Emulation Tables

The LEAD Color Conversion toolkit provides emulation tables as one of its conversion methods. This method however is provided only for the following conversions:

CMYK to RGB.
CIELab to RGB
and RGB to CIELab

The Emulation tables' method supports both built-in and custom options. For built-in emulation tables, use the USE_ET option. The custom emulation tables' option, USE_CUSTOM_ET, provides custom conversion using user-supplied images, converted from the source images distributed with the library, by any tool, as follows:

Conversion	Source	Convert to
CMYK to RGB	src_cmyk_image.tif	RGB image (i.e. dst_cmyk2rgb_image.tif)
RGB to Lab	src_rgb_image.tif	Lab image (i.e. dst_rgb2lab_image.tif)
Lab to RGB	src_lab_image.tif	RGB image (i.e. dst_lab2rgb_image.tif)

A set of images, already converted and ready for use (dst_cmyk2rgb_image.tif, dst_rgb2lab_image.tif, and dst_lab2rgb_image.tif), is provided. However, using the provided set of converted images will produce the same results as the built-in emulation tables.

The code below shows how a conversion can be done using the built-in tables:

L_VOID Tables_Convert_CMYKToRGB(L_UCHAR *pInput, L_UCHAR *pOutput, L_INT nWidth)
{
   HANDLE ClrHandle /*Color Handle*/;
   CONVERSION_PARAMS params  /*Conversion options*/;

   /* Zero initialize, this step is important*/
   ZeroMemory (&params, sizeof (CONVERSION_PARAMS));

   /*Conversion with options.
     The conversion will be done with the options specified in the
     params variable
   */

   /* Set the params size */
   params.uStructSize = sizeof (CONVERSION_PARAMS);

   /* We want to use built-in emulation tables */
   params.nMethod = USE_ET;

   /* set the active conversion method */
   params.nActiveMethod = USE_ET;

   /* initialize the color conversion */
   L_ClrInit (&ClrHandle, /*pointer to color handle to be returned*/
             CCS_CMYK, /*input color space*/
             CCS_RGB, /*output color space*/
             &params /*pointer to the initialization options*/
            );

   /* Convert the image buffer */
   L_ClrConvert (ClrHandle, /* conversion handle*/
                 pInput, /* input buffer*/
                 pOutput, /* output buffer*/
                 nWidth, /*pixel's width*/
                 nHeight, /*pixel's height*/
                 0, /* 0 bytes align*/
                 0); /*0 bytes align*/

   /* free the conversion */
   L_ClrFree (ClrHandle);
}

The code below shows how a conversion can be done using user-defined tables:

L_VOID Tables_Convert_CMYKToRGB(L_UCHAR *pInput, L_UCHAR *pOutput, L_INT nWidth)
{
   HANDLE ClrHandle /*Color Handle*/;
   CONVERSION_PARAMS params  /*Conversion options*/;

   ZeroMemory(&params, sizeof(CONVERSION_PARAMS));

   /*Conversion with options.
     The conversion will be done with the options specified in the
     params variable
   */

   /* set the params size */
   params.uStructSize = sizeof(CONVERSION_PARAMS);

   /* we want to use custom emulation tables */
   params.nMethod = USE_CUSTOM_ET;

   /* set the active conversion method */
   params.nActiveMethod = USE_CUSTOM_ET;

   /* set the emulation tables */
                lstrcpy(params.sDstInputTable, TEXT("C:\\RGBImage.tif"));

   /* initialize the color conversion */
   L_ClrInit (&ClrHandle, /*pointer to color handle to be returned*/
             CCS_CMYK, /*input color space*/
             CCS_RGB, /*output color space*/
             &params /*pointer to the initialization options*/
            );

   /* convert the image buffer */

   L_ClrConvert (ClrHandle, /* conversion handle */
                pInput, /* input buffer */
                pOutput, /* output buffer */
                nWidth, /*pixel's width*/
                nHeight, /*pixel's height*/
                0, /* 0 bytes align*/
                0); /*0 bytes align*/

   /* free the conversion */
   L_ClrFree (ClrHandle);
}