nom.tam.fits.header.Compression Maven / Gradle / Ivy
package nom.tam.fits.header;
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/**
* The following keywords are defined by the compression convention for use in
* the header of the FITS binary table extension to describe the structure of
* the compressed image.
*/
public enum Compression implements IFitsHeader {
/**
* (required keyword) This keyword must have the logical value T. The value
* field of this keyword shall be ’T’ to indicate that the FITS binary table
* extension contains a compressed BINTABLE, and that logically this
* extension should be interpreted as a tile-compressed binary table.
*/
ZTABLE(HDU.ANY, VALUE.LOGICAL, ""),
/**
* (required keyword) This keyword must have the logical value T. It
* indicates that the FITS binary table extension contains a compressed
* image and that logically this extension should be interpreted as an image
* and not as a table.
*/
ZIMAGE(HDU.ANY, VALUE.LOGICAL, ""),
/**
* (required keyword) The value field of this keyword shall contain a
* character string giving the name of the algorithm that must be used to
* decompress the image. Currently, values of GZIP 1 , GZIP 2 , RICE 1 ,
* PLIO 1 , and HCOMPRESS 1 are reserved, and the corresponding algorithms
* are described in a later section of this document . The value RICE ONE is
* also reserved as an alias for RICE 1 .
*/
ZCMPTYPE(HDU.ANY, VALUE.STRING, ""),
/**
* (required keyword) The value field of this keyword shall contain an
* integer that gives the value of the BITPIX keyword in the uncompressed
* FITS image. 1
*/
ZBITPIX(HDU.ANY, VALUE.INTEGER, "", Standard.BITPIX),
/**
* (required keyword) The value field of this keyword shall contain an
* integer that gives the value of the NAXIS keyword in the uncompressed
* FITS image.
*/
ZNAXIS(HDU.ANY, VALUE.INTEGER, "", Standard.NAXIS),
/**
* (required keywords) The value field of these keywords shall contain a
* positive integer that gives the value of the NAXISn keywords in the
* uncompressed FITS image.
*/
ZNAXISn(HDU.ANY, VALUE.INTEGER, "", Standard.NAXISn),
/**
* (optional keywords) The value of these indexed keywords (where n ranges
* from 1 to ZNAXIS ) shall contain a positive integer representing the
* number o f pixels along axis n of the compression tiles. Each tile of
* pixels is compressed separately and stored in a row of a variable-length
* vector column in the binary table. The size of each image dimension
* (given by ZNAXISn ) is not required to be an integer multiple of ZTILEn,
* and if it is not, then the last tile along that dimension of the image
* will contain fewer image pixels than the other tiles. If the ZTILEn
* keywords are not present then the default ’row by row’ tiling will be
* assumed such that ZTILE1 = ZNAXIS1 , and the value of all the other
* ZTILEn keywords equals 1. The compressed image tiles are stored in the
* binary table in t he same order that the first pixel in each tile appears
* in the FITS image; the tile containing the first pixel in the image
* appears in the first row of the table, and the tile containing the last
* pixel in the image appears in the last row of the binary table.
*/
ZTILEn(HDU.ANY, VALUE.INTEGER, ""),
/**
* (optional keywords) These pairs of optional array keywords (where n is an
* integer index number starting with 1) supply the name and value,
* respectively, of any algorithm-specific parameters that are needed to
* compress o r uncompress the image. The value of ZVALn may have any valid
* FITS datatype. The order of the compression parameters may be
* significant, and may be defined as part of the description of the
* specific decompression algorithm.
*/
ZNAMEn(HDU.ANY, VALUE.STRING, ""),
/**
* (optional keywords) These pairs of optional array keywords (where n is an
* integer index number starting with 1) supply the name and value,
* respectively, of any algorithm-specific parameters that are needed to
* compress o r uncompress the image. The value of ZVALn may have any valid
* FITS datatype. The order of the compression parameters may be
* significant, and may be defined as part of the description of the
* specific decompression algorithm.
*/
ZVALn(HDU.ANY, VALUE.ANY, ""),
/**
* (optional keyword) Used to record the name of the image compression
* algorithm that was used to compress the optional null pixel data mask.
