An Overview of the MATLAB Image Processing Toolbox

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An Overview of the MATLAB Image Processing Toolbox

• Hanif M. Ladak, Ph.D.

Medical Biophysics and Electrical Computer
Engineering, UWO Imaging Research Labs, The John
P. Robarts Research Institute
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MATLAB
Numeric computation visualization software.
Main MATLAB program
...
Image processing
Statistics
Controls
Optional toolboxes
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COMMAND PROMPT
Define variables and call functions at command
prompt. E.g. gtgt x 1 DEMO
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GETTING HELP

• http//www.mathworks.com/access/helpdesk/help/help
  desk.shtml
• MATLAB link
• Image Processing Toolbox link
• gtgt help topic

Discuss and demonstrate MATLAB 5.3, version 2.2.1
of image processing toolbox. Latest version is
MATLAB 6.5, version 3.2 of toolbox.
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OVERVIEW

• gtgt help images
• Image I/O
• Image display
• Pixel values and statistics
• Geometric operations
• Image enhancement and analysis
• Linear filtering and design
• Transforms
• Region-of-interest (ROI) operation
• Binary image operations
• Neighborhood block operations

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IMAGE I/O

• gtgt im imread(pout.tif)
• JPEG
• TIFF
• HDF
• PCX
• XWD
• imwrite, imfinfo

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INTENSITY IMAGES
100 7 125 17 233 233 1 77 120 112 60 65 123 33
244...

• Data types
• uint8 uint16
• double

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IMAGE DISPLAY

• gtgt imshow(im)
• gtgt colorbar
• gtgt help imshow

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GEOMETRIC OPERATIONS

• Interpolation (interp2)
• Resizing (imresize)
• Cropping (imcrop)
• Rotation (imrotate)

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GEOMETRIC OPERATIONS
gtgt imcrop
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PIXEL VALUES STATS

• Inspect pixel values (pixval)
• Values along path (improfile)
• Histogram (imhist)
• mean2, std, corr2

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PIXEL VALUES STATS
gtgt imhist(im)
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IMAGE ENHANCEMENT

• Adjust intensity
• imadjust
• histeq
• Noise removal
• linear filtering
• median filtering
• adaptive filtering

gtgtim2 histeq(im) gtgtimshow(im2)
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IMAGE ENHANCEMENT

• Adjust intensity
• imadjust
• histeq
• Noise removal
• linear filtering
• median filtering
• adaptive filtering

gtgtim2 medfilt2(im, 3 3)
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IMAGE ANALYSIS

• Edge detection
• Sobel
• Prewitt
• LoG
• Roberts
• Canny
• Quadtree decomposition

gtgtbw edge(im, canny, 0.25, 1.0)
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REGION-BASED OPERATIONS

• Specify a region (roipoly)
• Filter a region (roifilt2)
• Fill a region (roifill)

gtgtmask roipoly
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REGION-BASED OPERATIONS
gtgth fspecial(unsharp) gtgtim2 roifilt2(h,
im, mask)
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LINEAR FILTERING

• Convolution
• conv2
• Predefined filters
• fspecial, filter2
• Filter design

gtgt h fspecial( average, 5 ) gtgt im2
uint8( round( filter2(h, im) ) )
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TRANSFORMS

• 1. Fourier Transform
• -fft2, fftshift, ifft2
• 2. Discrete Cosine Transform (DCT)
• -dct2, idct2, dctmtx, dctdemo
• 3. Radon Transform
• -radon, iradon, phantom
• 4. Wavelet Transform

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TRANSFORMS
gtgt I fft2(im) gtgt I2 fftshift2(I) gtgt
imshow(log(abs(I2)), notruesize) gtgt
colormap(jet) gtgt colorbar
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NEW FEATURES (3.2 vs. 2.2.1)

• Landmark-based image registration
• interactive landmark selection
• specification of transformation and computation
  of transformation parameters
• Deblurring
• Wiener, Regularized, Lucy-Richardson
• Iterative blind deconvolution
• Expanded set of morphological operators

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CONCLUSION
Just do it! -Nike