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gifalloc.c

/*****************************************************************************
*   "Gif-Lib" - Yet another gif library.                         *
*                                                          *
* Written by:  Gershon Elber                    Ver 0.1, Jun. 1989   *
* Extensively hacked by: Eric S. Raymond        Ver 1.?, Sep 1992    *
******************************************************************************
* GIF construction tools                                          *
******************************************************************************
* History:                                                 *
* 15 Sep 92 - Version 1.0 by Eric Raymond.                             *
*****************************************************************************/
#include <stdio.h>
#include "gif_lib.h"

#define MAX(x, y) (((x) > (y)) ? (x) : (y))

/******************************************************************************
* Miscellaneous utility functions                                 *
******************************************************************************/

int BitSize(int n)
/* return smallest bitfield size n will fit in */
{
    register      i;

    for (i = 1; i <= 8; i++)
      if ((1 << i) >= n)
          break;
    return(i);
}


/******************************************************************************
* Color map object functions                                      *
******************************************************************************/

ColorMapObject *MakeMapObject(int ColorCount, GifColorType *ColorMap)
/*
 * Allocate a color map of given size; initialize with contents of
 * ColorMap if that pointer is non-NULL.
 */
{
    ColorMapObject *Object;

    if (ColorCount != (1 << BitSize(ColorCount)))
      return((ColorMapObject *)NULL);

    Object = (ColorMapObject *)malloc(sizeof(ColorMapObject));
    if (Object == (ColorMapObject *)NULL)
      return((ColorMapObject *)NULL);

    Object->Colors = (GifColorType *)calloc(ColorCount, sizeof(GifColorType));
    if (Object->Colors == (GifColorType *)NULL)
      return((ColorMapObject *)NULL);

    Object->ColorCount = ColorCount;
    Object->BitsPerPixel = BitSize(ColorCount);

    if (ColorMap)
      memcpy((char *)Object->Colors,
             (char *)ColorMap, ColorCount * sizeof(GifColorType));

    return(Object);
}

void FreeMapObject(ColorMapObject *Object)
/*
 * Free a color map object
 */
{
    free(Object->Colors);
    free(Object);
}

#ifdef DEBUG
void DumpColorMap(ColorMapObject *Object, FILE *fp)
{
    if (Object)
    {
      int i, j, Len = Object->ColorCount;

      for (i = 0; i < Len; i+=4) {
          for (j = 0; j < 4 && j < Len; j++) {
            fprintf(fp,
                  "%3d: %02x %02x %02x   ", i + j,
                   Object->Colors[i + j].Red,
                   Object->Colors[i + j].Green,
                   Object->Colors[i + j].Blue);
          }
          fprintf(fp, "\n");
      }
    }
}
#endif /* DEBUG */

ColorMapObject *UnionColorMap(
                   ColorMapObject *ColorIn1,
                   ColorMapObject *ColorIn2,
                   GifPixelType ColorTransIn2[])
/*
 * Compute the union of two given color maps and return it.  If result can't 
 * fit into 256 colors, NULL is returned, the allocated union otherwise.
 * ColorIn1 is copied as is to ColorUnion, while colors from ColorIn2 are
 * copied iff they didn't exist before.  ColorTransIn2 maps the old
 * ColorIn2 into ColorUnion color map table.
 */
{
    int i, j, CrntSlot, RoundUpTo, NewBitSize;
    ColorMapObject *ColorUnion;

    /*
     * Allocate table which will hold the result for sure.
     */
    ColorUnion
      = MakeMapObject(MAX(ColorIn1->ColorCount,ColorIn2->ColorCount)*2,NULL);

    if (ColorUnion == NULL)
      return(NULL);

    /* Copy ColorIn1 to ColorUnionSize; */
    for (i = 0; i < ColorIn1->ColorCount; i++)
      ColorUnion->Colors[i] = ColorIn1->Colors[i];
    CrntSlot = ColorIn1->ColorCount;

    /*
     * Potentially obnoxious hack:
     *
     * Back CrntSlot down past all contiguous {0, 0, 0} slots at the end
     * of table 1.  This is very useful if your display is limited to
     * 16 colors.
     */
    while (ColorIn1->Colors[CrntSlot-1].Red == 0
         && ColorIn1->Colors[CrntSlot-1].Green == 0
         && ColorIn1->Colors[CrntSlot-1].Red == 0)
      CrntSlot--;

    /* Copy ColorIn2 to ColorUnionSize (use old colors if they exist): */
    for (i = 0; i < ColorIn2->ColorCount && CrntSlot<=256; i++)
    {
      /* Let's see if this color already exists: */
      for (j = 0; j < ColorIn1->ColorCount; j++)
          if (memcmp(&ColorIn1->Colors[j], &ColorIn2->Colors[i], sizeof(GifColorType)) == 0)
            break;

      if (j < ColorIn1->ColorCount)
          ColorTransIn2[i] = j;     /* color exists in Color1 */
      else
      {
          /* Color is new - copy it to a new slot: */
          ColorUnion->Colors[CrntSlot] = ColorIn2->Colors[i];
          ColorTransIn2[i] = CrntSlot++;
      }
    }

    if (CrntSlot > 256)
    {
      FreeMapObject(ColorUnion);
      return((ColorMapObject *)NULL);
    }

    NewBitSize = BitSize(CrntSlot);
    RoundUpTo = (1 << NewBitSize);

    if (RoundUpTo != ColorUnion->ColorCount)
    {
      register GifColorType   *Map = ColorUnion->Colors;