* See the “Preserving undefined pixels with lossy compression” section for
* more details.
*/
ZMASKCMP(HDU.ANY, VALUE.STRING, ""),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy of the original FITS file when the image is
* uncompressed.preserves the original SIMPLE keyword.may only be used if
* the original uncompressed image was contained in the primary array of the
* FITS file.
*/
ZSIMPLE(HDU.PRIMARY, VALUE.LOGICAL, "", Standard.SIMPLE),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy o f the original FITS file when the image is
* uncompressed.preserves the original XTENSION keyword.may only be used if
* the original uncompressed image was contained in in IMAGE extension.
*/
ZTENSION(HDU.ANY, VALUE.STRING, "", Standard.XTENSION),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy of the original FITS file when the image is
* uncompressed.preserves the original EXTEND keyword.may only be used if
* the original uncompressed image was contained in the primary array of the
* FITS file.
*/
ZEXTEND(HDU.PRIMARY, VALUE.LOGICAL, "", Standard.EXTEND),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy o f the original FITS file when the image is
* uncompressed.preserves the original BLOCKED keyword.may only be used if
* the original uncompressed image was contained in the primary array of the
* FITS file,
*/
@Deprecated ZBLOCKED(HDU.PRIMARY, VALUE.LOGICAL, "", Standard.BLOCKED),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy o f the original FITS file when the image is
* uncompressed.preserves the original PCOUNT keyword.may only be used if
* the original uncompressed image was contained in in IMAGE extension.
*/
ZPCOUNT(HDU.EXTENSION, VALUE.INTEGER, "", Standard.PCOUNT),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy o f the original FITS file when the image is
* uncompressed.preserves the original GCOUNT keyword.may only be used if
* the original uncompressed image was contained in in IMAGE extension.
*/
ZGCOUNT(HDU.EXTENSION, VALUE.INTEGER, "", Standard.GCOUNT),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy o f the original FITS file when the image is
* uncompressed.preserves the original CHECKSUM keyword.
*/
ZHECKSUM(HDU.ANY, VALUE.STRING, "", Checksum.CHECKSUM),
/**
* The following optional keyword is defined to store a verbatim copy of the
* the value and comment field of the corresponding keyword in the original
* uncompressed FITS image. These keywords can be used to reconstruct an
* identical copy o f the original FITS file when the image is
* uncompressed.preserves the original DATASUM
*/
ZDATASUM(HDU.ANY, VALUE.STRING, "", Checksum.DATASUM),
/**
* (optional keyword) This keyword records the name of the algorithm that
* was used to quantize floating-point image pixels into integer values
* which are then passed to the compression algorithm.
*/
ZQUANTIZ(HDU.ANY, VALUE.STRING, ""),
/**
* (optional keyword) The value field of this keyword shall contain an
* integer that gives the seed value for the random dithering pattern that
* was used when quantizing the floating-point pixel values. The value may
* range from 1 to 100.00, inclusive.
*/
ZDITHER0(HDU.ANY, VALUE.INTEGER, ""),
/**
* When using the quantization method to compress floating-point images,
* this header is used to store the integer value that represents undefined
* pixels (if any) in the scaled integer pixel values. These pixels have an
* IEEE NaN value (Not a Number) in the uncompressed floating-point image.
* The recommended value for ZBLANK is -2147483648 (the largest negative
* 32-bit integer).
*/
ZBLANK(HDU.ANY, VALUE.INTEGER, ""),
/**
* The value field of this keyword shall contain an integer representing the
* number of rows of data from the original binary table that are contained
* in each tile of the compressed table. The number of rows in the last tile
* may be less than in the previous tiles. Note that if the entire table is
* compressed as a single tile, then the compressed table will only contains
* a single row, and the ZTILELEN and ZNAXIS2 keywords will have the same
* value.
*/
ZTILELEN(HDU.ANY, VALUE.INTEGER, ""),
/**
* The value field of these keywords shall contain the character string
* values of the corresponding TFORMn keywords that defines the data type of
* column n in the original uncompressed FITS table.
