Merge pull request #6 from saurabhb17/master

minor additions

1 files changed, 1108 insertions, 0 deletions

diff --git a/potrace/greymap.cpp b/potrace/greymap.cpp
new file mode 100644
index 0000000..203fa1a
--- /dev/null
+++ b/potrace/greymap.cpp
@@ -0,0 +1,1108 @@
+/* Copyright (C) 2001-2007 Peter Selinger.
+ *  This file is part of Potrace. It is free software and it is covered
+ *  by the GNU General Public License. See the file COPYING for details. */
+
+/* $Id: greymap.c 147 2007-04-09 00:44:09Z selinger $ */
+
+/* Routines for manipulating greymaps, including reading pgm files. We
+ *  only deal with greymaps of depth 8 bits. */
+
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <cmath>
+
+#include <greymap.h>
+
+#define INTBITS ( 8 * sizeof(int) )
+
+#define mod( a, n ) ( (a)>=(n) ? (a) % (n) : (a)>=0 ? (a) : (n) - 1 - ( -1 - (a) ) % (n) )
+
+static int gm_readbody_pnm( FILE* f, greymap_t** gmp, int magic );
+static int gm_readbody_bmp( FILE* f, greymap_t** gmp );
+
+/* ---------------------------------------------------------------------- */
+/* basic greymap routines */
+
+/* return new un-initialized greymap. NULL with errno on error */
+
+greymap_t* gm_new( int w, int h )
+{
+    greymap_t* gm;
+    int        errno_save;
+
+    gm = (greymap_t*) malloc( sizeof(greymap_t) );
+    if( !gm )
+    {
+        return NULL;
+    }
+    gm->w   = w;
+    gm->h   = h;
+    gm->map = (signed short int*) malloc( w * h * sizeof(signed short int) );
+    if( !gm->map )
+    {
+        errno_save = errno;
+        free( gm );
+        errno = errno_save;
+        return NULL;
+    }
+    return gm;
+}
+
+
+/* free the given greymap */
+void gm_free( greymap_t* gm )
+{
+    if( gm )
+    {
+        free( gm->map );
+    }
+    free( gm );
+}
+
+
+/* duplicate the given greymap. Return NULL on error with errno set. */
+greymap_t* gm_dup( greymap_t* gm )
+{
+    greymap_t* gm1 = gm_new( gm->w, gm->h );
+
+    if( !gm1 )
+    {
+        return NULL;
+    }
+    memcpy( gm1->map, gm->map, gm->w * gm->h * 2 );
+    return gm1;
+}
+
+
+/* clear the given greymap to color b. */
+void gm_clear( greymap_t* gm, int b )
+{
+    int i;
+
+    if( b==0 )
+    {
+        memset( gm->map, 0, gm->w * gm->h * 2 );
+    }
+    else
+    {
+        for( i = 0; i<gm->w * gm->h; i++ )
+        {
+            gm->map[i] = b;
+        }
+    }
+}
+
+
+/* ---------------------------------------------------------------------- */
+/* routines for reading pnm streams */
+
+/* read next character after whitespace and comments. Return EOF on
+ *  end of file or error. */
+static int fgetc_ws( FILE* f )
+{
+    int c;
+
+    while( 1 )
+    {
+        c = fgetc( f );
+        if( c=='#' )
+        {
+            while( 1 )
+            {
+                c = fgetc( f );
+                if( c=='\n' || c==EOF )
+                {
+                    break;
+                }
+            }
+        }
+        /* space, tab, line feed, carriage return, form-feed */
+        if( c!=' ' && c!='\t' && c!='\r' && c!='\n' && c!=12 )
+        {
+            return c;
+        }
+    }
+}
+
+
+/* skip whitespace and comments, then read a non-negative decimal
+ *  number from a stream. Return -1 on EOF. Tolerate other errors (skip
+ *  bad characters). Do not the read any characters following the
+ *  number (put next character back into the stream) */
+
+static int readnum( FILE* f )
+{
+    int c;
+    int acc;
+
+    /* skip whitespace and comments */
+    while( 1 )
+    {
+        c = fgetc_ws( f );
+        if( c==EOF )
+        {
+            return -1;
+        }
+        if( c>='0' && c<='9' )
+        {
+            break;
+        }
+    }
+
+    /* first digit is already in c */
+    acc = c - '0';
+    while( 1 )
+    {
+        c = fgetc( f );
+        if( c==EOF )
+        {
+            break;
+        }
+        if( c<'0' || c>'9' )
+        {
+            ungetc( c, f );
+            break;
+        }
+        acc *= 10;
+        acc += c - '0';
+    }
