/*
 * xgifload.c  -  based strongly on...
 *
 * gif2ras.c - Converts from a Compuserve GIF (tm) image to a Sun Raster image.
 *
 * Copyright (c) 1988, 1989 by Patrick J. Naughton
 *
 * Author: Patrick J. Naughton
 * naughton@wind.sun.com
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appear in all copies and that
 * both that copyright notice and this permission notice appear in
 * supporting documentation.
 *
 * This file is provided AS IS with no warranties of any kind.  The author
 * shall have no liability with respect to the infringement of copyrights,
 * trade secrets or any patents by this file or any part thereof.  In no
 * event will the author be liable for any lost revenue or profits or
 * other special, indirect and consequential damages.
 *
 */

/*
 *  This file was included with the motifgif example which was provided by 
 *  HP along with the HP-UX 8.05 Motif development fileset (if I remember it
 *  correctly) and was modified for use with Xm++ by B. Strassl (July 1992)
 */

#include "xgif.h"

typedef int boolean;

#define NEXTBYTE (*ptr++)
#define IMAGESEP 0x2c
#define INTERLACEMASK 0x40
#define COLORMAPMASK 0x80

FILE *fp;

int BitOffset = 0,		/* Bit Offset of next code */
    XC = 0, YC = 0,		/* Output X and Y coords of current pixel */
    Pass = 0,			/* Used by output routine if interlaced pic */
    OutCount = 0,		/* Decompressor output 'stack count' */
    RWidth, RHeight,		/* screen dimensions */
    Width, Height,		/* image dimensions */
    LeftOfs, TopOfs,		/* image offset */
    BitsPerPixel,		/* Bits per pixel, read from GIF header */
    BytesPerScanline,		/* bytes per scanline in output raster */
    ColorMapSize,		/* number of colors */
    Background,			/* background color */
    CodeSize,			/* Code size, read from GIF header */
    InitCodeSize,		/* Starting code size, used during Clear */
    Code,			/* Value returned by ReadCode */
    MaxCode,			/* limiting value for current code size */
    ClearCode,			/* GIF clear code */
    EOFCode,			/* GIF end-of-information code */
    CurCode, OldCode, InCode,	/* Decompressor variables */
    FirstFree,			/* First free code, generated per GIF spec */
    FreeCode,			/* Decompressor, next free slot in hash table */
    FinChar,			/* Decompressor variable */
    BitMask,			/* AND mask for data size */
    ReadMask;			/* Code AND mask for current code size */

boolean Interlace, HasColormap;
boolean Verbose = False;

byte *Image;			/* The result array */
byte *RawGIF;			/* The heap array to hold it, raw */
byte *Raster;			/* The raster data stream, unblocked */

    /* The hash table used by the decompressor */
int Prefix[4096];
int Suffix[4096];

    /* An output array used by the decompressor */
int OutCode[1025];

    /* The color map, read from the GIF header */
byte Red[256], Green[256], Blue[256], used[256];
int  numused;

char *id = "GIF87a";

/******************************/
void xmInit()
/******************************/
{
	theScreen = DefaultScreen(theDisp); 
	dispcells = DisplayCells(theDisp, theScreen);
	theCmap = DefaultColormap(theDisp, theScreen);
	rootW = RootWindow(theDisp,theScreen);
	theGC = DefaultGC(theDisp,theScreen);
	fcol = WhitePixel(theDisp,theScreen);
	bcol = BlackPixel(theDisp,theScreen);
	theVisual = DefaultVisual(theDisp,theScreen);
	strip = 0;
	nostrip = 1;
	cmd = "xmGif";

	BitOffset = 0;
    XC = 0; YC = 0;
    Pass = 0;
    OutCount = 0;

	loadOk = 1;
}

void FatalError(msg)
  char* msg;
{
	fprintf(stderr, "xmGif error: %s\n", msg);
	loadOk = 0;
}

/*****************************/
LoadGIF(fname)
  char *fname;
/*****************************/
{
    int            filesize;
    register byte  ch, ch1;
    register byte *ptr, *ptr1;
    register int   i;

	xmInit();

    if (strcmp(fname,"-")==0) { fp = stdin;  fname = "<stdin>"; }
                         else fp = fopen(fname,"r");

    if (!fp) FatalError("file not found");