      /*
       * Zero out slots up to next power of 2.
       * We know these slots exist because of the way ColorUnion's
       * start dimension was computed.
       */
      for (j = CrntSlot; j < RoundUpTo; j++)
          Map[j].Red = Map[j].Green = Map[j].Blue = 0;

      /* perhaps we can shrink the map? */
      if (RoundUpTo < ColorUnion->ColorCount)
          ColorUnion->Colors 
            = (GifColorType *)realloc(Map, sizeof(GifColorType)*RoundUpTo);
    }

    ColorUnion->ColorCount = RoundUpTo;
    ColorUnion->BitsPerPixel = NewBitSize;

    return(ColorUnion);
}

void ApplyTranslation(SavedImage *Image, GifPixelType Translation[])
/*
 * Apply a given color translation to the raster bits of an image
 */
{
    register int i;
    register int RasterSize = Image->ImageDesc.Height * Image->ImageDesc.Width;

    for (i = 0; i < RasterSize; i++)
      Image->RasterBits[i] = Translation[Image->RasterBits[i]];
}

/******************************************************************************
* Extension record functions                                      *
******************************************************************************/

void MakeExtension(SavedImage *New, int Function)
{
    New->Function = Function;
    /*
     * Someday we might have to deal with multiple extensions.
     */
}

int AddExtensionBlock(SavedImage *New, int Len, char ExtData[])
{
    ExtensionBlock      *ep;

    if (New->ExtensionBlocks == NULL)
      New->ExtensionBlocks = (ExtensionBlock *)malloc(sizeof(ExtensionBlock));
    else
      New->ExtensionBlocks =
          (ExtensionBlock *)realloc(New->ExtensionBlocks,
                  sizeof(ExtensionBlock) * (New->ExtensionBlockCount + 1));

    if (New->ExtensionBlocks == NULL)
      return(GIF_ERROR);

    ep = &New->ExtensionBlocks[New->ExtensionBlockCount++];

    if ((ep->Bytes = (char *)malloc(ep->ByteCount = Len)) == NULL)
      return(GIF_ERROR);

    if (ExtData)
      memcpy(ep->Bytes, ExtData, Len);

    return(GIF_OK);
}

void FreeExtension(SavedImage *Image)
{
    ExtensionBlock      *ep;

    for (ep = Image->ExtensionBlocks;
       ep < Image->ExtensionBlocks + Image->ExtensionBlockCount;
       ep++)
      (void) free((char *)ep->Bytes);
    free((char *)Image->ExtensionBlocks);
    Image->ExtensionBlocks = NULL;
}

/******************************************************************************
* Image block allocation functions                                *
******************************************************************************/
SavedImage *MakeSavedImage(GifFileType *GifFile, SavedImage *CopyFrom)
/*
 * Append an image block to the SavedImages array  
 */
{
    SavedImage    *sp;

    if (GifFile->SavedImages == NULL)
      GifFile->SavedImages = (SavedImage *)malloc(sizeof(SavedImage));
    else
      GifFile->SavedImages = (SavedImage *)realloc(GifFile->SavedImages,
                        sizeof(SavedImage) * (GifFile->ImageCount+1));

    if (GifFile->SavedImages == NULL)
      return((SavedImage *)NULL);
    else
    {
      sp = &GifFile->SavedImages[GifFile->ImageCount++];
      memset((char *)sp, '\0', sizeof(SavedImage));

      if (CopyFrom)
      {
          memcpy((char *)sp, CopyFrom, sizeof(SavedImage));

          /*
           * Make our own allocated copies of the heap fields in the
           * copied record.  This guards against potential aliasing
           * problems.
           */

          /* first, the local color map */
          if (sp->ImageDesc.ColorMap)
            sp->ImageDesc.ColorMap =
                MakeMapObject(CopyFrom->ImageDesc.ColorMap->ColorCount,
                          CopyFrom->ImageDesc.ColorMap->Colors);

          /* next, the raster */
          sp->RasterBits = (char *)malloc(sizeof(GifPixelType)
                        * CopyFrom->ImageDesc.Height
                        * CopyFrom->ImageDesc.Width);
          memcpy(sp->RasterBits,
               CopyFrom->RasterBits,
               sizeof(GifPixelType)
                  * CopyFrom->ImageDesc.Height
                  * CopyFrom->ImageDesc.Width);

          /* finally, the extension blocks */
          if (sp->ExtensionBlocks)
          {
            sp->ExtensionBlocks
                = (ExtensionBlock*)malloc(sizeof(ExtensionBlock)
                                    * CopyFrom->ExtensionBlockCount);
            memcpy(sp->ExtensionBlocks,
               CopyFrom->ExtensionBlocks,
               sizeof(ExtensionBlock)
                  * CopyFrom->ExtensionBlockCount);

            /*
             * For the moment, the actual blocks can take their
             * chances with free().  We'll fix this later. 
             */
          }
      }

      return(sp);
    }
}

void FreeSavedImages(GifFileType *GifFile)
{
    SavedImage    *sp;

    for (sp = GifFile->SavedImages;
       sp < GifFile->SavedImages + GifFile->ImageCount;
       sp++)
    {
      if (sp->ImageDesc.ColorMap)
          FreeMapObject(sp->ImageDesc.ColorMap);

      if (sp->RasterBits)
          free((char *)sp->RasterBits);

      if (sp->ExtensionBlocks)
          FreeExtension(sp);
    }
    free((char *) GifFile->SavedImages);
}




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