+
+    return acc;
+}
+
+
+/* similar to readnum, but read only a single 0 or 1, and do not read
+ *  any characters after it. */
+
+static int readbit( FILE* f )
+{
+    int c;
+
+    /* skip whitespace and comments */
+    while( 1 )
+    {
+        c = fgetc_ws( f );
+        if( c==EOF )
+        {
+            return -1;
+        }
+        if( c>='0' && c<='1' )
+        {
+            break;
+        }
+    }
+
+    return c - '0';
+}
+
+
+/* ---------------------------------------------------------------------- */
+
+/* read a PNM stream: P1-P6 format (see pnm(5)), or a BMP stream, and
+ *  convert the output to a greymap. Return greymap in *gmp. Return 0
+ *  on success, -1 on error with errno set, -2 on bad file format (with
+ *  error message in gm_read_error), and 1 on premature end of file, -3
+ *  on empty file (including files with only whitespace and comments),
+ *  -4 if wrong magic number. If the return value is >=0, *gmp is
+ *  valid. */
+
+const char* gm_read_error = NULL;
+
+int gm_read( FILE* f, greymap_t** gmp )
+{
+    int magic[2];
+
+    /* read magic number. We ignore whitespace and comments before the
+     *  magic, for the benefit of concatenated files in P1-P3 format.
+     *  Multiple P1-P3 images in a single file are not formally allowed
+     *  by the PNM standard, but there is no harm in being lenient. */
+
+    magic[0] = fgetc_ws( f );
+    if( magic[0] == EOF )
+    {
+        /* files which contain only comments and whitespace count as "empty" */
+        return -3;
+    }
+    magic[1] = fgetc( f );
+    if( magic[0] == 'P' && magic[1] >= '1' && magic[1] <= '6' )
+    {
+        return gm_readbody_pnm( f, gmp, magic[1] );
+    }
+    if( magic[0] == 'B' && magic[1] == 'M' )
+    {
+        return gm_readbody_bmp( f, gmp );
+    }
+    return -4;
+}
+
+
+/* ---------------------------------------------------------------------- */
+/* read PNM format */
+
+/* read PNM stream after magic number. Return values as for gm_read */
+static int gm_readbody_pnm( FILE* f, greymap_t** gmp, int magic )
+{
+    greymap_t* gm;
+    int        x, y, i, j, b, b1, sum;
+    int        bpr; /* bytes per row (as opposed to 4*gm->c) */
+    int        w, h, max;
+
+    gm = NULL;
+
+    w = readnum( f );
+    if( w<0 )
+    {
+        goto format_error;
+    }
+
+    h = readnum( f );
+    if( h<0 )
+    {
+        goto format_error;
+    }
+
+    /* allocate greymap */
+    gm = gm_new( w, h );
+    if( !gm )
+    {
+        return -1;
+    }
+
+    /* zero it out */
+    gm_clear( gm, 0 );
+
+    switch( magic )
+    {
+    default:
+        /* not reached */
+        goto format_error;
+
+    case '1':
+        /* read P1 format: PBM ascii */
+
+        for( y = h - 1; y>=0; y-- )
+        {
+            for( x = 0; x<w; x++ )
+            {
+                b = readbit( f );
+                if( b<0 )
+                {
+                    goto eof;
+                }
+                GM_UPUT( gm, x, y, b ? 0 : 255 );
+            }
+        }
+
+        break;
+
+    case '2':
+        /* read P2 format: PGM ascii */
+
+        max = readnum( f );
+        if( max<1 )
+        {
+            goto format_error;
+        }
+
+        for( y = h - 1; y>=0; y-- )
+        {
+            for( x = 0; x<w; x++ )
+            {
+                b = readnum( f );
+                if( b<0 )
+                {
+                    goto eof;
+                }
+                GM_UPUT( gm, x, y, b * 255 / max );
+            }
+        }
+
+        break;
+
+    case '3':
+        /* read P3 format: PPM ascii */
+
+        max = readnum( f );
+        if( max<1 )
+        {
+            goto format_error;
+        }
+
+        for( y = h - 1; y>=0; y-- )
+        {
+            for( x = 0; x<w; x++ )
+            {
+                sum = 0;
+                for( i = 0; i<3; i++ )
+                {
+                    b = readnum( f );
+                    if( b<0 )
+                    {
+                        goto eof;
