dibpal.c

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/*----------------------------------------
   DIBPAL.C -- Palette-Creation Functions
               (c) Charles Petzold, 1998
  ----------------------------------------*/

#include <windows.h>
#include "dibhelp.h"
#include "dibpal.h"

/*------------------------------------------------------------
   DibPalDibTable: Creates a palette from the DIB color table
  ------------------------------------------------------------*/

HPALETTE DibPalDibTable (HDIB hdib)
{
     HPALETTE     hPalette ;
     int          i, iNum ;
     LOGPALETTE * plp ;
     RGBQUAD      rgb ;

     if (0 == (iNum = DibNumColors (hdib)))
          return NULL ;

     plp = malloc (sizeof (LOGPALETTE) + (iNum - 1) * sizeof (PALETTEENTRY)) ;

     plp->palVersion    = 0x0300 ;
     plp->palNumEntries = iNum ;

     for (i = 0 ; i < iNum ; i++)
     {
          DibGetColor (hdib, i, &rgb) ;

          plp->palPalEntry[i].peRed   = rgb.rgbRed ;
          plp->palPalEntry[i].peGreen = rgb.rgbGreen ;
          plp->palPalEntry[i].peBlue  = rgb.rgbBlue ;
          plp->palPalEntry[i].peFlags = 0 ;
     }
     hPalette = CreatePalette (plp) ;
     free (plp) ;
     return hPalette ;
}

/*------------------------------------------------------------------------
   DibPalAllPurpose: Creates a palette suitable for a wide variety
          of images; the palette has 247 entries, but 15 of them are 
          duplicates or match the standard 20 colors.
  ------------------------------------------------------------------------*/

HPALETTE DibPalAllPurpose (void)
{
     HPALETTE     hPalette ;
     int          i, incr, R, G, B ;
     LOGPALETTE * plp ;

     plp = malloc (sizeof (LOGPALETTE) + 246 * sizeof (PALETTEENTRY)) ;

     plp->palVersion    = 0x0300 ;
     plp->palNumEntries = 247 ;

          // The following loop calculates 31 grays shades, but 3 of them
          //        will match the standard 20 colors

     for (i = 0, G = 0, incr = 8 ; G <= 0xFF ; i++, G += incr)
     {
          plp->palPalEntry[i].peRed   = (BYTE) G ;
          plp->palPalEntry[i].peGreen = (BYTE) G ;
          plp->palPalEntry[i].peBlue  = (BYTE) G ;
          plp->palPalEntry[i].peFlags = 0 ;

          incr = (incr == 9 ? 8 : 9) ;
     }

          // The following loop is responsible for 216 entries, but 8 of 
          //        them will match the standard 20 colors, and another
          //        4 of them will match the gray shades above.

     for (R = 0 ; R <= 0xFF ; R += 0x33)
     for (G = 0 ; G <= 0xFF ; G += 0x33)
     for (B = 0 ; B <= 0xFF ; B += 0x33)
     {
          plp->palPalEntry[i].peRed   = (BYTE) R ;
          plp->palPalEntry[i].peGreen = (BYTE) G ;
          plp->palPalEntry[i].peBlue  = (BYTE) B ;
          plp->palPalEntry[i].peFlags = 0 ;

          i++ ;
     }
     hPalette = CreatePalette (plp) ;

     free (plp) ;
     return hPalette ;
}

/*------------------------------------------------------------------------
   DibPalUniformGrays:  Creates a palette of iNum grays, uniformly spaced
  ------------------------------------------------------------------------*/

HPALETTE DibPalUniformGrays (int iNum)
{
     HPALETTE     hPalette ;
     int          i ;
     LOGPALETTE * plp ;

     plp = malloc (sizeof (LOGPALETTE) + (iNum - 1) * sizeof (PALETTEENTRY)) ;

     plp->palVersion    = 0x0300 ;
     plp->palNumEntries = iNum ;

     for (i = 0 ; i < iNum ; i++)
     {
          plp->palPalEntry[i].peRed   =
          plp->palPalEntry[i].peGreen = 
          plp->palPalEntry[i].peBlue  = (BYTE) (i * 255 / (iNum - 1)) ;
          plp->palPalEntry[i].peFlags = 0 ;
     }
     hPalette = CreatePalette (plp) ;
     free (plp) ;
     return hPalette ;
}

/*------------------------------------------------------------------------
   DibPalUniformColors: Creates a palette of iNumR x iNumG x iNumB colors
  ------------------------------------------------------------------------*/

HPALETTE DibPalUniformColors (int iNumR, int iNumG, int iNumB)
{
     HPALETTE     hPalette ;
     int          i, iNum, R, G, B ;
     LOGPALETTE * plp ;

     iNum = iNumR * iNumG * iNumB ;

     plp = malloc (sizeof (LOGPALETTE) + (iNum - 1) * sizeof (PALETTEENTRY)) ;

     plp->palVersion    = 0x0300 ;
     plp->palNumEntries = iNumR * iNumG * iNumB ;

     i = 0 ;
     for (R = 0 ; R < iNumR ; R++)
     for (G = 0 ; G < iNumG ; G++)
     for (B = 0 ; B < iNumB ; B++)
     {
          plp->palPalEntry[i].peRed   = (BYTE) (R * 255 / (iNumR - 1)) ;
          plp->palPalEntry[i].peGreen = (BYTE) (G * 255 / (iNumG - 1)) ;
          plp->palPalEntry[i].peBlue  = (BYTE) (B * 255 / (iNumB - 1)) ;
          plp->palPalEntry[i].peFlags = 0 ;

          i++ ;
     }
     hPalette = CreatePalette (plp) ;
     free (plp) ;
     return hPalette ;
}

