/* spctoppm.c - read a compressed Spectrum file and produce a portable pixmap
**
** Copyright (C) 1991 by Steve Belczyk and Jef Poskanzer
**
** 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 software is provided "as is" without express or
** implied warranty.
*/

#include "ppm.h"

#define ROWS 200
#define COLS 320
#define MAXVAL 7

static void DoBitmap ( FILE* const ifp );
static void DoChar (int const n, char const c);
static void DoColormap ( FILE* const ifp );

static char screen[ROWS*COLS/2];
static short sscreen[ROWS*COLS/4];
static pixel pal[ROWS][48];
static long int colormap_length, bitmap_length;

int
main(int argc, char* argv[]) {

    FILE* ifp;
    char c1, c2;
    pixel* pixelrow;
    pixel* pP;
    int row, col;


    ppm_init( &argc, argv );

    /* Check args. */
    if ( argc > 2 )
        pm_usage( "[spcfile]" );

    if ( argc == 2 )
        ifp = pm_openr( argv[1] );
    else
        ifp = stdin;

    /* Check SPC file header. */
    c1 = getc( ifp );
    c2 = getc( ifp );

    if ( ( c1 != 'S' ) || ( c2 != 'P' ) )
        pm_error( "not a Spectrum picture" );

    /* Skip reserved bytes. */
    getc( ifp );
    getc( ifp );

    /* Get length of bitmap data. */
    (void) pm_readbiglong( ifp, &bitmap_length );

    /* and colormap */
    (void) pm_readbiglong( ifp, &colormap_length );

    /* Process bitmap. */
    DoBitmap( ifp );

    /* Process colormap. */
    DoColormap( ifp );

    pm_close( ifp );

    /* Write the PPM file. */
    ppm_writeppminit( stdout, COLS, ROWS, (pixval) MAXVAL, 0 );
    pixelrow = ppm_allocrow( COLS );

    for ( row = 0; row < ROWS; ++row )
        {
        for ( col = 0, pP = pixelrow; col < COLS; ++col, ++pP )
            {
            int c, ind, b, plane, x1;

            /* Compute pixel value. */
            ind = ( 80 * row ) + ( ( col >> 4 ) << 2 );
            b = 0x8000 >> (col & 0xf);
            c = 0;
            for ( plane = 0; plane < 4; ++plane )
                if ( b & sscreen[ind+plane] )
                    c |= (1 << plane);

            /* Compute palette index. */
            x1 = 10 * c;
            if ( c & 1 )
                x1 -= 5;
            else
                ++x1;
            if ( ( col >= x1 ) && ( col < ( x1 + 160 ) ) )
                c += 16;
            if ( col >= ( x1 + 160 ) )
                c += 32;

            /* Store the proper color. */
            *pP = pal[row][c];
            }
        ppm_writeppmrow( stdout, pixelrow, COLS, (pixval) MAXVAL, 0 );
        }

    pm_close( stdout );

    exit( 0 );
    }

static void
DoBitmap( FILE* ifp ) {

    int i;
    long int count, data;
    signed char h, c;

    /* Zero out first scan line. */
    for ( i = 0; i < 160; ++i )
        screen[i] = 0;

    /* 'count' counts number of input bytes. */
    count = 0;

    /* 'data' counts just data bytes. */
    data = 0;

    while ( count < bitmap_length )
        {
        /* Get next record header. */
        h = getc( ifp );
        ++count;

        if ( ( h >= 0 ) && ( count < bitmap_length ) )
            {
            for ( i = 0; i <= h; ++i )
                {
                c = getc( ifp );
                ++count;
                DoChar( data, c );
                ++data;
                }
            }
        else if ( ( h < 0 ) && ( count < bitmap_length ) )
            {
            c = getc( ifp );
            ++count;

            for ( i = 0; i < ( 2 - h ); ++i )
                {
                DoChar( data, c );
                ++data;
                }
            }
    }

    /* Convert the char version of the screen to short. */
    for ( i = 0; i < ROWS*COLS/4; ++i )
        sscreen[i] = ( screen[i<<1] << 8 ) + ( 0xff & screen[(i<<1)+1] );
    }

static void
DoChar( const int n, const char c )
    {
    int i;

    /* Compute screen index. */
    i = 160 + 2 * ( n / 7960 ) + 8 * ( ( n % 7960 ) / 2 ) + ( n & 1 );
    screen[i] = c;
    }

static void
DoColormap( FILE* ifp) {

    int i, j, b;
    short mask;

    /* Clear first three palettes. */
    for ( j = 0; j < 48; ++j )
        PPM_ASSIGN( pal[0][j], 0, 0, 0 );

    /* Read the palettes. */
    for ( i = 1; i < ROWS; ++i )
        for ( j = 0; j < 3; ++j )
            {
            (void) pm_readbigshort( ifp, &mask );
            for ( b = 0; b < 15; ++b )
                if ( mask & ( 1 << b ) )
                    {
                    short k;
                    (void) pm_readbigshort( ifp, &k );
                    PPM_ASSIGN( pal[i][(j*16)+b],
                        ( k & 0x700 ) >> 8,
                        ( k & 0x070 ) >> 4,
                        ( k & 0x007 ) );
                    }
            }
    }