+                    }
+                    sum += b;
+                }
+
+                GM_UPUT( gm, x, y, sum * (255 / 3) / max );
+            }
+        }
+
+        break;
+
+    case '4':
+        /* read P4 format: PBM raw */
+
+        b = fgetc( f ); /* read single white-space character after height */
+        if( b==EOF )
+        {
+            goto format_error;
+        }
+
+        bpr = (w + 7) / 8;
+
+        for( y = h - 1; y>=0; y-- )
+        {
+            for( i = 0; i<bpr; i++ )
+            {
+                b = fgetc( f );
+                if( b==EOF )
+                {
+                    goto eof;
+                }
+                for( j = 0; j<8; j++ )
+                {
+                    GM_PUT( gm, i * 8 + j, y, b & (0x80 >> j) ? 0 : 255 );
+                }
+            }
+        }
+
+        break;
+
+    case '5':
+        /* read P5 format: PGM raw */
+
+        max = readnum( f );
+        if( max<1 )
+        {
+            goto format_error;
+        }
+
+        b = fgetc( f ); /* read single white-space character after max */
+        if( b==EOF )
+        {
+            goto format_error;
+        }
+
+        for( y = h - 1; y>=0; y-- )
+        {
+            for( x = 0; x<w; x++ )
+            {
+                b = fgetc( f );
+                if( b==EOF )
+                    goto eof;
+                if( max>=256 )
+                {
+                    b <<= 8;
+                    b1  = fgetc( f );
+                    if( b1==EOF )
+                        goto eof;
+                    b |= b1;
+                }
+                GM_UPUT( gm, x, y, b * 255 / max );
+            }
+        }
+
+        break;
+
+    case '6':
+        /* read P6 format: PPM raw */
+
+        max = readnum( f );
+        if( max<1 )
+        {
+            goto format_error;
+        }
+
+        b = fgetc( f ); /* read single white-space character after max */
+        if( b==EOF )
+        {
+            goto format_error;
+        }
+
+        for( y = h - 1; y>=0; y-- )
+        {
+            for( x = 0; x<w; x++ )
+            {
+                sum = 0;
+                for( i = 0; i<3; i++ )
+                {
+                    b = fgetc( f );
+                    if( b==EOF )
+                    {
+                        goto eof;
+                    }
+                    if( max>=256 )
+                    {
+                        b <<= 8;
+                        b1  = fgetc( f );
+                        if( b1==EOF )
+                            goto eof;
+                        b |= b1;
+                    }
+                    sum += b;
+                }
+
+                GM_UPUT( gm, x, y, sum * (255 / 3) / max );
+            }
+        }
+
+        break;
+    }
+
+    *gmp = gm;
+    return 0;
+
+eof:
+    *gmp = gm;
+    return 1;
+
+format_error:
+    gm_free( gm );
+    if( magic == '1' || magic == '4' )
+    {
+        gm_read_error = "invalid pbm file";
+    }
+    else if( magic == '2' || magic == '5' )
+    {
+        gm_read_error = "invalid pgm file";
+    }
+    else
+    {
+        gm_read_error = "invalid ppm file";
+    }
+    return -2;
+}
+
+
+/* ---------------------------------------------------------------------- */
+/* read BMP format */
+
+struct bmp_info_s
+{
+    unsigned int FileSize;
+    unsigned int reserved;
+    unsigned int DataOffset;
+    unsigned int InfoSize;
+    unsigned int w;             /* width */
+    unsigned int h;             /* height */
+    unsigned int Planes;
+    unsigned int bits;          /* bits per sample */
+    unsigned int comp;          /* compression mode */
+    unsigned int ImageSize;
+    unsigned int XpixelsPerM;
+    unsigned int YpixelsPerM;
+    unsigned int ncolors;       /* number of colors in palette */
+    unsigned int ColorsImportant;
+    unsigned int ctbits;        /* sample size for color table */
+};
+typedef struct bmp_info_s bmp_info_t;
+
+/* auxiliary */
+
