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#include	<u.h>
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#include	<libc.h>
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#include	<bio.h>
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#include	"sky.h"
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static	void	dodecode(Biobuf*, Pix*, int, int, uchar*);
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static	long	getlong(uchar*);
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int	debug;
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Img*
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dssread(char *file)
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{
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	int nx, ny, scale, sumall;
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	Pix  *p, *pend;
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	uchar buf[21];
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	Biobuf *bp;
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	Img *ip;
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	if(debug)
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		Bprint(&bout, "reading %s\n", file);
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	bp = Bopen(file, OREAD);
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	if(bp == 0)
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		return 0;
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	if(Bread(bp, buf, sizeof(buf)) != sizeof(buf) ||
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	   buf[0] != 0xdd || buf[1] != 0x99){
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		werrstr("bad format");
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		return 0;
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	}
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	nx = getlong(buf+2);
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	ny = getlong(buf+6);
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	scale = getlong(buf+10);
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	sumall = getlong(buf+14);
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	if(debug)
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		fprint(2, "%s: nx=%d, ny=%d, scale=%d, sumall=%d, nbitplanes=%d,%d,%d\n",
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			file, nx, ny, scale, sumall, buf[18], buf[19], buf[20]);
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	ip = malloc(sizeof(Img) + (nx*ny-1)*sizeof(int));
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	if(ip == 0){
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		Bterm(bp);
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		werrstr("no memory");
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		return 0;
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	}
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	ip->nx = nx;
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	ip->ny = ny;
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	dodecode(bp, ip->a, nx, ny, buf+18);
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	ip->a[0] = sumall;	/* sum of all pixels */
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	Bterm(bp);
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	if(scale > 1){
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		p = ip->a;
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		pend = &ip->a[nx*ny];
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		while(p < pend)
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			*p++ *= scale;
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	}
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	hinv(ip->a, nx, ny);
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	return ip;
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}
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static
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void
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dodecode(Biobuf *infile, Pix  *a, int nx, int ny, uchar *nbitplanes)
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{
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	int nel, nx2, ny2, bits, mask;
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	Pix *aend, px;
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	nel = nx*ny;
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	nx2 = (nx+1)/2;
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	ny2 = (ny+1)/2;
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	memset(a, 0, nel*sizeof(*a));
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	/*
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	 * Initialize bit input
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	 */
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	start_inputing_bits();
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	/*
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	 * read bit planes for each quadrant
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	 */
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	qtree_decode(infile, &a[0],          ny, nx2,  ny2,  nbitplanes[0]);
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	qtree_decode(infile, &a[ny2],        ny, nx2,  ny/2, nbitplanes[1]);
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	qtree_decode(infile, &a[ny*nx2],     ny, nx/2, ny2,  nbitplanes[1]);
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	qtree_decode(infile, &a[ny*nx2+ny2], ny, nx/2, ny/2, nbitplanes[2]);
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	/*
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	 * make sure there is an EOF symbol (nybble=0) at end
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	 */
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	if(input_nybble(infile) != 0){
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		fprint(2, "dodecode: bad bit plane values\n");
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		exits("format");
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	}
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	/*
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	 * get the sign bits
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	 */
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	aend = &a[nel];
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	mask = 0;
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	bits = 0;;
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	for(; a<aend; a++) {
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		if(px = *a) {
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			if(mask == 0) {
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				mask = 0x80;
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				bits = Bgetc(infile);
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			}
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			if(mask & bits)
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				*a = -px;
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			mask >>= 1;
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		}
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	}
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}
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static
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long	getlong(uchar *p)
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{
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	return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
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}