Edmap Help


This widget lets the user use and modify colormaps. This can control the display of volume data or the display of data mapped to a surface. Volume data brightness is typically controlled from the Brightness sliders in the Edit Volume Widget. A user may sometimes want to use the edmap slider instead (or in addition) to those sliders. By far the most usual reason is to use a custom designed colormap. Once such a map is read in (see Menu Options below) it is modified via this widget. Note: the brightness sliders still get applied to the data, but they are applied first (and they also modify the opacity of the data - brighter voxels being set to higher opacity). After the brightness sliders are applied, the edmap slider is applied (but it only affects color, not opacity).

Use of the Sliders

The edmap widget works similar to the standalone edmap program. The right slider controls which colormap is to be manipulated. The left slider specifies the data value which gets mapped to the first entry in the specified color table (e.g., black if it's a grayscale) and the middle slider specifies the data value which gets mapped to the last entry in the table (e.g., white). Values between are linearly interpolated into the table. Values below the left slider get set to the first entry in the color table. Values above the middle slider get set to the last entry in the table.

Menu Options

This pops up a widget.

Map File

This is the file which contains the colormap. It can also be read in from the command line via the -loadmap option. On an SGI, this colormap is typically created by using /usr/sbin/interp, /usr/sbin/showmap, and /usr/sbin/savemap. When maps are saved via savemap, you should specify a 256 wide range of locations to save. If you save locations 256-511, that is map 1, 512-767 is map 2, etc. On Linux, use my makemap.pl program to create an ascii text file with column 1 the map location (eg, 256-511) and columns 2-4 the red,green, and blue values (0-255). When you load the map into DAVE, it will go to the same map number. Click on "Load" to load the specified colormap.

Volume Map

This specifies which map should be used for the volume data. It should be set to the map number of the map just loaded. Map 15 is the default.

Apply Colormap to Volume Data

When chosen, this causes the colormap in the specified volume map to be applied to the volume data. Otherwise the default internal maps are used alone.

Surface Map

Objects which are read in via pts files can have their surface brightness be set to the value of the data voxel which the surface is passing through (this is done by clicking of the button which toggles from normal mode to data mode on the Edit Object Properties widget; see it for more help). This brightness map is stored in map 1 by default. This entry allows the default to be changed.

NOTE: to change the colormap for Edit->dataplanes specify -Ic 1

(assuming you specify map 1 in loadmap); dataplanes are not

considered volume or surface data. If dataplanes have been displayed

due to -p on the command line, I think -Ic is not necessary.
Copyright 1995 by Lawrence M. Lifshitz and the University of Massachusetts Medical School. All rights reserved.