+static int bmp_count = 0;   /* counter for byte padding */
+static int bmp_pos   = 0;   /* counter from start of BMP data */
+
+/* read n-byte little-endian integer. Return 1 on EOF or error, else
+ *  0. Assume n<=4. */
+static int bmp_readint( FILE* f, int n, unsigned int* p )
+{
+    int          i;
+    unsigned int sum = 0;
+    int          b;
+
+    for( i = 0; i<n; i++ )
+    {
+        b = fgetc( f );
+        if( b==EOF )
+        {
+            return 1;
+        }
+        sum += b << (8 * i);
+    }
+
+    bmp_count += n;
+    bmp_pos   += n;
+    *p = sum;
+    return 0;
+}
+
+
+/* reset padding boundary */
+static void bmp_pad_reset( void )
+{
+    bmp_count = 0;
+}
+
+
+/* read padding bytes to 4-byte boundary. Return 1 on EOF or error,
+ *  else 0. */
+static int bmp_pad( FILE* f )
+{
+    int c, i, b;
+
+    c = (-bmp_count) & 3;
+    for( i = 0; i<c; i++ )
+    {
+        b = fgetc( f );
+        if( b==EOF )
+        {
+            return 1;
+        }
+    }
+
+    bmp_pos  += c;
+    bmp_count = 0;
+    return 0;
+}
+
+
+/* forward to the new file position. Return 1 on EOF or error, else 0 */
+static int bmp_forward( FILE* f, int pos )
+{
+    int b;
+
+    while( bmp_pos < pos )
+    {
+        b = fgetc( f );
+        if( b==EOF )
+        {
+            return 1;
+        }
+        bmp_pos++;
+        bmp_count++;
+    }
+
+    return 0;
+}
+
+
+#define TRY( x )     if( x ) \
+        goto try_error
+#define TRY_EOF( x ) if( x ) \
+        goto eof
+
+/* read BMP stream after magic number. Return values as for gm_read.
+ *  We choose to be as permissive as possible, since there are many
+ *  programs out there which produce BMP. For instance, ppmtobmp can
+ *  produce codings with anywhere from 1-8 or 24 bits per sample,
+ *  although most specifications only allow 1,4,8,24,32. We can also
+ *  read both the old and new OS/2 BMP formats in addition to the
+ *  Windows BMP format. */
+static int gm_readbody_bmp( FILE* f, greymap_t** gmp )
+{
+    bmp_info_t   bmpinfo;
+    int*         coltable;
+    unsigned int b, c;
+    unsigned int i, j;
+    greymap_t*   gm;
+    unsigned int x, y;
+    int          col[2];
+    unsigned int bitbuf;
+    unsigned int n;
+
+    gm_read_error = NULL;
+    gm = NULL;
+    coltable = NULL;
+
+    bmp_pos = 2; /* set file position */
+
+    /* file header (minus magic number) */
+    TRY( bmp_readint( f, 4, &bmpinfo.FileSize ) );
+    TRY( bmp_readint( f, 4, &bmpinfo.reserved ) );
+    TRY( bmp_readint( f, 4, &bmpinfo.DataOffset ) );
+
+    /* info header */
+    TRY( bmp_readint( f, 4, &bmpinfo.InfoSize ) );
+    if( bmpinfo.InfoSize == 40 || bmpinfo.InfoSize == 64 )
+    {
+        /* Windows or new OS/2 format */
+        bmpinfo.ctbits = 32; /* sample size in color table */
+        TRY( bmp_readint( f, 4, &bmpinfo.w ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.h ) );
+        TRY( bmp_readint( f, 2, &bmpinfo.Planes ) );
+        TRY( bmp_readint( f, 2, &bmpinfo.bits ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.comp ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.ImageSize ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.XpixelsPerM ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.YpixelsPerM ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.ncolors ) );
+        TRY( bmp_readint( f, 4, &bmpinfo.ColorsImportant ) );
+    }
+    else if( bmpinfo.InfoSize == 12 )
+    {
+        /* old OS/2 format */
+        bmpinfo.ctbits = 24; /* sample size in color table */
+        TRY( bmp_readint( f, 2, &bmpinfo.w ) );
+        TRY( bmp_readint( f, 2, &bmpinfo.h ) );
+        TRY( bmp_readint( f, 2, &bmpinfo.Planes ) );
+        TRY( bmp_readint( f, 2, &bmpinfo.bits ) );
+        bmpinfo.comp    = 0;
+        bmpinfo.ncolors = 0;
+    }
+    else
+    {
+        goto format_error;
+    }
+
+    /* forward to color table (i.e., if bmpinfo.InfoSize == 64) */
+    TRY( bmp_forward( f, 14 + bmpinfo.InfoSize ) );
+
+    if( bmpinfo.Planes != 1 )
+    {
