How to load color table in a indexed mode file??

Question

How to load color table in a indexed mode file??
Actually, if i opened a indexed file and want to edit color table by loading another color table from desktop (or any other location), any way to do this through java scripting??

Answer 1

continuing...
I wrote a script to read a color table from a GIF file and save to an ACT color table file. I think it might be useful for someone.
It goes a little more deeper than the code I posted before, as it now identifies the table size. It is important because it tells how much data to read.
Some gif files, even if they are saved with a reduced palette (less than 256), they have all the bytes for the full color palette filled inside the file (sometimes with 0x000000). But, some gif files exported in PS via "save for web" for example, have the color table reduced to optimize file size.
The script store all colors into an array, allowing some kind of sorting, or processing at will.
It uses the xlib/Stream.js in xtools from Xbytor
Here is the code:
// reads the color table from a GIF image
// saves to an ACT color table file format
#include "xtools/xlib/Stream.js"
// read the 0xA byte in hex format from the gif file
// this byte has the color table size info at it's 3 last bits
Stream.readByteHex = function(s) {
  function hexDigit(d) {
    if (d < 10) return d.toString();
    d -= 10;
    return String.fromCharCode('A'.charCodeAt(0) + d);
  var str = '';
  s = s.toString();
     var ch = s.charCodeAt(0xA);
    str += hexDigit(ch >> 4) + hexDigit(ch & 0xF);
  return str;
// hex to bin conversion
Math.base = function(n, to, from) {
     return parseInt(n, from || 10).toString(to);
//load test image
var img = Stream.readFromFile("~/file.gif");
hex = Stream.readByteHex(img);      // hex string of the 0xA byte
bin = Math.base(hex,2,16);          // binary string of the 0xA byte
tableSize = bin.slice(5,8)          // Get the 3 bit info that defines size of the ct
switch(tableSize)
case '000': // 6 bytes table
  tablSize = 2
  break;
case '001': // 12 bytes table
  tablSize = 4
  break;
case '010': // 24 bytes table
  tablSize = 8
  break;
case '011': // 48 bytes table
  tablSize = 16
  break;
case '100': // 96 bytes table
  tablSize = 32
  break;
case '101': // 192 bytes table
  tablSize = 64
  break;
case '110': // 384 bytes table
  tablSize = 128
  break;
case '111': // 768 bytes table
  tablSize = 256
  break;
//========================================================
// read a color (triplet) from the color lookup table
// of a GIF image file | return 3 Bytes Hex String
Stream.getTbColor = function(s, color) {
  function hexDigit(d) {
    if (d < 10) return d.toString();
    d -= 10;
    return String.fromCharCode('A'.charCodeAt(0) + d);
  var tbStart = 0xD; // Start of the color table byte location
  var colStrSz = 3; // Constant -> RGB
  var str = '';
  s = s.toString();
     for (var i = tbStart+(colStrSz*color); i < tbStart+(colStrSz*color)+colStrSz; i++) {
          var ch = s.charCodeAt(i);
          str += hexDigit(ch >> 4) + hexDigit(ch & 0xF);
      return str;
var colorHex = [];
importColors = function (){
     for (i=0; i< tablSize; i++){ // number of colors
          colorHex[i] = Stream.getTbColor(img, i);
importColors();
// remove redundant colors
// important to determine exact color number
function unique(arrayName){
     var newArray=new Array();
     label:for(var i=0; i<arrayName.length;i++ ){ 
          for(var j=0; j<newArray.length;j++ ){
               if(newArray[j]==arrayName[i])
                    continue label;
          newArray[newArray.length] = arrayName[i];
     return newArray;
colorHex = unique(colorHex);
// we have now an array with all colors from the table in hex format
// it can be sorted if you want to have some ordering to the exported file
// in case, add code here.
var colorStr = colorHex.join('');
//=================================================================
// Output to ACT => color triplets in hex format until 256 (Adr. dec 767)
// if palette has less than 256 colors, is necessary to add the
// number of colors info in decimal format to the the byte 768.
ColorNum = colorStr.length/6;
lstclr = colorStr.slice(-6); // get last color
if (ColorNum < 10){
ColorNum = '0'+ ColorNum;
cConv = function (s){
     var opt = '';
     var str = '';
     for (i=0; i < s.length ; i++){
          for (j=0; j<2 ; j++){
               var ch = s.charAt(i+j);
               str += ch;
               i ++;
          opt += String.fromCharCode(parseInt(str,16));
          str = '';
     return opt
output = cConv(colorStr);
// add ending file info for tables with less than 256 colors
if (ColorNum < 256){
     emptyColors = ((768-(colorStr.length/2))/3);
     lstclr = cConv(lstclr);
     for (i=0; i < emptyColors ; i++){
          output += lstclr; // fill 256 colors
output += String.fromCharCode(ColorNum) +'\xFF\xFF'; // add ending bytes
Stream.writeToFile("~/file.act", output);
PeterGun