(x^(3))^(1/3) doesn't simplify to x.  I am missing something.

For example - I have a for loop acting on a Matrix

a:=Matrix(20,20,rand(0..1.)

for i from 1 to 20 do
  for j from 1 to 20 do
    if a[i,j]<0.2 then a[i,j]:=0 end if:
  end do:
end do:

Is there an equivalent sequence loop?  I tried to set up a double seq to set the values in the matrix but this fails

seq(seq(`if`(a[i,j]<0.2,a[i,j]:=0,a[i,j]),i=1..20),j=1..20)

Is it possible to read in specific parts of a bmp image? 

Stupid question, but how do I get the code on the math apps CaesarCipher from the help page?  I see the variable cipher but it's content is a mystery.

(Sorry guys, I changed the title to better reflect the content of the question and it bumped back up the top)

Used to know, I think.  How do you convert a Matrix to an image?  I want to use the PadImage command from the ImageTools package.