Subversion Repositories planix.SVN

#include	<u.h>

#include	<libc.h>

#include	<bio.h>

#include	"sky.h"

static void	qtree_expand(Biobuf*, uchar*, int, int, uchar*);

static void	qtree_copy(uchar*, int, int, uchar*, int);

static void	qtree_bitins(uchar*, int, int, Pix*, int, int);

static void	read_bdirect(Biobuf*, Pix*, int, int, int, uchar*, int);

void

qtree_decode(Biobuf *infile, Pix *a, int n, int nqx, int nqy, int nbitplanes)

{

	int log2n, k, bit, b, nqmax;

	int nx,ny,nfx,nfy,c;

	int nqx2, nqy2;

	unsigned char *scratch;

	/*

	 * log2n is log2 of max(nqx,nqy) rounded up to next power of 2

	 */

	nqmax = nqy;

	if(nqx > nqmax)

		nqmax = nqx;

	log2n = log(nqmax)/LN2+0.5;

	if (nqmax > (1<<log2n))

		log2n++;

	/*

	 * allocate scratch array for working space

	 */

	nqx2 = (nqx+1)/2;

	nqy2 = (nqy+1)/2;

	scratch = (uchar*)malloc(nqx2*nqy2);

	if(scratch == nil) {

		fprint(2, "qtree_decode: insufficient memory\n");

		exits("memory");

	}

	/*

	 * now decode each bit plane, starting at the top

	 * A is assumed to be initialized to zero

	 */

	for(bit = nbitplanes-1; bit >= 0; bit--) {

		/*

		 * Was bitplane was quadtree-coded or written directly?

		 */

		b = input_nybble(infile);

		if(b == 0) {

			/*

			 * bit map was written directly

			 */

			read_bdirect(infile, a, n, nqx, nqy, scratch, bit);

		} else

		if(b != 0xf) {

			fprint(2, "qtree_decode: bad format code %x\n",b);

			exits("format");

		} else {

			/*

			 * bitmap was quadtree-coded, do log2n expansions

			 * read first code

			 */

			scratch[0] = input_huffman(infile);

			/*

			 * do log2n expansions, reading codes from file as necessary

			 */

			nx = 1;

			ny = 1;

			nfx = nqx;

			nfy = nqy;

			c = 1<<log2n;

			for(k = 1; k<log2n; k++) {

				/*

				 * this somewhat cryptic code generates the sequence

				 * n[k-1] = (n[k]+1)/2 where n[log2n]=nqx or nqy

				 */

				c = c>>1;

				nx = nx<<1;

				ny = ny<<1;

				if(nfx <= c)

					nx--;

				else

					nfx -= c;

				if(nfy <= c)

					ny--;

				else

					nfy -= c;

				qtree_expand(infile, scratch, nx, ny, scratch);

			}

			/*

			 * copy last set of 4-bit codes to bitplane bit of array a

			 */

			qtree_bitins(scratch, nqx, nqy, a, n, bit);

		}

	}

	free(scratch);

}

/*

 * do one quadtree expansion step on array a[(nqx+1)/2,(nqy+1)/2]

 * results put into b[nqx,nqy] (which may be the same as a)

 */

static

void

qtree_expand(Biobuf *infile, uchar *a, int nx, int ny, uchar *b)

{

	uchar *b1;

	/*

	 * first copy a to b, expanding each 4-bit value

	 */

	qtree_copy(a, nx, ny, b, ny);

	/*

	 * now read new 4-bit values into b for each non-zero element

	 */

	b1 = &b[nx*ny];

	while(b1 > b) {

		b1--;

		if(*b1 != 0)

			*b1 = input_huffman(infile);

	}

}

/*

 * copy 4-bit values from a[(nx+1)/2,(ny+1)/2] to b[nx,ny], expanding

 * each value to 2x2 pixels

 * a,b may be same array

 */

static

void

qtree_copy(uchar *a, int nx, int ny, uchar *b, int n)

{

	int i, j, k, nx2, ny2;

	int s00, s10;