+        gm_read_error = "cannot handle bmp planes";
+        goto format_error; /* can't handle planes */
+    }
+
+    if( bmpinfo.ncolors == 0 )
+    {
+        bmpinfo.ncolors = 1 << bmpinfo.bits;
+    }
+
+    /* color table, present only if bmpinfo.bits <= 8. */
+    if( bmpinfo.bits <= 8 )
+    {
+        coltable = (int*) malloc( bmpinfo.ncolors * sizeof(int) );
+        if( !coltable )
+        {
+            goto std_error;
+        }
+
+        /* NOTE: since we are reading a greymap, we can immediately convert
+         *  the color table entries to grey values. */
+        for( i = 0; i<bmpinfo.ncolors; i++ )
+        {
+            TRY( bmp_readint( f, bmpinfo.ctbits / 8, &c ) );
+            c = ( (c >> 16) & 0xff ) + ( (c >> 8) & 0xff ) + (c & 0xff);
+            coltable[i] = c / 3;
+        }
+    }
+
+    /* forward to data */
+    if( bmpinfo.InfoSize != 12 ) /* not old OS/2 format */
+    {
+        TRY( bmp_forward( f, bmpinfo.DataOffset ) );
+    }
+
+    /* allocate greymap */
+    gm = gm_new( bmpinfo.w, bmpinfo.h );
+    if( !gm )
+    {
+        goto std_error;
+    }
+
+    /* zero it out */
+    gm_clear( gm, 0 );
+
+    switch( bmpinfo.bits + 0x100 * bmpinfo.comp )
+    {
+    default:
+        goto format_error;
+        break;
+
+    case 0x001: /* monochrome palette */
+
+        /* raster data */
+        for( y = 0; y<bmpinfo.h; y++ )
+        {
+            bmp_pad_reset();
+            for( i = 0; 8 * i<bmpinfo.w; i++ )
+            {
+                TRY_EOF( bmp_readint( f, 1, &b ) );
+                for( j = 0; j<8; j++ )
+                {
+                    GM_PUT( gm, i * 8 + j, y, b & (0x80 >> j) ? coltable[1] : coltable[0] );
+                }
+            }
+
+            TRY( bmp_pad( f ) );
+        }
+
+        break;
+
+    case 0x002: /* 2-bit to 8-bit palettes */
+    case 0x003:
+    case 0x004:
+    case 0x005:
+    case 0x006:
+    case 0x007:
+    case 0x008:
+        for( y = 0; y<bmpinfo.h; y++ )
+        {
+            bmp_pad_reset();
+            bitbuf = 0; /* bit buffer: bits in buffer are high-aligned */
+            n = 0;      /* number of bits currently in bitbuffer */
+            for( x = 0; x<bmpinfo.w; x++ )
+            {
+                if( n < bmpinfo.bits )
+                {
+                    TRY_EOF( bmp_readint( f, 1, &b ) );
+                    bitbuf |= b << (INTBITS - 8 - n);
+                    n += 8;
+                }
+                b = bitbuf >> (INTBITS - bmpinfo.bits);
+                bitbuf <<= bmpinfo.bits;
+                n -= bmpinfo.bits;
+                GM_UPUT( gm, x, y, coltable[b] );
+            }
+
+            TRY( bmp_pad( f ) );
+        }
+
+        break;
+
+    case 0x010: /* 16-bit encoding */
+
+        /* can't do this format because it is not well-documented and I
+         *  don't have any samples */
+        gm_read_error = "cannot handle bmp 16-bit coding";
+        goto format_error;
+        break;
+
+    case 0x018: /* 24-bit encoding */
+    case 0x020: /* 32-bit encoding */
+        for( y = 0; y<bmpinfo.h; y++ )
+        {
+            bmp_pad_reset();
+            for( x = 0; x<bmpinfo.w; x++ )
+            {
+                TRY_EOF( bmp_readint( f, bmpinfo.bits / 8, &c ) );
+                c = ( (c >> 16) & 0xff ) + ( (c >> 8) & 0xff ) + (c & 0xff);
+                GM_UPUT( gm, x, y, c / 3 );
+            }
+
+            TRY( bmp_pad( f ) );
+        }
+
+        break;
+
+    case 0x204: /* 4-bit runlength compressed encoding (RLE4) */
+        x = 0;
+        y = 0;
+        while( 1 )
+        {
+            TRY_EOF( bmp_readint( f, 1, &b ) ); /* opcode */
+            TRY_EOF( bmp_readint( f, 1, &c ) ); /* argument */
+            if( b>0 )
+            {
+                /* repeat count */
+                col[0] = coltable[(c >> 4) & 0xf];
+                col[1] = coltable[c & 0xf];
+                for( i = 0; i<b && x<bmpinfo.w; i++ )
+                {
+                    if( x>=bmpinfo.w )
+                    {
