Dialog Based Initialization (Delphi 4.0)

The Color Conversion API provides a color space dialog that can be used to initialize a conversion. To do a dialog based initialization follow the steps below:

function TForm1.ColorDlg_RGBToLAB({in}pSrcRGB, {out}pDstLAB: Pointer; {in}nWidth, {out}nHeight: Integer) : {ret}Integer;
var
    ClrHandle : THandle; (* color handle *)
    ret: Integer; (* return value *)
begin
    (*
     ******************************************************************
     * Simple conversion from RGB to CIELab using the LEAD color dialog *
     * 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 an error code otherwise *
     ******************************************************************
     *)
   
    (*
     * when the dialog appears choose RGB to LAB conversion from
     * the Miscellaneous options
     *)
    ret := L_ClrDlg(DLG_LAB, (* CIELAb color dialog *)
       Handle, (* Handle to parent window *)
       @ClrHandle, (* I need a color handle *)
       nil (* no need for a CONVERSION_PARAMS data *)
       );
   
    (* 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;