L_RemapBitmapHue

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_RemapBitmapHue(pBitmap, pMask, pHTable, pSTable, pVTable, uLUTLen)

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.

Returns

Comments

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.. uLUTLen – 1. For example, if uLUTLen = 256

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.

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.

Required DLLs and Libraries

Platforms

Windows 95 / 98 / Me, Windows 2000 / XP.

See Also

Example

// This example changes all green hues (and hues near green) to the hue of crNewColor  
// The example uses the following macros:
#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 TestFunction(pBITMAPHANDLE pBitmap, COLORREF crNewColor)
{
   L_UINT  L_FAR * uMaskTable;
   L_UINT  L_FAR * 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 = malloc (uLUTLen * sizeof(L_UINT));
   uHueTable  = 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);
   if(uMaskTable)
      free(uMaskTable);
   if(uHueTable)
      free (uHueTable);
   return nRet;
}