EE 4780

1
EE 4780

• Matlab tutorial

2
MATLAB

• Review your matrix-vector knowledge
• Matlab help files are helpful to learn it
• Exercise
• f 1 2 3 4
• g 1 1
• g 1 1
• g
• z f g
• n010
• plot(sin(n))
• plot(n,sin(n)) title(Sinusoid) xlabel(n)
  ylabel(Sin(n))
• n00.110
• plot(n,sin(n))
• grid
• figure subplot(2,1,1) plot(n,sin(n))
  subplot(2,1,2) plot(n,cos(n))

3
MATLAB

• Some more built-ins
• a zeros(3,2)
• b ones(2,4)
• c rand(3,3) Uniform distribution
• help rand
• help randn Normal distribution
• d1 inv(c)
• d2 inv(rand(3,3))
• d3 d1d2
• d4 d1-d2
• d5 d1d2
• d6 d1.d3
• e d6()

4
MATLAB

• Image processing in Matlab
• ximread(cameraman.tif)
• figure
• imshow(x)
• h,wsize(x)
• yx(0h/2,0w/2)
• imwrite(y,man.tif)
• To look for a keyword
• lookfor resize

5
MATLAB

• M-file
• Save the following as myresize1.m
• function ymyresize1(x)
• This function downsamples an image by two
• h,wsize(x)
• for i1h/2,
• for j1w/2,
• y(i,j) x(2i,2j)
• end
• end
• Compare with myresize2.m
• function ymyresize2(x)
• This function downsamples an image by two
• h,wsize(x)
• for i0h/2-1,
• for j0w/2-1,
• y(i1,j1) x(2i1,2j1)
• end
• end

• Compare with myresize3.m
• function ymyresize3(x)
• This function downsamples an image by two
• y x(12end,12end)
• We can add inputs/outputs
• function y,height,widthmyresize4(x,factor)
• Inputs
• x is the input image
• factor is the downsampling factor
• Outputs
• y is the output image
• height and width are the size of the output
  image
• y x(1factorend,1factorend)
• height,width size(y)