imshow help

[Mike Zabrocki]

Hi,
    I am trying to learn some basics of Octave with imshow() and I
seem to have found places where the documentation does not agree
with the behavior of the program.

First, on the reference card it says that there is an
imshow(r,g,b)
As far as I can tell this option does not exist and is
not consistent with the documentation in the regular
documentation which seems to say that the command is
"imshow (rgb, . . . )
...
Display the image im, where im can be a 2-dimensional (gray-scale  
image) or a 3-
dimensional (RGB image) matrix."

Since I wasn't able to get the imshow(r,g,b) function to
work can I assume that it is not right?


Next, I cannot tell what are the minimum and maximum values
of the RGB values.  It says in the documentation that
"The actual meaning of the value of a pixel in a gray-scale or RGB  
image depends on the
class of the matrix. If the matrix is of class double pixel  
intensities are between 0 and 1, if
it is of class uint8 intensities are between 0 and 255, and if it is  
of class uint16 intensities
are between 0 and 65535."

So I try to make a simple grey image.
x(:,:,1) = uint8(ones(100)*100);
x(:,:,2) = uint8(ones(100)*100);
x(:,:,3) = uint8(ones(100)*100);
imshow(x)
and the image is completely white.  What happened to the 0 to 255 range?
I have found other reports of odd behavior with imshow on the
forum

Next I need some help getting an image into Octave format.
Given that Octave only reads one format I need to put my
images in that.  Does anyone have any documentation or examples
how this is done?

Thanks,
-Mike Zabrocki

P.S. I'm using Octave 3.0.1 on a Mac PPC