Built-in Conversion (Delphi 4.0)

The Color Conversion C API provides built-in conversion. To do a built-in conversion, follow the steps below:

1. At the beginning of the Unit1 file, add LTDLLUNT, LTDLLTYP, and LTDLLDEF to the uses section.

2. Use the following code to perform the built-in conversion:
   

   function TForm1.Builtin_RGBToLAB({in}pSrcRGB, {out}pDstLAB: Pointer; {in}nWidth, {in}nHeight: Integer) : {ret}Integer; 
   var 
   ClrHandle : THandle;           (* color handle           *) 
   params    : CONVERSION_PARAMS; (* conversion params      *) 
   WPoint    : WHITEPOINT ;       (* white point definition *) 
   ret       : Integer;           (* return value           *) 
   begin 
   (* 
   ****************************************************************** 
   * Simple conversion from RGB to CIELab using built-in conversion * 
   * Parameters :                                                   * 
   * pSrcRGB : 24 bit RGB data, this is the input image data        * 
   * pDstLAB : 24 bit CIELab data, this is the output image data    * 
   * nWidth  : Width of the image                                   * 
   * nHeight : Height of the image                                  * 
   * Returns SUCCESS when successful or error code else             * 
   ****************************************************************** 
   *) 
   (* initialize the conversion structure *) 
   ZeroMemory(Pointer(@params), SizeOf(CONVERSION_PARAMS)); 
   (* set the whitepoint *) 
   params.pWpoint := @WPoint; 
   (* set up default conversion data *) 
   params.uStructSize  := sizeof(CONVERSION_PARAMS); 
   params.pWpoint.nWhitePoint     := CIELAB_D50; 
   params.nQuantization  := 8; 
   params.nMethod  := USE_BUILTIN; 
   params.nActiveMethod  := USE_BUILTIN; 
   params.pWpoint.xWhite  := 0.0; 
   params.pWpoint.yWhite  := 0.0; 
   (* initialize the conversion engine *) 
   ret := L_ClrInit(@ClrHandle, 
   CCS_RGB, 
   CCS_LAB, 
   @params); 
   (* do we have a valid handle *) 
   if ret <> SUCCESS then 
      Result := ret 
   else 
      begin 
   (* do the conversion from RGB to CIELab *) 
   ret := L_ClrConvert (ClrHandle, 
   pSrcRGB, 
   pDstLAB, 
   nWidth, 
   nHeight, 
   0, 
   0); 
   if ret <> SUCCESS then 
      begin 
   (* free before leaving *) 
   L_ClrFree (ClrHandle); 
   Result := ret; 
   end 
   else 
      begin 
   (* do not forget to free every thing *) 
   ret := L_ClrFree (ClrHandle); 
   Result := ret; 
   end; 
   end; 
   end;