slimfits
Version:
Package for loading data stored in FITS data format
305 lines • 11.3 kB
JavaScript
var Rice = /** @class */ (function () {
function Rice() {
}
Rice.fits_rdecomp = function (c, array, nblock) {
var nonzero_count = Rice.getNonzeroCount();
var cPointer = 0;
var fsbits = 5;
var fsmax = 25;
var bbits = (1 << fsbits) | 0;
var lastpix = (new DataView(c.buffer, c.byteOffset)).getInt32(0, false);
cPointer += 4;
var b = c[cPointer++]; /* bit buffer */
var nbits = 8; /* number of bits remaining in b */
for (var i = 0; i < array.length;) {
/* get the FS value from first fsbits */
nbits -= fsbits;
while (nbits < 0) {
b = (b << 8) | c[cPointer++];
nbits += 8;
}
var fs = (b >> nbits) - 1;
b &= (1 << nbits) - 1;
/* loop over the next block */
var imax = i + nblock;
if (imax > array.length) {
imax = array.length;
}
if (fs < 0) {
/* low-entropy case, all zero differences */
for (; i < imax; i++) {
array[i] = lastpix;
}
}
else if (fs === fsmax) {
/* high-entropy case, directly coded pixel values */
for (; i < imax; i++) {
var k = bbits - nbits;
var diff = b << k;
for (k -= 8; k >= 0; k -= 8) {
b = c[cPointer++];
diff |= b << k;
}
if (nbits > 0) {
b = c[cPointer++];
diff |= b >> (-k);
b &= (1 << nbits) - 1;
}
else {
b = 0;
}
/*
* undo mapping and differencing
* Note that some of these operations will overflow the
* unsigned int arithmetic -- that's OK, it all works
* out to give the right answers in the output file.
*/
if ((diff & 1) === 0) {
diff = diff >> 1;
}
else {
diff = ~(diff >> 1);
}
array[i] = diff + lastpix;
lastpix = array[i];
}
}
else {
/* normal case, Rice coding */
for (; i < imax; i++) {
/* count number of leading zeros */
while (b === 0) {
nbits += 8;
b = c[cPointer++];
}
var nzero = nbits - nonzero_count[b];
nbits -= nzero + 1;
/* flip the leading one-bit */
b ^= 1 << nbits;
/* get the FS trailing bits */
nbits -= fs;
while (nbits < 0) {
b = (b << 8) | (c[cPointer++]);
nbits += 8;
}
var diff = (nzero << fs) | (b >> nbits);
b &= (1 << nbits) - 1;
/* undo mapping and differencing */
if ((diff & 1) === 0) {
diff = diff >> 1;
}
else {
diff = ~(diff >> 1);
}
array[i] = diff + lastpix;
lastpix = array[i];
}
}
}
};
Rice.fits_rdecomp_short = function (c, array, nblock) {
var nonzero_count = Rice.getNonzeroCount();
var cPointer = 0;
var fsbits = 4;
var fsmax = 14;
var bbits = 1 << fsbits;
var lastpix = (new DataView(c.buffer, c.byteOffset)).getInt16(0, false);
cPointer += 2;
var b = c[cPointer++]; /* bit buffer */
var nbits = 8; /* number of bits remaining in b */
for (var i = 0; i < array.length;) {
/* get the FS value from first fsbits */
nbits -= fsbits;
while (nbits < 0) {
b = (b << 8) | c[cPointer++];
nbits += 8;
}
var fs = (b >> nbits) - 1;
b &= (1 << nbits) - 1;
/* loop over the next block */
var imax = i + nblock;
if (imax > array.length) {
imax = array.length;
}
if (fs < 0) {
/* low-entropy case, all zero differences */
for (; i < imax; i++) {
array[i] = lastpix;
}
}
else if (fs === fsmax) {
/* high-entropy case, directly coded pixel values */
for (; i < imax; i++) {
var k = bbits - nbits;
var diff = b << k;
for (k -= 8; k >= 0; k -= 8) {
b = c[cPointer++];
diff |= b << k;
}
if (nbits > 0) {
b = c[cPointer++];
diff |= b >> (-k);
b &= (1 << nbits) - 1;
}
else {
b = 0;
}
/*
* undo mapping and differencing
* Note that some of these operations will overflow the
* unsigned int arithmetic -- that's OK, it all works
* out to give the right answers in the output file.
