Indesign script colorTransform methode incorrect return value

Hi @árpádp3188668 

By one of those obscure whims that belong only to the Adobe dev team, the method app.colorTransform(…) expects and returns numbers in 0…1 — except for the LAB color space which still uses the original colorValue ranges (L: 0…100, a: -100..100, b: -100..100). So you need to properly downscale (then upscale) the values found in your Swatch/Color objects, as dictated by the specific color spaces under consideration.

Best is to have in your toolbox an adapter routine, like this:

function colorTransform(/*num[]*/vals,/*str|ColorSpace*/from,/*str|ColorSpace*/to,/*int=0*/dec,  a,k,i)
//----------------------------------
// vals :: array of numbers *as processed by Color.colorValue*, that is
//       - [0..255, 0..255, 0..255]         in RGB space
//       - [0..100, 0..100, 0..100, 0..100] in CMYK space
//       - [0..100, -128..127, -128..127]   in LAB space
//       - [0..360, 0..100, 0..100]         in HSB space
// (Rem: MixedInk is not supported by app.colorTransform.)
// from  :: source ColorSpace or key string ('RGB'|'CMYK'|'HSB'|'LAB')
// to    :: dest. ColorSpace or key string ('RGB'|'CMYK'|'HSB'|'LAB')
// dec   :: rounding decimal digits (use -1 to bypass rounding);
//          default is 0, i.e. rounding to the nearest integer.
// Returns the converted values as a new array of 3 or 4 numbers in
// the expected ranges (i.e. as processed by Color.colorValue).
// => num[]
{
   from = from.toString().toUpperCase();
   to = to.toString().toUpperCase();
   
   if( from==to ) return vals.slice();

   switch( from )
   {
      case 'RGB':
         // app.colorTransform() expects r,g,b values in 0..1 (!)
         // -> divide by 255
         a = [ vals[0]/255, vals[1]/255, vals[2]/255 ];
         break;

      case 'CMYK':
         // app.colorTransform() expects c,m,y,k values in 0..1 (!)
         // -> divide by 100
         a = [ .01*vals[0], .01*vals[1], .01*vals[2], .01*vals[3] ];
         break;

      case 'HSB':
         // app.colorTransform() expects h,s,b values in 0..1 (!)
         // -> divide h by 360 and s,b by 100
         a = [ vals[0]/360, .01*vals[1], .01*vals[2] ];
         break;

      case 'LAB':
         // app.colorTransform() expects L,a,b values as given in original range,
         // that is, L:0..100, a:-100..100, b:-100..100
         a = vals.slice();
         break;

      default:
         throw "Unsupported color space " + from;
   }

   try
   {
      a = app.colorTransform(a, ColorSpace[from], ColorSpace[to]);
   }
   catch(e)
   {
      throw "Unable to convert " + a + " from " + from + " to " + to + " [" + e + "]";
   }

   switch( to )
   {
      case 'RGB':
         // app.colorTransform() returns r,g,b values in 0..1 (!)
         // -> multiply by 255
         a[0]*=255; a[1]*=255; a[2]*=255;
         break;

      case 'CMYK':
         // app.colorTransform() returns c,m,y,k values in 0..1 (!)
         // -> multiply by 100
         a[0]*=100; a[1]*=100; a[2]*=100; a[3]*=100;
         break;

      case 'HSB':
         // app.colorTransform() returns h,s,b values in 0..1 (!)
         // -> multiply h by 360 and s,b by 100
         a[0]*=360; a[1]*=100; a[2]*=100;
         break;
      
      case 'LAB':
         // app.colorTransform() returns L,a,b values in original range,
         // that is, L:0..100, a:-100..100, b:-100..100

      default:;
   }
   
   
   if( 0 <= (dec|=0) )
   {
      k = Math.pow(10,dec);
      for(i=a.length ; i-- ; a[i]=Math.round(k*a[i])/k );
   }
   
   return a;
}

// TEST: Transform the CMYK color [41,46,56,36] to RGB
// ---
var res = colorTransform( [41,46,56,36], 'CMYK', 'RGB' );
alert( res ); // => 113,97,82

Best,

Marc