	/*

	 * first copy 4-bit values to b

	 * start at end in case a,b are same array

	 */

	nx2 = (nx+1)/2;

	ny2 = (ny+1)/2;

	k = ny2*(nx2-1) + ny2-1;	/* k   is index of a[i,j] */

	for (i = nx2-1; i >= 0; i--) {

		s00 = 2*(n*i+ny2-1);	/* s00 is index of b[2*i,2*j] */

		for (j = ny2-1; j >= 0; j--) {

			b[s00] = a[k];

			k -= 1;

			s00 -= 2;

		}

	}

	/*

	 * now expand each 2x2 block

	 */

	for(i = 0; i<nx-1; i += 2) {

		s00 = n*i;				/* s00 is index of b[i,j] */

		s10 = s00+n;				/* s10 is index of b[i+1,j] */

		for(j = 0; j<ny-1; j += 2) {

			b[s10+1] =  b[s00]     & 1;

			b[s10  ] = (b[s00]>>1) & 1;

			b[s00+1] = (b[s00]>>2) & 1;

			b[s00  ] = (b[s00]>>3) & 1;

			s00 += 2;

			s10 += 2;

		}

		if(j < ny) {

			/*

			 * row size is odd, do last element in row

			 * s00+1, s10+1 are off edge

			 */

			b[s10  ] = (b[s00]>>1) & 1;

			b[s00  ] = (b[s00]>>3) & 1;

		}

	}

	if(i < nx) {

		/*

		 * column size is odd, do last row

		 * s10, s10+1 are off edge

		 */

		s00 = n*i;

		for (j = 0; j<ny-1; j += 2) {

			b[s00+1] = (b[s00]>>2) & 1;

			b[s00  ] = (b[s00]>>3) & 1;

			s00 += 2;

		}

		if(j < ny) {

			/*

			 * both row and column size are odd, do corner element

			 * s00+1, s10, s10+1 are off edge

			 */

			b[s00  ] = (b[s00]>>3) & 1;

		}

	}

}

/*

 * Copy 4-bit values from a[(nx+1)/2,(ny+1)/2] to b[nx,ny], expanding

 * each value to 2x2 pixels and inserting into bitplane BIT of B.

 * A,B may NOT be same array (it wouldn't make sense to be inserting

 * bits into the same array anyway.)

 */

static

void

qtree_bitins(uchar *a, int nx, int ny, Pix *b, int n, int bit)

{

	int i, j;

	Pix *s00, *s10;

	Pix px;

	/*

	 * expand each 2x2 block

	 */

	for(i=0; i<nx-1; i+=2) {

		s00 = &b[n*i];			/* s00 is index of b[i,j] */

		s10 = s00+n;			/* s10 is index of b[i+1,j] */

		for(j=0; j<ny-1; j+=2) {

			px = *a++;

			s10[1] |= ( px     & 1) << bit;

			s10[0] |= ((px>>1) & 1) << bit;

			s00[1] |= ((px>>2) & 1) << bit;

			s00[0] |= ((px>>3) & 1) << bit;

			s00 += 2;

			s10 += 2;

		}

		if(j < ny) {

			/*

			 * row size is odd, do last element in row

			 * s00+1, s10+1 are off edge

			 */

			px = *a++;

			s10[0] |= ((px>>1) & 1) << bit;

			s00[0] |= ((px>>3) & 1) << bit;

		}

	}

	if(i < nx) {

		/*

		 * column size is odd, do last row

		 * s10, s10+1 are off edge

		 */

		s00 = &b[n*i];

		for(j=0; j<ny-1; j+=2) {

			px = *a++;

			s00[1] |= ((px>>2) & 1) << bit;

			s00[0] |= ((px>>3) & 1) << bit;

			s00 += 2;

		}

		if(j < ny) {

			/*

			 * both row and column size are odd, do corner element

			 * s00+1, s10, s10+1 are off edge

			 */

			s00[0] |= ((*a>>3) & 1) << bit;

		}

	}

}

static

void

read_bdirect(Biobuf *infile, Pix *a, int n, int nqx, int nqy, uchar *scratch, int bit)

{

	int i;

	/*

	 * read bit image packed 4 pixels/nybble

	 */

	for(i = 0; i < ((nqx+1)/2) * ((nqy+1)/2); i++) {

		scratch[i] = input_nybble(infile);

	}

	/*

	 * insert in bitplane BIT of image A

	 */

	qtree_bitins(scratch, nqx, nqy, a, n, bit);

}