/*---------------------------------------------------------------
   DibPalVga:  Creates a palette based on standard 16 VGA colors
  ---------------------------------------------------------------*/

HPALETTE DibPalVga (void)
{
     static RGBQUAD rgb [16] = { 0x00, 0x00, 0x00, 0x00,
                                 0x00, 0x00, 0x80, 0x00,
                                 0x00, 0x80, 0x00, 0x00,
                                 0x00, 0x80, 0x80, 0x00,
                                 0x80, 0x00, 0x00, 0x00,
                                 0x80, 0x00, 0x80, 0x00,
                                 0x80, 0x80, 0x00, 0x00,
                                 0x80, 0x80, 0x80, 0x00,
                                 0xC0, 0xC0, 0xC0, 0x00,
                                 0x00, 0x00, 0xFF, 0x00,
                                 0x00, 0xFF, 0x00, 0x00,
                                 0x00, 0xFF, 0xFF, 0x00,
                                 0xFF, 0x00, 0x00, 0x00,
                                 0xFF, 0x00, 0xFF, 0x00,
                                 0xFF, 0xFF, 0x00, 0x00,
                                 0xFF, 0xFF, 0xFF, 0x00 } ;
     HPALETTE       hPalette ;
     int            i ;
     LOGPALETTE   * plp ;

     plp = malloc (sizeof (LOGPALETTE) + 15 * sizeof (PALETTEENTRY)) ;

     plp->palVersion    = 0x0300 ;
     plp->palNumEntries = 16 ;

     for (i = 0 ; i < 16 ; i++)
     {
          plp->palPalEntry[i].peRed   = rgb[i].rgbRed ;
          plp->palPalEntry[i].peGreen = rgb[i].rgbGreen ;
          plp->palPalEntry[i].peBlue  = rgb[i].rgbBlue ;
          plp->palPalEntry[i].peFlags = 0 ;
     }
     hPalette = CreatePalette (plp) ;
     free (plp) ;
     return hPalette ;
}

/*---------------------------------------------
   Macro used in palette optimization routines
  ---------------------------------------------*/

#define PACK_RGB(R,G,B,iRes) ((int) (R) | ((int) (G) <<  (iRes)) |       \
                                          ((int) (B) << ((iRes) + (iRes))))

/*--------------------------------------------------------------------
   AccumColorCounts: Fills up piCount (indexed by a packed RGB color)
     with counts of pixels of that color.
  --------------------------------------------------------------------*/

static void AccumColorCounts (HDIB hdib, int * piCount, int iRes)
{
     int     x, y, cx, cy ;
     RGBQUAD rgb ;

     cx = DibWidth (hdib) ;
     cy = DibHeight (hdib) ;

     for (y = 0 ; y < cy ; y++)
     for (x = 0 ; x < cx ; x++)
     {
          DibGetPixelColor (hdib, x, y, &rgb) ;

          rgb.rgbRed   >>= (8 - iRes) ;
          rgb.rgbGreen >>= (8 - iRes) ;
          rgb.rgbBlue  >>= (8 - iRes) ;

          ++piCount [PACK_RGB (rgb.rgbRed, rgb.rgbGreen, rgb.rgbBlue, iRes)] ;
     }
}

/*--------------------------------------------------------------
   DibPalPopularity:  Popularity algorithm for optimized colors
  --------------------------------------------------------------*/

HPALETTE DibPalPopularity (HDIB hdib, int iRes)
{
     HPALETTE     hPalette ;
     int          i, iArraySize, iEntry, iCount, iIndex, iMask, R, G, B ;
     int        * piCount ;
     LOGPALETTE * plp ;

          // Validity checks
    
     if (DibBitCount (hdib) < 16)
          return NULL ;

     if (iRes < 3 || iRes > 8)
          return NULL ;

          // Allocate array for counting pixel colors

     iArraySize = 1 << (3 * iRes) ;
     iMask = (1 << iRes) - 1 ;

     if (NULL == (piCount = calloc (iArraySize, sizeof (int))))
          return NULL ;

          // Get the color counts

     AccumColorCounts (hdib, piCount, iRes) ;

          // Set up a palette

     plp = malloc (sizeof (LOGPALETTE) + 235 * sizeof (PALETTEENTRY)) ;

     plp->palVersion = 0x0300 ;

     for (iEntry = 0 ; iEntry < 236 ; iEntry++)
     {
          for (i = 0, iCount = 0 ; i < iArraySize ; i++)
               if (piCount[i] > iCount)
               {
                    iCount = piCount[i] ;
                    iIndex = i ;
               }

          if (iCount == 0)
               break ;

          R = (iMask &  iIndex                  ) << (8 - iRes) ;
          G = (iMask & (iIndex >>         iRes )) << (8 - iRes) ;
          B = (iMask & (iIndex >> (iRes + iRes))) << (8 - iRes) ;

          plp->palPalEntry[iEntry].peRed   = (BYTE) R ; 
          plp->palPalEntry[iEntry].peGreen = (BYTE) G ; 
          plp->palPalEntry[iEntry].peBlue  = (BYTE) B ; 
          plp->palPalEntry[iEntry].peFlags = 0 ;

          piCount [iIndex] = 0 ;
     }
          // On exit from the loop iEntry will be the number of stored entries

     plp->palNumEntries = iEntry ;

          // Create the palette, clean up, and return the palette handle

     hPalette = CreatePalette (plp) ;