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Re: Mac 32 bit color depth?


Yes, I can confirm this behavior on a Mac G4 running system 9.04:

!P.Color = 256L^(depth /8) - 1
!p.color =           -1
!P.Color = 256L^((depth < 24) /8) - 1
!p.color =     16777215
** Structure !VERSION, 7 tags, length=44:
   ARCH            STRING    'PowerMac'
   OS              STRING    'MacOS'
   OS_FAMILY       STRING    'MacOS'
   RELEASE         STRING    '5.4'
   BUILD_DATE      STRING    'Nov  1 2000'
   MEMORY_BITS     INT             32
                   INT       =       32

I don't understand the meaning of 32bit displays. It is possible to have
32 bit depths on Windows platforms also.  I don't have a Windows machine
handy with IDL5.4, but it would be nice to see the results of the above
on those machines.

It maybe unrelated to what your asking, but note that David posted the
following recently (see Pavel's post on 'Open file in 5.4'):

> What I have noticed is that on a 32-bit display, it
> seems almost impossible to flip back and forth between
> Device, Decomposed=0 and Device, Decomposed=1. What is
> the best way to be able to display either a 24-bit or
> an 8-bit image? It seems to me the color table vectors
> have to be re-loaded every time you set Decomposed=0.
> Is this what you recommend?


Wayne Landsman wrote:
> I have a simple program that tries to reset the default value of
> !P.COLOR for the current (Mac, Win or X) device using the following
> code:
> device, get_visual_depth=depth
> !P.Color = 256L^(depth/8) - 1
> I am told that this fails on IDL V5.4 on a Mac since
> device,/get_visual_depth returns a value of 32 (whereas !P.COLOR is
> 256L^24 -1).   Can other Mac users verify this?      What is the meaning
> of a 32 bit  visual depth?
> Thanks,  --Wayne
> Wayne
> Landsman
> landsman@mpb.gsfc.nasa.gov

Ben Tupper
Bigelow Laboratory for Ocean Sciences
180 McKown Point Rd.
W. Boothbay Harbor, ME 04575