Summary
Pseudocolor images are a single band image with an indexed 'colormap' that matches a specific RGB color to a pixel value. When converting a pseudocolor image to a grid, you must specify a colormap, otherwise the grid will not be created.
Procedure
- Use the DESCRIBE command to determine if the image uses a colormap. The returned Image Type should say: PSEUDOCOLOR.
- Use IMAGEGRID to convert the image to a grid and to create a colormap file. Both output files will be created in the current workspace.
- Process the grid. As long as the grid's values do not change the original, colormap will still be valid.
- If the values of the grid change, you will need to modify the colormap file to reflect any changes. You can use any ASCII text editor to do this.
- Use GRIDIMAGE to convert the grid back to an image. It requires the colormap file to create a pseudocolor image.
![[O-Image] Pseudocolor Image Processing](https://webapps-cdn.esri.com/CDN/support-site/technical-articles-images/000002162/00N39000003LL2C-0EM39000000wcQg.png)
An example:
Arc: describe stcoll_drg.tif
Description of Image stcoll_drg.tif
Image Format : TIFF Image Depth = 8
Image Type : PSEUDOCOLOR Image Bands = 1
Image Colormap : TRUE Number of Columns = 4196
Image Compressed : TRUE Number of Rows = 5518
Image Rotated : FALSE Pixel Size DX = 2.520
Pixel Size DY = 2.520
BOUNDARY STATISTICS
Xmin = 10535.451 No statistic information available
Ymin = 194295.828
Xmax = 21109.696
Ymax = 208201.616
NO COORDINATE SYSTEM DEFINED
Arc: imagegrid
Usage: IMAGEGRID {out_colormap_file} {in_band}
{NEAREST | BILINEAR | CUBIC} {DEFAULT | SQUARE}
Arc: imagegrid stcoll_drg.tif newgrid newgrid.clr
Converting Image to Grid ...
Arc: gridimage
Usage: GRIDIMAGE {NONE | NOMINAL | GRAY | in_colormap_file}
{BIL | BIP | BMP | BSQ | ERDAS | GRASS | IMAGINE | JFIF | RLC | SUNRASTER | TIFF}
{NONE | COMPRESSION | G4 | LZW}
Arc: gridimage newgrid newgrid.clr output.tif tiff
Converting Grid to Image ...
Arc: describe output.tif
Description of Image output.tif
Image Format : TIFF Image Depth = 8
Image Type : PSEUDOCOLOR Image Bands = 1
Image Colormap : TRUE Number of Columns = 4196
Image Compressed : FALSE Number of Rows = 5518
Image Rotated : FALSE Pixel Size DX = 2.520
Pixel Size DY = 2.520
BOUNDARY STATISTICS
Xmin = 10535.451 No statistic information available
Ymin = 194295.828
Xmax = 21109.696
Ymax = 208201.616
NO COORDINATE SYSTEM DEFINED
For more information on the types of images, see the ArcInfo Documentation (ArcDoc) Contents > Cartography > Image Integration > Introducing the Image Integrator > Image types.