Ch-8.Image-compression.rar_in_tifs2cv.m

/*=================================================================== * unravel.c * Decodes a variable length coded bit sequence (a vector of * 16-bit integers) using a binary sort from the MSB to the LSB * (across word boundaries) based on a transition table. *==================================================================*/ #include "mex.h" void unravel(uint16_T *hx, double *link, double *x, double xsz, int hxsz) { int i = 15, j = 0, k = 0, n = 0; /* Start at root node, 1st */ /* hx bit and x element */ while (xsz - k) { /* Do until x is filled */ if (*(link + n) > 0) { /* Is there a link? */ if ((*(hx + j) >> i) & 0x0001) /* Is bit a 1? */ n = *(link + n); /* Yes, get new node */ else n = *(link + n) - 1; /* It's 0 so get new node */ if (i) i--; else {j++; i = 15;} /* Set i, j to next bit */ if (j > hxsz) /* Bits left to decode? */ mexErrMsgTxt("Out of code bits ???"); } else { /* It must be a leaf node */ *(x + k++) = - *(link + n); /* Output value */ n = 0; } /* Start over at root */ } if (k == xsz - 1) /* Is one left over? */ *(x + k++) = - *(link + n); } void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { double *link, *x, xsz; uint16_T *hx; int hxsz; /* Check inputs for reasonableness */ if (nrhs != 3) mexErrMsgTxt("Three inputs required."); else if (nlhs > 1) mexErrMsgTxt("Too many output arguments."); /* Is last input argument a scalar? */ if(!mxIsDouble(prhs[2]) || mxIsComplex(prhs[2]) || mxGetN(prhs[2]) * mxGetM(prhs[2]) != 1) mexErrMsgTxt("Input XSIZE must be a scalar."); /* Create input matrix pointers and get scalar */ hx = (uint16_T *) mxGetData(prhs[0]); link = (double *) mxGetData(prhs[1]); xsz = mxGetScalar(prhs[2]); /* returns DOUBLE */ /* Get the number of elements in hx */ hxsz = mxGetM(prhs[0]); /* Create 'xsz' x 1 output matrix */ plhs[0] = mxCreateDoubleMatrix(xsz, 1, mxREAL); /* Get C pointer to a copy of the output matrix */ x = (double *) mxGetData(plhs[0]); /* Call the C subroutine */ unravel(hx, link, x, xsz, hxsz); }