    /* find the size of the file */
    fseek(fp, 0L, 2);
    filesize = ftell(fp);
    fseek(fp, 0L, 0);

    if (!(ptr = RawGIF = (byte *) malloc(filesize)))
	FatalError("not enough memory to read gif file");

    if (!(Raster = (byte *) malloc(filesize)))
	FatalError("not enough memory to read gif file");

    if (fread(ptr, filesize, 1, fp) != 1)
	FatalError("GIF data read failed");

    if (strncmp(ptr, id, 6))
	FatalError("not a GIF file");

    ptr += 6;

/* Get variables from the GIF screen descriptor */

    ch = NEXTBYTE;
    RWidth = ch + 0x100 * NEXTBYTE;	/* screen dimensions... not used. */
    ch = NEXTBYTE;
    RHeight = ch + 0x100 * NEXTBYTE;

    if (Verbose)
	fprintf(stderr, "screen dims: %dx%d.\n", RWidth, RHeight);

    ch = NEXTBYTE;
    HasColormap = ((ch & COLORMAPMASK) ? True : False);

    BitsPerPixel = (ch & 7) + 1;
    numcols = ColorMapSize = 1 << BitsPerPixel;
    BitMask = ColorMapSize - 1;

    Background = NEXTBYTE;		/* background color... not used. */

    if (NEXTBYTE)		/* supposed to be NULL */
	FatalError("corrupt GIF file (bad screen descriptor)");


/* Read in global colormap. */

    if (HasColormap) {
	if (Verbose)
	    fprintf(stderr, "%s is %dx%d, %d bits per pixel, (%d colors).\n",
		fname, Width,Height,BitsPerPixel, ColorMapSize);
	for (i = 0; i < ColorMapSize; i++) {
	    Red[i] = NEXTBYTE;
	    Green[i] = NEXTBYTE;
	    Blue[i] = NEXTBYTE;
            used[i] = 0;
	    }
        numused = 0;

        }

    else {  /* no colormap in GIF file */
        fprintf(stderr,"%s:  warning!  no colortable in this file.  Winging it.\n",cmd);
        if (!numcols) numcols=256;
        for (i=0; i<numcols; i++) cols[i] = (unsigned long) i;
        }

/* Check for image seperator */

    if (NEXTBYTE != IMAGESEP)
	FatalError("corrupt GIF file (no image separator)");

/* Now read in values from the image descriptor */

    ch = NEXTBYTE;
    LeftOfs = ch + 0x100 * NEXTBYTE;
    ch = NEXTBYTE;
    TopOfs = ch + 0x100 * NEXTBYTE;
    ch = NEXTBYTE;
    Width = ch + 0x100 * NEXTBYTE;
    ch = NEXTBYTE;
    Height = ch + 0x100 * NEXTBYTE;
    Interlace = ((NEXTBYTE & INTERLACEMASK) ? True : False);
/*
    if (Verbose)
	fprintf(stderr, "Reading a %d by %d %sinterlaced image...",
		Width, Height, (Interlace) ? "" : "non-");

    else 
        fprintf(stderr, "%s:  %s is %dx%d, %d colors  ",
	   cmd, fname, Width,Height,ColorMapSize);
*/

/* Note that I ignore the possible existence of a local color map.
 * I'm told there aren't many files around that use them, and the spec
 * says it's defined for future use.  This could lead to an error
 * reading some files. 
 */

/* Start reading the raster data. First we get the intial code size
 * and compute decompressor constant values, based on this code size.
 */

    CodeSize = NEXTBYTE;
    ClearCode = (1 << CodeSize);
    EOFCode = ClearCode + 1;
    FreeCode = FirstFree = ClearCode + 2;

/* The GIF spec has it that the code size is the code size used to
 * compute the above values is the code size given in the file, but the
 * code size used in compression/decompression is the code size given in
 * the file plus one. (thus the ++).
 */

    CodeSize++;
    InitCodeSize = CodeSize;
    MaxCode = (1 << CodeSize);
    ReadMask = MaxCode - 1;

/* Read the raster data.  Here we just transpose it from the GIF array
 * to the Raster array, turning it from a series of blocks into one long
 * data stream, which makes life much easier for ReadCode().
 */

    ptr1 = Raster;
    do {
	ch = ch1 = NEXTBYTE;
	while (ch--) *ptr1++ = NEXTBYTE;
	if ((Raster - ptr1) > filesize)
	    FatalError("corrupt GIF file (unblock)");
    } while(ch1);

    free(RawGIF);		/* We're done with the raw data now... */

    if (Verbose) {
	fprintf(stderr, "done.\n");
	fprintf(stderr, "Decompressing...");
    }


