LBitmap::WindowLevelFillLUT

#include "ltwrappr.h"

static L_INT LBitmap::WindowLevelFillLUT(pLUT, ulLUTLen, crStart, crEnd, nLow, nHigh, uLowBit, uHighBit, nMinValue, nMaxValue, nFactor, uFlags)

Fills the user-allocated LUT with values range between crStart and crEnd colors according to the selected LUT type.

Returns

Comments

Use this function to fill in the LUT used in LBitmap::WindowLevel according to the LUT type flag.

If you select FILLLUT_LINEAR, the LUT will be filled as follows:

The nFactor parameter is used for logarithmic, exponential, and sigmoid functions only. If nFactor = 0 the function performs a linear interpolation between the two points nLow and nHigh, and stores the results in the lookup table, regardless of the value in uFlags.

If uFlag is FILLLUT_EXPONENTIAL the value of nFactor modifies the lookup table values (see figure below) according to the following equations:

Y = uStart + (uEnd uStart) * (exp ((nFactor/10. * (x-uStart))/(uEnd-uStart)) - nFirstValue) / (nLastValue nFirstValue)

where :

nFirstValue = exp(0).

nLastValue = exp(nFactor)

x = the intensity value of the selected point

uStart = the nLow parameter of this function

uEnd = the nHigh parameter of this function

If uFlag is FILLLUT_LOGARITHMIC the value of nFactor modifies the lookup table values (see figure below) according to the following equations:

Y = uStart + (uEnd uStart) * (ln (1 + (nFactor/10. * (x-uStart))/(uEnd- uStart)) - nFirstValue)/ (nLastValue nFirstValue)

where:

nFirstValue = 0.

nLastValue = ln(1 + nFactor)

x = the intensity value of the selected point

uStart = the nLow parameter of this function

uEnd = the nHigh parameter of this function

If uFlag is FILLLUT_SIGMOID the value of nFactor modifies the lookup table values (see figure below)according to the following equations:

Y = uStart + (uEnd uStart) * (1./ (1 + exp(2*nFactor/10. * (x-Center))/(uEnd- uStart)) - nFirstValue)/ (nLastValue nFirstValue)

where:

nFirstValue = 1./(1+exp(2.*nFactor/10.*(nStart - Center)/ (uEnd- uStart))).

nLastValue = 1./(1+exp(2.*nFactor/10.*(nEnd - Center)/ (uEnd- uStart))).

Center = (nEnd + nStart)/2.

x = the intensity value of the selected point

uStart = the nLow parameter of this function

uEnd = the nHigh parameter of this function

If uFlag is FILLLUT_LINEAR, nFactor is ignored. The function fills the lookup table linearly.

Note: This function only works for 12 or 16 bit grayscale images. Trying to use this function with other images will result in an error.

You must allocate the memory for the LUT before calling this function. You can calculate the required size with (sizeof(RGBQUAD) * (1<<(pBitmap->HighBit - pBitmap->LowBit + 1))), as seen in the example below.

For example, suppose you are working with a 12 bit grayscale image. There are 4096 intensity levels in a 12 bit image (2 raised to the 12th power). Normally, the interval between 0 and 4095 for unsigned data would be mapped to colors between (0, 0, 0) and (255, 255, 255). With this function, any value that falls between the low level and the high level will be mapped to colors between the start color and the end color. If you do not want to use mapping, set the start and end colors equal.

If you only want to map the values between 1972 and 3273 (in a 12-bit unsigned image), then set nLow to 1972, set nHigh to 3273, and set FILLLUT_INSIDE option. To map the values less than 1972 and greater than 3273, select the FILLLUT_OUTSIDE option.

LEADTOOLS supports two types of LUTs for 10-16-bit grayscale images (8-bit LUT and 16-bit LUT).  Typical grayscale image display and processing is done using an 8-bit LUT.  But, you can also use a 16-bit LUT, which offers more precision.  Some special video cards and monitors also support display of grayscale images using a 16-bit LUT.

For information on saving bitmaps that have been window leveled, refer to Saving Window-Leveled Bitmaps.

Required DLLs and Libraries

Platforms

Win32, x64.

See Also

Example

#define MAKE_IMAGE_PATH(pFileName) TEXT("C:\\Users\\Public\\Documents\\LEADTOOLS Images\\")pFileName
L_INT LBitmap__WindowLevelFillLUTExample() 
{
   
   RGBQUAD * pLUT;
   L_INT nRet;
   L_INT nMin, nMax;
   L_INT nLowBit, nHighBit;
   LONG fSigned = 0 ;
   LBitmap myBitmap;
   nRet = myBitmap.Load(MAKE_IMAGE_PATH(TEXT("clean.tif")),16,ORDER_GRAY);
   if(nRet != SUCCESS)
      return nRet;
   nRet = myBitmap.GetMinMaxBits(&nLowBit, &nHighBit);
   if(nRet != SUCCESS)
      return nRet;
   nRet = myBitmap.GetMinMaxVal(&nMin, &nMax);
   if(nRet != SUCCESS)
      return nRet;
   /* allocate the lookup table */
   pLUT = (RGBQUAD *)malloc(sizeof(RGBQUAD) * (L_INT32)(1<<(nHighBit - nLowBit + 1)));
    //set the FILLLUT_SIGNED flag for signed images
    fSigned = FILLLUT_UNSIGNED;
    if(myBitmap.IsPixelsSigned())
       fSigned = FILLLUT_SIGNED;
   /* fill the LUT with a color gradient */
  nRet = myBitmap.WindowLevelFillLUT((RGBQUAD *)pLUT,
                               1<<(nHighBit - nLowBit + 1),
                               RGB(255,0,0),    /* RED              */
                               RGB(0,0,255),    /* BLUE             */
                               23000,           /* Starting value   */
                               45000,           /* Ending value     */
                               nLowBit,         /* Bitmap's LowBit  */
                               nHighBit,        /* Bitmap's HighBit */
                               nMin,            /* Bitmap's MinVal  */
                               nMax,            /* Bitmap's MaxVal  */
                               10,   /*nFactor*/
                               FILLLUT_INSIDE|
                               FILLLUT_LINEAR|
                               fSigned         /*  Fill Inside range*/);
  if(nRet !=SUCCESS)
     return nRet;
   /* window level the bitmap using the new LUT */
   nRet = myBitmap.WindowLevelBitmap(nLowBit,
                                nHighBit,
                                (RGBQUAD *)pLUT,
                                1<<(nHighBit - nLowBit + 1),
                                ORDER_BGR);
   if(nRet !=SUCCESS)
      return nRet;
   /* free the table */
   free(pLUT);
   return SUCCESS;
}