Depending upon the graphics hardware on your system you can work in
PseudoColor mode (8 bits per pixel) or RGB mode (24 bits per pixel).
In both modes the values of image pixels are scaled to an integer number
in the range [0,255].
That number then serves as an index into a Color Lookup Table (LUT) which determines the actual color of that pixel.
In PseudoColor mode that index is the same for the red, green and blue color,
whereas in RGB mode we use three image pixels per screen pixel and they serve
as independent indices for the three colors. These three image pixels maybe in
different planes of the same 3-dim image or in different 2-dim images.
Accordingly, we use three image memories (channel 0, 1 and 2) for the red,
green and blue component of an image.
You set MIDAS to PseudoColor or RGB mode via the command
INITIALIZE/DISPLAY (by default PseudoColor mode is set up).
Assuming you have a 3-dim image realima.bdf with the red part in the 1st
plane, green part in the 2nd and blue part in the 3rd plane, you can either
load each plane individually into the corresponding image channel:
INITIALIZE/DISPLAY p5=RGBor do it in one go:
LOAD/IMAGE realima,1 0
LOAD/IMAGE realima,2 1
LOAD/IMAGE realima,3 2 !note that channels begin with 0
INITIALIZE/DISPLAY p5=RGBThe red plane is stored in channel 0, the green plane in channel 1 and the blue plane in channel 2. All three planes are combined for the display of the image.
LOAD/IMAGE realima,1,3 0,...
With the command RESET/DISPLAY we delete all existing display (and
graphics) windows and get back into initial mode, which is PseudoColor.
You can only work within one Color mode at the same time. However, if the
hardware supports it, you can run two parallel Midas sessions with one using
PseudoColor mode and the other one RGB mode.
Image displays are created on the screen via the
CREATE/DISPLAY command. An ``image display'' is then represented by
a window on the bitmapped screen, also called ``display window'' in the
following. It may contain one or several image
channels (max. 12 currently) in PseudoColor, whereas you always have 3 channels
in RGB mode.
An overlay channel for graphics and text and an alpha memory are
associated with an image display.
The image channels may have the same size as the display window or
could be larger.
These channels are not realised
in hardware (e.g. video memory) like for a peripheral image display, but
exist as data structures in main memory.
Images may be displayed (loaded in MIDAS terminology) in image channels
and it is also possible to draw graphs and write text into these channels.
For the (single) overlay channel only drawing and writing of text is supported
which will then be shown on top of the currently active image channel.
The alpha memory is used to display information about the displayed image.
Initially each display is provided with a grayscale LUT.
You may create several image displays at the same time on your bitmapped
screen even though only one display can be the current active display window at
any time. With the command ASSIGN/DISPLAY you switch from one
display to the next.
Each image channel of a display window has independent scroll and
zoom (emulated in software).
You can also connect a zoom window to a display window. This window can
then be used by commands such as GET/CURSOR
and VIEW/IMAGE to provide a zoomed view of the subframe pointed at with
the mouse.
The display windows can be moved and resized. After resizing you have to reload
the previously loaded (displayed) image again.
Up to 9 different display windows of differing size can be created in a
MIDAS session at a given moment.
By running several MIDAS sessions in parallel you can create
an unlimited amount of display windows which share the same LUT or
not, depending upon the capabilities of your X-display system.
You can also create display windows on other X-displays within a MIDAS
session. A special kind of display windows, so-called shadow displays
can be connected to any display window created before.
Then, all activity on that display
window is replayed on the shadowing window (which could be on an X-display
in another room).
The most important commands associated with display windows
are:
INITIALIZE/DISPLAY - setup Color mode, size of LUTs, etc.
CREATE/DISPLAY - create an image display with image channels(s)
ASSIGN/DISPLAY - switch between different display windows
DELETE/DISPLAY - delete a display window
SHOW/DISPLAY - show status of active display
MODIFY/DISPLAY - change display window from full view to icon status
RESET/DISPLAY - delete all windows and get back into inital state