/* Allocate the X Image */
    Image = (byte *) malloc(Width*Height);
    if (!Image) FatalError("not enough memory for XImage");

    theImage = XCreateImage(theDisp,theVisual,8,ZPixmap,0,Image,
                         Width,Height,8,Width);
    if (!theImage) FatalError("unable to create XImage");

    BytesPerScanline = Width;


/* Decompress the file, continuing until you see the GIF EOF code.
 * One obvious enhancement is to add checking for corrupt files here.
 */

    Code = ReadCode();
    while (Code != EOFCode) {

/* Clear code sets everything back to its initial value, then reads the
 * immediately subsequent code as uncompressed data.
 */

	if (Code == ClearCode) {
	    CodeSize = InitCodeSize;
	    MaxCode = (1 << CodeSize);
	    ReadMask = MaxCode - 1;
	    FreeCode = FirstFree;
	    CurCode = OldCode = Code = ReadCode();
	    FinChar = CurCode & BitMask;
	    AddToPixel(FinChar);
	}
	else {

/* If not a clear code, then must be data: save same as CurCode and InCode */

	    CurCode = InCode = Code;

/* If greater or equal to FreeCode, not in the hash table yet;
 * repeat the last character decoded
 */

	    if (CurCode >= FreeCode) {
		CurCode = OldCode;
		OutCode[OutCount++] = FinChar;
	    }

/* Unless this code is raw data, pursue the chain pointed to by CurCode
 * through the hash table to its end; each code in the chain puts its
 * associated output code on the output queue.
 */

	    while (CurCode > BitMask) {
		if (OutCount > 1024) {
		    fprintf(stderr,"\nCorrupt GIF file (OutCount)!\n");
                    _exit(-1);  /* calling 'exit(-1)' dumps core, so I don't */
                    }
		OutCode[OutCount++] = Suffix[CurCode];
		CurCode = Prefix[CurCode];
	    }

/* The last code in the chain is treated as raw data. */

	    FinChar = CurCode & BitMask;
	    OutCode[OutCount++] = FinChar;

/* Now we put the data out to the Output routine.
 * It's been stacked LIFO, so deal with it that way...
 */

	    for (i = OutCount - 1; i >= 0; i--)
		AddToPixel(OutCode[i]);
	    OutCount = 0;

/* Build the hash table on-the-fly. No table is stored in the file. */

	    Prefix[FreeCode] = OldCode;
	    Suffix[FreeCode] = FinChar;
	    OldCode = InCode;

/* Point to the next slot in the table.  If we exceed the current
 * MaxCode value, increment the code size unless it's already 12.  If it
 * is, do nothing: the next code decompressed better be CLEAR
 */

	    FreeCode++;
	    if (FreeCode >= MaxCode) {
		if (CodeSize < 12) {
		    CodeSize++;
		    MaxCode *= 2;
		    ReadMask = (1 << CodeSize) - 1;
		}
	    }
	}
	Code = ReadCode();
    }

    free(Raster);
/*
    if (Verbose)
	fprintf(stderr, "done.\n");
    else
        fprintf(stderr,"(of which %d are used)\n",numused);
*/
    if (fp != stdin)
	fclose(fp);

    ColorDicking(fname);
}


/* Fetch the next code from the raster data stream.  The codes can be
 * any length from 3 to 12 bits, packed into 8-bit bytes, so we have to
 * maintain our location in the Raster array as a BIT Offset.  We compute
 * the byte Offset into the raster array by dividing this by 8, pick up
 * three bytes, compute the bit Offset into our 24-bit chunk, shift to
 * bring the desired code to the bottom, then mask it off and return it. 
 */
ReadCode()
{
int RawCode, ByteOffset;

    ByteOffset = BitOffset / 8;
    RawCode = Raster[ByteOffset] + (0x100 * Raster[ByteOffset + 1]);
    if (CodeSize >= 8)
	RawCode += (0x10000 * Raster[ByteOffset + 2]);
    RawCode >>= (BitOffset % 8);
    BitOffset += CodeSize;
    return(RawCode & ReadMask);
}


AddToPixel(Index)
byte Index;
{
    if (YC<Height)
        *(Image + YC * BytesPerScanline + XC) = Index;

    if (!used[Index]) { used[Index]=1;  numused++; }

/* Update the X-coordinate, and if it overflows, update the Y-coordinate */

    if (++XC == Width) {

/* If a non-interlaced picture, just increment YC to the next scan line. 
 * If it's interlaced, deal with the interlace as described in the GIF
 * spec.  Put the decoded scan line out to the screen if we haven't gone
 * past the bottom of it
 */

