L_RemapBitmapHue

#include "l_bitmap.h"

L_LTIMGCLR_API L_INT L_RemapBitmapHue(pBitmap, pMask, pHTable, pSTable, pVTable, uLUTLen, uFlags)

Uses a lookup table to change a bitmap's hue values. The saturation and value tables change S and V values only if a particular hue value is marked as non-zero in the pMask table. It is used for all resolutions, including 48 and 64-bit images.

Parameters

pBITMAPHANDLE pBitmap

Pointer to a bitmap handle that references the bitmap to convert.

L_UINT * pMask

Lookup table that identifies which values in the pHTable, pSTable and pVTable are valid. If pMask[i] is non-zero, then pHTable, pSTable and pVTable` are to be used. If pMask[i] is 0 then pHTable, pSTable and pVTable are ignored. If pMask is NULL, all entries in the pHTable, pSTable and pVTable are used.

L_UINT * pHTable

Hue look up table. If the pMask table value for a particular pixel hue is non-zero, then the hue is changed to the corresponding entry in pHTable. For example, if a pixel value has a hue of 85 and pMask[85] is non-zero, the hue is changed to pHTable[85]. If pHTable is NULL, the hue of each pixel is unchanged.

L_UINT * pSTable

Saturation look up table. If the pMask table value for a particular pixel hue is non-zero, then the saturation is changed to the corresponding entry in pSTable. For example, if a pixel value has a hue of 85 and pMask[85] is non-zero, the saturation is changed to pSTable[85]. If pHTable is NULL, the saturation is changed to pSTable[85]. If pSTable is NULL, the saturation of each pixel is unchanged.

L_UINT * pVTable

Value look up table. If the pMask table value for a particular pixel hue is non-zero, then the value is changed to the corresponding entry in pVTable. For example, if a pixel value has a hue of 85 and pMask[85] is non-zero, the value is changed to pVTable[85]. If pHTable is NULL, the value is changed to pVTable[85]. If pVTable is NULL, the value of each pixel is unchanged.

L_UINT uLUTLen

Length of the lookup table. Possible values are:

L_UINT32 uFlags

Reserved for future use. Must be 0.

Returns

Comments

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

This function can be used to change a range of colors to another range of colors. For example, it could be used to change all red pixels to any color, where a red pixel can have any brightness (V) and any amount of white (saturation). A red pixel in this case would be

RGB(x,y,y) where:

0<=x<(uLUTLen - 1) and 

0<=y<x

or in the HSV color space

HSV(0,x,x) where :

0<=x<=(uLUTLen - 1)

The pMask lookup table identifies which values in the pHTable are valid. If a pMask value is 0, then the corresponding value in the pHTable is ignored. If a pMask value is non-zero, then the corresponding value in the pHTable is used. For example, if a pixel has a hue value of 240 and pMask[240] is nonzero, then the hue value of 240 is replaced with pHTable[240]. Traditionally, hue ranges from 0 to 359. For the lookup table, the range of 0 to 359 is remapped to a range of 0 to uLUTLen - 1. For example, if uLUTLen = 256

To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.

Use L_RGBtoHSV() and L_HSVtoRGB to convert between RGB and HSV colorspace.

This function supports 48 and 64-bit colored images.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

Required DLLs and Libraries

• LTIMGCLR
• 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.

#define INCREMENT(x, uLUTLen) ((x+1)% uLUTLen) 
#define DECREMENT(x, uLUTLen) ((x+ (uLUTLen - 1))% uLUTLen) 
#define ADD(x,y, uLUTLen)     ((x+y)% uLUTLen) 
 
L_INT RemapBitmapHueExample(pBITMAPHANDLE pBitmap, COLORREF crNewColor) 
{ 
	/* Load an pass a 24-bit image */ 
 
   L_UINT  * uMaskTable; 
   L_UINT  * uHueTable; 
   HSVREF  hsvRef; 
   L_UINT uHueGreen, uHueChange; 
   L_INT   iHueChange; 
   L_INT   i, iCount, nRet, uLUTLen; 
 
   if(pBitmap->BitsPerPixel >= 48) 
      uLUTLen = 0x10000; 
   else if(!ISGRAY(pBitmap)) 
      uLUTLen = 256; 
   else if(pBitmap->pLUT && pBitmap->Flags.UseLUT) 
      uLUTLen = 256; 
   else 
      uLUTLen = (1 << pBitmap->BitsPerPixel); 
 
   //Allocate tables 
   uMaskTable = (L_UINT *)  malloc (uLUTLen * sizeof(L_UINT)); 
   uHueTable  =(L_UINT *) malloc (uLUTLen * sizeof(L_UINT)); 
 
   //Initialize tables 
   for (i=0; i<uLUTLen; i++) 
   { 
      uMaskTable[i] = 0; 
      uHueTable[i] = i; 
   } 
 
   //Get the hue for green 
   hsvRef = L_RGBtoHSV(RGB(0,255,0)); 
   uHueGreen = hsvRef.uH; 
 
   //Obtain new hue 
   hsvRef = L_RGBtoHSV(crNewColor); 
   iHueChange = (L_INT)hsvRef.uH - (L_INT)uHueGreen; 
   uHueChange = (iHueChange>0) ? (L_UINT)iHueChange : (L_UINT)(iHueChange + (uLUTLen - 1)); 
   uHueGreen   *= (uLUTLen - 1)/255; 
   uHueChange *= (uLUTLen - 1)/255; 
 
   //Set values in uHueTable, uMaskTable  
   uHueTable[uHueGreen] = (uHueTable[uHueGreen] + uHueChange); 
   uMaskTable[uHueGreen] = 1; 
    
   //set the hues near green (+/- 15) 
   iCount = (15 * (uLUTLen - 1))/255; 
   for (i=INCREMENT(uHueGreen,uLUTLen); iCount > 0; i = INCREMENT(i, uLUTLen), iCount--) 
   { 
      uHueTable[i] = ADD(uHueTable[i], uHueChange, uLUTLen); 
      uMaskTable[i] = 1; 
   } 
   iCount = (15 * (uLUTLen - 1))/255; 
   for (i=DECREMENT(uHueGreen, uLUTLen); iCount > 0; i =DECREMENT(i, uLUTLen), iCount--) 
   { 
      uHueTable[i] = ADD(uHueTable[i],uHueChange, uLUTLen); 
      uMaskTable[i] = 1; 
   } 
 
   nRet = L_RemapBitmapHue(pBitmap, uMaskTable, uHueTable, NULL, NULL, uLUTLen, 0); 
   if(nRet !=SUCCESS) 
      return nRet; 
   if(uMaskTable) 
      free(uMaskTable); 
   if(uHueTable) 
      free (uHueTable); 
   return SUCCESS; 
}