+                        x = 0;
+                        y++;
+                    }
+                    if( y>=bmpinfo.h )
+                    {
+                        break;
+                    }
+                    GM_UPUT( gm, x, y, col[i & 1] );
+                    x++;
+                }
+            }
+            else if( c == 0 )
+            {
+                /* end of line */
+                y++;
+                x = 0;
+            }
+            else if( c == 1 )
+            {
+                /* end of greymap */
+                break;
+            }
+            else if( c == 2 )
+            {
+                /* "delta": skip pixels in x and y directions */
+                TRY_EOF( bmp_readint( f, 1, &b ) ); /* x offset */
+                TRY_EOF( bmp_readint( f, 1, &c ) ); /* y offset */
+                x += b;
+                y += c;
+            }
+            else
+            {
+                /* verbatim segment */
+                for( i = 0; i<c; i++ )
+                {
+                    if( (i & 1)==0 )
+                    {
+                        TRY_EOF( bmp_readint( f, 1, &b ) );
+                    }
+                    if( x>=bmpinfo.w )
+                    {
+                        x = 0;
+                        y++;
+                    }
+                    if( y>=bmpinfo.h )
+                    {
+                        break;
+                    }
+                    GM_PUT( gm, x, y, coltable[( b >> ( 4 - 4 * (i & 1) ) ) & 0xf] );
+                    x++;
+                }
+
+                if( (c + 1) & 2 )
+                {
+                    /* pad to 16-bit boundary */
+                    TRY_EOF( bmp_readint( f, 1, &b ) );
+                }
+            }
+        }
+
+        break;
+
+    case 0x108: /* 8-bit runlength compressed encoding (RLE8) */
+        x = 0;
+        y = 0;
+        while( 1 )
+        {
+            TRY_EOF( bmp_readint( f, 1, &b ) ); /* opcode */
+            TRY_EOF( bmp_readint( f, 1, &c ) ); /* argument */
+            if( b>0 )
+            {
+                /* repeat count */
+                for( i = 0; i<b; i++ )
+                {
+                    if( x>=bmpinfo.w )
+                    {
+                        x = 0;
+                        y++;
+                    }
+                    if( y>=bmpinfo.h )
+                    {
+                        break;
+                    }
+                    GM_UPUT( gm, x, y, coltable[c] );
+                    x++;
+                }
+            }
+            else if( c == 0 )
+            {
+                /* end of line */
+                y++;
+                x = 0;
+            }
+            else if( c == 1 )
+            {
+                /* end of greymap */
+                break;
+            }
+            else if( c == 2 )
+            {
+                /* "delta": skip pixels in x and y directions */
+                TRY_EOF( bmp_readint( f, 1, &b ) ); /* x offset */
+                TRY_EOF( bmp_readint( f, 1, &c ) ); /* y offset */
+                x += b;
+                y += c;
+            }
+            else
+            {
+                /* verbatim segment */
+                for( i = 0; i<c; i++ )
+                {
+                    TRY_EOF( bmp_readint( f, 1, &b ) );
+                    if( x>=bmpinfo.w )
+                    {
+                        x = 0;
+                        y++;
+                    }
+                    if( y>=bmpinfo.h )
+                    {
+                        break;
+                    }
+                    GM_PUT( gm, x, y, coltable[b] );
+                    x++;
+                }
+
+                if( c & 1 )
+                {
+                    /* pad input to 16-bit boundary */
+                    TRY_EOF( bmp_readint( f, 1, &b ) );
+                }
+            }
+        }
+
+        break;
+    } /* switch */
+
+    /* skip any potential junk after the data section, but don't
