaces all intensities within a given
mask area by the minimum value in that area
• Grey Level Dilation replaces all intensities within a given
mask area by the maximum value in that area
• A grey level opening involves an erosion and a dilation phase
As with binary morphology, roughness is lost and features tend to become rounded until they finally disappear
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Representation of binary morphology for feature sizing
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Schematic of Intensity Profile along a line
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Start of Erosion along line
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Intensity lost after grey-level erosion (blue)
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Intensity lost after grey-level erosion followed by dilation
Blue: Intensity lost: Green: Intensity recovered in dilation
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Intensity lost after grey-level erosion of diameter 5
Cyan: New Intensity lost
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Intensity lost after grey-level erosion followed by dilation(diameter 5)
Blue/ Cyan: Intensity lost: Green: Intensity recovered in dilation
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Intensity lost after grey-level erosion of diameter 7
Purple: New Intensity lost
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Intensity lost after grey-level erosion followed by dilation(diameter 7)
Blue/ Cyan/Purple: Intensity lost: Green: Intensity recovered in dilation
Effect of grey-levelopening at different radii
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
a) Radius 9 pixels
b) Radius 10 pixels
c) Difference Image
d) Complete particle loss
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Particle size analysis using grey-level morphology
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5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Core sample taken from estuary model.
[photograph courtesy of J.Alexander]
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Halimeda needles from Great Barrier Reef
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Halimeda needles from Great Barrier Reef
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Halimeda needles from Great Barrier Reef - partly covered by nanograins
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Halimeda needles from Great Barrier Reef - partly covered by nanograins
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Halimeda needles from Great Barrier Reef - fully covered by nanograins
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
Question: Are nanograins biological or chemical in origin?
Evidence suggests nanograins increase in size with coverage - hence favouring chemical argument.
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Grey-Level Morphology
If particles lost at each radius are stored and finally added (B) - the resulting image should be comparable to original (A).
Except: All particles are reduced to their equivalent circular
diameter.
•Allows alternative methods for segmentation
•Enables separation of different mineral classes.
•Can be used in combination with Orientation Analysis as a combination method to overcome problem of large particles
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Analysis
Requirements:
Two or more images of same area at same magnification and pixel resolution and in exact registry.
Must be collected with different physical parameters - e.g. wavelength
Multi-Spectral Analysis
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Analysis
Examples:
Optical Microscopy:
•Red / Green / Blue images
•UV.
Electron Microscopy:
•Secondary Electron
•Back Scattered Electron
•Cathodoluminescence
•X-Ray Maps.
Requirements continued:
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Require 2 or more different images of same area
must be in exact registry
e.g. Optical Microscope
RED/GREEN/BLUE/UV
Or SE / BSE Image and CL or various X - Ray Maps in SEM
Multi-Spectral Methods
Hong Kong Marine Clay from M1 unit approximately 1m above upper most palaeo-desiccated layer. BSE Image
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Hong Kong Marine Clay
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
BSE Image X-Ray Maps
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
From N images
and
Statistics from M classes
Output segmented image may be obtained.
Accuracy in segmentation relies on identification of suitable classes, and also sufficient classes
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Are these two particles the same material?Classification was set at 98% confidence and some post-processing was done to produce classified image.
Procedure of segmentation is know as Mineral-Segmentation
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
large voids 2.21% matrix 73.49% matrix in aggregate 14.46% quartz 5.27% feldspar 2.70% chalk 0.64% rutile 0.15% magnetite 0.65% pyrite 0.43%
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Particle Size Distribution for different mineral species
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Binary Mask to assess orientation in matrix outside aggregate. Large mineral grains and voids are black as is aggregate.
Binary Mask to assess orientation in matrix inside aggregate.
Use Mineral Segmented image to generate binary masks.
Domain Segmentation of Matrix
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Hong Kong Marine Clay
a) Matrix orientation c) Quartz grain orientation e) Weighted Quartz grain orientation
b) Aggregate orientation
d) Feldspar orientation f) Weighted Feldspar orientation
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
Index of Anisotropy
outside aggregate: 0.229
inside aggregate: 0.374
In both cases the predominant orientation is nearly vertical.
Vertical direction in field.
5th Intensive Course on Soil Micromorphology - Naples 2001Image Analysis - Lecture 9: Multi-Spectral Methods
When does a particle warrant separate identification from matrix?
- depends on pixel resolution/magnification.
In supervised classification it is helpful to avoid “forced” classification as this will identify features / minerals which may have been missed.
Some post-processing of image in needed following Mineral-Segmentation to remove noise etc.
Concluding Remark on Multi-spectral Analysis.