L_WindowLevelFillLUTExt

Summary

Fills the user-allocated 16-bit LUT with values ranging between the rgbStart and rgbEnd colors according to the selected LUT type.

Syntax

L_LTDIS_API L_INT L_WindowLevelFillLUTExt (pLUT, ulLUTLen, rgbStart, rgbEnd, nLow, nHigh, uLowBit, uHighBit, nMinValue, nMaxValue, nFactor, uFlags)

Parameters

L_RGBQUAD16* pLUT

Pointer to an array to be updated with the RGB quad (i.e., the lookup table).

L_UINT ulLUTLen

The size of pLUT. The minimum size is 2 raised to the power of (uHighBit - uLowBit + 1).

L_RGBQUAD16 rgbStart

Starting color value for the gradient.

L_RGBQUAD16 rgbEnd

Ending color value for the gradient.

L_INT nLow

The low value of the window width, in pixels.

L_INT nHigh

The high value for the window width, in pixels.

L_UINT uLowBit

Value indicating the low bit used for leveling. This is normally 0 and should be less than the uHighBit.

L_UINT uHighBit

Value indicating the high bit used for leveling. This should be greater than or equal to uLowBit and less than 11 for 12-bit grayscale or 15 for 16-bit grayscale.

L_INT nMinValue

The bitmap's minimum value. This value can be obtained by calling L_GetMinMaxVal.

L_INT nMaxValue

The bitmap's maximum value. This value can be obtained by calling L_GetMinMaxVal.

L_INT nFactor

Value that indicates the factor to be applied in the function operation specified in the uFlags parameter. This parameter is used only if uFlags is FILLLUT_EXPONENTIAL, FILLLUT_LOGARITHMIC, or FILLLUT_SIGMOID. If the FILLLUT_EXPONENTIAL or FILLLUT_SIGMOID flag is selected, its value can be any integer (+/-). If the FILLLUT_LOGARITHMIC flag is selected, its value should be >= 0. If nFactor = 0, the lookup table will be filled linearly.

L_UINT uFlags

Flags that indicate how the range is used to fill the LUT and the type of LUT and whether the LUT contains signed or unsigned data. The following flags indicate how the range is used to fill the LUT:

The following flags indicate the LUT type:

The following flags indicate whether the LUT contains signed or unsigned data:

The following flag indicates whether to fill the LUT using only the rgbStart and rgbEnd colors, as is used in applications using DICOM:

Returns

Comments

Use L_WindowLevelFillLUTExt to fill in a 16-bit LUT used by L_WindowLevelExt or L_WindowLevelBitmapExt, according to the LUT type flag. To fill an 8-bit LUT, call L_WindowLevelFillLUT.

L_WindowLevelFillLUTExt and L_WindowLevelFillLUTExt2 are very similar. The methods have the following differences:

1. L_WindowLevelFillLUTExt allows a choice to be made as to whether to fill the LUT the way it is filled by DICOM applications (fill the LUT using only the rgbStart and rgbEnd colors). L_WindowLevelFillLUTExt2 does not check the FILLLUT_DICOM_STYLE flag: it assumes it is always TRUE (fill the LUT using only the pRgbStart and pRgbEnd colors).
2. L_WindowLevelFillLUTExt2 assumes that the “low” and “high” values have already been shifted by the “LowBit”. L_WindowLevelFillLUTExt2 does not.

L_WindowLevelFillLUTExt fills the LUT as follows:

The nFactor parameter is used only for the exponential, logarithmic, and sigmoid functions. Set nFactor to 0 to have the function perform a linear interpolation between the two points nLow and nHigh and store the results in the lookup table, regardless of the value in uFlags.

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

where:

x = the intensity value of the selected point

uStart = the nLow parameter of this function

uEnd = the nHigh parameter of this function

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

where:

x = the intensity value of the selected point

uStart = the nLow parameter of this function

uEnd = the nHigh parameter of this function

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

where:

x = the intensity value of the selected point

uStart = the nLow parameter of this function

uEnd = the nHigh parameter of this function

If uFlags is FILLLUT_LINEAR, the 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.

Allocate the memory for the LUT before calling this function. Calculate the required size with (sizeof(RGBQUAD) * (1<<(pBitmap->HighBit - pBitmap->LowBit + 1))), as shown 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 (0xFFFF, 0xFFFF, 0xFFFF). With this function, any value that falls between the low level and the high level will be mapped to colors between the starting color and the ending color. If you do not want a mapping function, set the starting and ending colors to the same value.

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 the 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. However, you can also use a 16-bit LUT, which offers more precision. Some special video cards and monitors also support using a 16-bit LUT to display grayscale images.

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

Required DLLs and Libraries

• LTDIS
• For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Win32, x64, Linux.

See Also

Functions

• L_WindowLevel
• L_WindowLevelBitmap
• L_WindowLevelBitmapExt
• L_WindowLevelExt
• L_WindowLevelFillLUT
• L_WindowLevelFillLUTExt2

Topics

• Raster Image Functions: Palettes
• Raster Image Functions: Displaying and Printing
• Using Color Values in LEADTOOLS
• Color Halftone and Halftone Images
• Grayscale Images
• Saving Window-Leveled Bitmaps
• Raster Image Functions: Processing an Image

Example

L_INT WindowLevelFillLUTExtExample(pBITMAPHANDLE pBitmap) 
{ 
   L_INT          nRet; 
   L_RGBQUAD16*   pLUT; 
   L_INT          nMin, nMax; 
   L_INT          nLowBit, nHighBit; 
   L_UINT         uSigned; 
   L_RGBQUAD16    rgbRed = { 0xFFFF, 0, 0, 0 }; 
   L_RGBQUAD16    rgbBlue = { 0, 0, 0xFFFF, 0 }; 
 
   /* allocate the lookup table */ 
   pLUT = (L_RGBQUAD16*)malloc(sizeof(L_RGBQUAD16) * (L_INT32)(1 << (pBitmap->HighBit - pBitmap->LowBit + 1))); 
 
   /* get the bitmap's min/max values */ 
   nRet = L_GetMinMaxBits(pBitmap, &nLowBit, &nHighBit, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   nRet = L_GetMinMaxVal(pBitmap, &nMin, &nMax, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   nLowBit = pBitmap->LowBit; 
   nHighBit = pBitmap->HighBit; 
 
   if (pBitmap->Flags.Signed) 
      uSigned = FILLLUT_SIGNED; 
   else 
      uSigned = FILLLUT_UNSIGNED; 
 
   /* fill the LUT with a color gradient */ 
   nRet = L_WindowLevelFillLUTExt(pLUT, 
      1 << (pBitmap->HighBit - pBitmap->LowBit + 1), 
      rgbRed,          /* RED              */ 
      rgbBlue,         /* 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 | uSigned); /* Fill Inside*/ 
   if (nRet != SUCCESS) 
      return nRet; 
 
   /* window level the bitmap using the new LUT */ 
   nRet = L_WindowLevelBitmapExt(pBitmap, 
      nLowBit, 
      nHighBit, 
      pLUT, 
      1 << (pBitmap->HighBit - pBitmap->LowBit + 1), 
      ORDER_BGR, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   /* free the table */ 
   free(pLUT); 
   return SUCCESS; 
}