Exporting a grid to an image with GRIDIMAGE returns the message:
Output image depth is greater than 8
Output image cannot store colormap
Converting Grid to Image ...
The input grid contains a value larger than 255. Eight-bit images can only store pixel values in the range of 0 to 255.
The warning message indicates the output image will not be 8-bits and that a colormap file will not be created. The output image will be written as a 16-bit greyscale file, which has a range of potential values from 0 to 65535.
If the output image must maintain the grid's colormap, you must modify the grid to fit within a 0 to 255 value range. You can use the SLICE or CON functions to change the value range of the grid.
Using the SLICE functionL
newgrid = SLICE(oldgrid,EQINTERVAL,256,0)
Using the CON function:
newgrid = CON(oldgrid > 255, 255, CON(oldgrid < 0, 0, oldgrid))
You must edit the colormap in an ASCII text editor so the color definitions are associated with the correct areas in the new 0-255 grid.
For a discussion of the colormap file format, see the ArcInfo online Help section Contents > Spatial modeling > Cell-based Modeling with GRID > Displaying grids > Assigning colors for grid display > Creating a colormap file.