	XC = 0;
	if (!Interlace) YC++;
	else {
	    switch (Pass) {
		case 0:
		    YC += 8;
		    if (YC >= Height) {
			Pass++;
			YC = 4;
		    }
		break;
		case 1:
		    YC += 8;
		    if (YC >= Height) {
			Pass++;
			YC = 2;
		    }
		break;
		case 2:
		    YC += 4;
		    if (YC >= Height) {
			Pass++;
			YC = 1;
		    }
		break;
		case 3:
		    YC += 2;
		break;
		default:
		break;
	    }
	}
    }
}



/*************************/
ColorDicking(fname)
char *fname;
{
    /* we've got the picture loaded, we know what colors are needed. get 'em */

    register int   i,j;
    static byte    lmasks[8] = {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80};
    byte           lmask, *ptr;


    if (!HasColormap) return;
    /* no need to allocate any colors if no colormap in GIF file */

    /* Allocate the X colors for this picture */

    if (nostrip)  {   /* nostrip was set.  try REAL hard to do it */
        for (i=j=0; i<numcols; i++) {
            if (used[i]) {
                defs[i].red   = Red[i]<<8;
                defs[i].green = Green[i]<<8;
                defs[i].blue  = Blue[i]<<8;
                defs[i].flags = DoRed | DoGreen | DoBlue;
                if (!XAllocColor(theDisp,theCmap,&defs[i])) { 
                    j++;  defs[i].pixel = 0xffff;
                    }
                cols[i] = defs[i].pixel;
                }
            }

        if (j) {		/* failed to pull it off */
            XColor ctab[256];
            int    dc;

            dc = (dispcells<256) ? dispcells : 256;

            fprintf(stderr,"failed to allocate %d out of %d colors.  Trying extra hard.\n",j,numused);

            /* read in the color table */
            for (i=0; i<dc; i++) ctab[i].pixel = i;
            XQueryColors(theDisp,theCmap,ctab,dc);
                
            /* run through the used colors.  any used color that has a pixel
               value of 0xffff wasn't allocated.  for such colors, run through
               the entire X colormap and pick the closest color */

            for (i=0; i<numcols; i++)
                if (used[i] && cols[i]==0xffff) {  /* an unallocated pixel */
                    int d, mdist, close;
                    unsigned long r,g,b;

                    mdist = 100000;   close = -1;
                    r =  Red[i];
                    g =  Green[i];
                    b =  Blue[i];
                    for (j=0; j<dc; j++) {
                        d = abs(r - (ctab[j].red>>8)) +
                            abs(g - (ctab[j].green>>8)) +
                            abs(b - (ctab[j].blue>>8));
                        if (d<mdist) { mdist=d; close=j; }
                        }
                    if (close<0) FatalError("simply can't do it.  Sorry.");
                    bcopy(&defs[close],&defs[i],sizeof(XColor));
                    cols[i] = ctab[close].pixel;
                    }
            }	/* end 'failed to pull it off' */
        }

    else {          /* strip wasn't set, do the best auto-strip */
        j = 0;
        while (strip<8) {
            lmask = lmasks[strip];
            for (i=0; i<numcols; i++)
                if (used[i]) {
                    defs[i].red   = (Red[i]  &lmask)<<8;
                    defs[i].green = (Green[i]&lmask)<<8;
                    defs[i].blue  = (Blue[i] &lmask)<<8;
                    defs[i].flags = DoRed | DoGreen | DoBlue;
                    if (!XAllocColor(theDisp,theCmap,&defs[i])) break;
                    cols[i] = defs[i].pixel;
                    }

            if (i<numcols) {		/* failed */
                strip++;  j++;
                for (i--; i>=0; i--)
                    if (used[i]) XFreeColors(theDisp,theCmap,cols+i,1,0L);
                }
            else break;
            }

        if (j && strip<8)
            fprintf(stderr,"%s:  %s stripped %d bits\n",cmd,fname,strip);

        if (strip==8) {
            fprintf(stderr,"UTTERLY failed to allocate the desired colors.\n");
            for (i=0; i<numcols; i++) cols[i]=i;
            }
        }

    ptr = Image;
    for (i=0; i<Height; i++)
        for (j=0; j<Width; j++,ptr++) 
            *ptr = (byte) cols[*ptr];
}