*/
if ((diff & 1) === 0) {
diff = diff >> 1;
}
else {
diff = ~(diff >> 1);
}
array[i] = diff + lastpix;
lastpix = array[i];
}
}
else {
/* normal case, Rice coding */
for (; i < imax; i++) {
/* count number of leading zeros */
while (b === 0) {
nbits += 8;
b = c[cPointer++];
}
var nzero = nbits - nonzero_count[b];
nbits -= nzero + 1;
/* flip the leading one-bit */
b ^= 1 << nbits;
/* get the FS trailing bits */
nbits -= fs;
while (nbits < 0) {
b = (b << 8) | c[cPointer++];
nbits += 8;
}
var diff = (nzero << fs) | (b >> nbits);
b &= (1 << nbits) - 1;
/* undo mapping and differencing */
if ((diff & 1) === 0) {
diff = diff >> 1;
}
else {
diff = ~(diff >> 1);
}
array[i] = diff + lastpix;
lastpix = array[i];
}
}
}
};
Rice.fits_rdecomp_byte = function (c, array, nblock) {
var nonzero_count = Rice.getNonzeroCount();
var cPointer = 0;
var fsbits = 3;
var fsmax = 6;
var bbits = 1 << fsbits;
var lastpix = c[0];
cPointer += 1;
var b = c[cPointer++]; /* bit buffer */
var nbits = 8; /* number of bits remaining in b */
for (var i = 0; i < array.length;) {
/* get the FS value from first fsbits */
nbits -= fsbits;
while (nbits < 0) {
b = (b << 8) | c[cPointer++];
nbits += 8;
}
var fs = (b >> nbits) - 1;
b &= (1 << nbits) - 1;
/* loop over the next block */
var imax = i + nblock;
if (imax > array.length) {
imax = array.length;
}
if (fs < 0) {
/* low-entropy case, all zero differences */
for (; i < imax; i++) {
array[i] = lastpix;
}
}
else if (fs === fsmax) {
/* high-entropy case, directly coded pixel values */
for (; i < imax; i++) {
var k = bbits - nbits;
var diff = b << k;
for (k -= 8; k >= 0; k -= 8) {
b = c[cPointer++];
diff |= b << k;
}
if (nbits > 0) {
b = c[cPointer++];
diff |= b >> (-k);
b &= (1 << nbits) - 1;
}
else {
b = 0;
}
/*
* undo mapping and differencing
* Note that some of these operations will overflow the
* unsigned int arithmetic -- that's OK, it all works
* out to give the right answers in the output file.
*/
if ((diff & 1) === 0) {
diff = diff >> 1;
}
else {
diff = ~(diff >> 1);
}
array[i] = diff + lastpix;
lastpix = array[i];
}
}
else {
/* normal case, Rice coding */
for (; i < imax; i++) {
/* count number of leading zeros */
while (b === 0) {
nbits += 8;
b = c[cPointer++];
}
var nzero = nbits - nonzero_count[b];
nbits -= nzero + 1;
/* flip the leading one-bit */
b ^= 1 << nbits;
/* get the FS trailing bits */
nbits -= fs;
while (nbits < 0) {
b = (b << 8) | c[cPointer++];
nbits += 8;
}
var diff = (nzero << fs) | (b >> nbits);
b &= (1 << nbits) - 1;
/* undo mapping and differencing */
if ((diff & 1) === 0) {
diff = diff >> 1;
}
else {
diff = ~(diff >> 1);
}
array[i] = diff + lastpix;
lastpix = array[i];
}
}
}
};
Rice.getNonzeroCount = function () {
var arr = new Uint8Array(256);
var k = 1;
for (var i = 1; i <= 8; i++) {
for (var j = 0; j < Math.pow(2, i - 1); j++) {
arr[k++] = i;
}
}
return arr;
};
return Rice;
}());
export { Rice };
//# sourceMappingURL=Rice.js.map