+     *  complain in case EOF is encountered */
+    bmp_forward( f, bmpinfo.FileSize );
+
+    free( coltable );
+    *gmp = gm;
+    return 0;
+
+eof:
+    free( coltable );
+    *gmp = gm;
+    return 1;
+
+format_error:
+try_error:
+    free( coltable );
+    free( gm );
+    if( !gm_read_error )
+    {
+        gm_read_error = "invalid bmp file";
+    }
+    return -2;
+
+std_error:
+    free( coltable );
+    free( gm );
+    return -1;
+}
+
+
+/* ---------------------------------------------------------------------- */
+
+/* write a pgm stream, either P2 or (if raw != 0) P5 format. Include
+ *  one-line comment if non-NULL. Mode determines how out-of-range
+ *  color values are converted. Gamma is the desired gamma correction,
+ *  if any (set to 2.2 if the image is to look optimal on a CRT monitor,
+ *  2.8 for LCD). Set to 1.0 for no gamma correction */
+
+int gm_writepgm( FILE* f, greymap_t* gm, char* comment, int raw, int mode, double gamma )
+{
+    int x, y, v;
+    int gammatable[256];
+
+    /* prepare gamma correction lookup table */
+    if( gamma != 1.0 )
+    {
+        gammatable[0] = 0;
+        for( v = 1; v<256; v++ )
+        {
+            gammatable[v] = (int) ( 255 * exp( log( v / 255.0 ) / gamma ) + 0.5 );
+        }
+    }
+    else
+    {
+        for( v = 0; v<256; v++ )
+        {
+            gammatable[v] = v;
+        }
+    }
+
+    fprintf( f, raw ? "P5\n" : "P2\n" );
+    if( comment && *comment )
+    {
+        fprintf( f, "# %s\n", comment );
+    }
+    fprintf( f, "%d %d 255\n", gm->w, gm->h );
+    for( y = gm->h - 1; y>=0; y-- )
+    {
+        for( x = 0; x<gm->w; x++ )
+        {
+            v = GM_UGET( gm, x, y );
+            if( mode == GM_MODE_NONZERO )
+            {
+                if( v > 255 )
+                {
+                    v = 510 - v;
+                }
+                if( v < 0 )
+                {
+                    v = 0;
+                }
+            }
+            else if( mode == GM_MODE_ODD )
+            {
+                v = mod( v, 510 );
+                if( v > 255 )
+                {
+                    v = 510 - v;
+                }
+            }
+            else if( mode == GM_MODE_POSITIVE )
+            {
+                if( v < 0 )
+                {
+                    v = 0;
+                }
+                else if( v > 255 )
+                {
+                    v = 255;
+                }
+            }
+            else if( mode == GM_MODE_NEGATIVE )
+            {
+                v = 510 - v;
+                if( v < 0 )
+                {
+                    v = 0;
+                }
+                else if( v > 255 )
+                {
+                    v = 255;
+                }
+            }
+            v = gammatable[v];
+
+            if( raw )
+            {
+                fputc( v, f );
+            }
+            else
+            {
+                fprintf( f, x == gm->w - 1 ? "%d\n" : "%d ", v );
+            }
+        }
+    }
+
+    return 0;
+}
+
+
+/* ---------------------------------------------------------------------- */
+/* output - for primitive debugging purposes only! */
+
+/* print greymap to screen */
+int gm_print( FILE* f, greymap_t* gm )
+{
+    int x, y;
+    int xx, yy;
+    int d, t;
+    int sw, sh;
+
+    sw = gm->w < 79 ? gm->w : 79;
+    sh = gm->w < 79 ? gm->h : gm->h * sw * 44 / (79 * gm->w);
+
+    for( yy = sh - 1; yy>=0; yy-- )
+    {
+        for( xx = 0; xx<sw; xx++ )
+        {
+            d = 0;
+            t = 0;
+            for( x = xx * gm->w / sw; x<(xx + 1) * gm->w / sw; x++ )
+            {
+                for( y = yy * gm->h / sh; y<(yy + 1) * gm->h / sh; y++ )
+                {
+                    d += GM_GET( gm, x, y );
+                    t += 256;
+                }
+            }
+
+            if( t )
+                fputc( "*#=- "[5 * d / t], f ); /* what a cute trick :) */
+        }
+
+        fputc( '\n', f );
+    }
+
+    return 0;
+}