*/
ZFORMn(HDU.ANY, VALUE.STRING, "", Standard.TFORMn),
/**
* The value field of these keywords shall contain a charac- ter string
* giving the mnemonic name of the algorithm that was used to compress
* column n of the table. The current allowed values are GZIP_1, GZIP_2, and
* RICE_1, and the corresponding algorithms
*/
ZCTYPn(HDU.ANY, VALUE.STRING, "");
/**
* This is the simplest option in which no dithering is performed. The
* floating-point pixels are simply quantized using Eq. 1. This option
* should be assumed if the ZQUANTIZ keyword is not present in the header of
* the compressed floating-point image.
*/
public static final String ZQUANTIZ_NO_DITHER = "NO_DITHER";
/**
* It should be noted that an image that is quantized using this technique
* can stil l be unquantized using the simple linear scaling function given
* by Eq. 1. The only side effect in this ca se is to introduce slightly
* more noise in the image than if the full subtractive dithering algorith m
* were applied.
*/
public static final String ZQUANTIZ_SUBTRACTIVE_DITHER_1 = "SUBTRACTIVE_DITHER_1";
/**
* This dithering algorithm is identical to the SUBTRACTIVE DITHER 1
* algorithm described above, ex- cept that any pixels in the floating-point
* image that are equa l to 0.0 are represented by the reserved value
* -2147483647 in the quantized integer array. When the i mage is
* subsequently uncompressed and unscaled, these pixels are restored to
* their original va lue of 0.0. This dithering option is useful if the
* zero-valued pixels have special significance to the da ta analysis
* software, so that the value of these pixels must not be dithered.
*/
public static final String ZQUANTIZ_SUBTRACTIVE_DITHER_2 = "SUBTRACTIVE_DITHER_2";
/**
* Gzip is the compression algorithm used in the free GN U software utility
* of the same name. It was created by Jean-loup Gailly and Mark Adler and
* is based on the DEFLATE algorithm, which is a combination of LZ77 and
* Huffman coding. DEFLATE was intended as a replacement for LZW and other
* patent-encumbered data compression algor ithms which, at the time,
* limited the usability of compress and other popular archivers. Furt her
* information about this compression technique is readily available on the
* Internet. The gzip alg orithm has no associated parameters that need to
* be specified with the ZNAMEn and ZVALn keywords.
*/
public static final String ZCMPTYPE_GZIP_1 = "GZIP_1";
/**
* If ZCMPTYPE = ’GZIP 2’ then the bytes in the array of image pixel values
* are shuffled in to decreasing order of significance before being
* compressed with the gzip algorithm. In other words, bytes are shuffled so
* that the most significant byte of every pixel occurs first, in order,
* followed by the next most significant byte, and so on for every byte.
* Since the most significan bytes of the pixel values often have very
* similar values, grouping them together in this way often achieves better
* net compression of the array. This is usually especially effective when
* compressing floating-point arrays.
*/
public static final String ZCMPTYPE_GZIP_2 = "GZIP_2";
/**
* If ZCMPTYPE = ’RICE 1’ then the Rice algorithm is used to compress and
* uncompress the image pixels. The Rice algorithm (Rice, R. F., Yeh, P.-S.,
* and Miller, W. H. 1993, in Proc. of the 9th AIAA Computing in Aerospace
* Conf., AIAA-93-4541-CP, American Institute of Aeronautics and
* Astronautics) is simple and very fast, compressing or decompressing 10 7
* pixels/sec on modern workstations. It requires only enough memory to hold
* a single block of 16 or 32 pixels at a time. It codes the pixels in small
* blocks and so is able to adapt very quickly to changes in the input image
* statistics (e.g., Rice has no problem handling cosmic rays, bright stars,
* saturated pixels, etc.).
*/
public static final String ZCMPTYPE_RICE_1 = "RICE_1";
/**
* If ZCMPTYPE = ’PLIO 1’ then the IRAF PLIO (Pixel List) algorithm is used
* to compress and uncompress the image pixels. The PLIO algorithm was
* developed to store integer-valued image masks in a compressed form.
* Typical uses of image masks are to segment images into regions, or to
* mark bad pixels. Such masks often have large regions of constant value
* hence are highly compressible. The compression algorithm used is based on
* run-length encoding, with the ability to dynamically follow level changes
* in the image, allowing a 16-bit encoding to be used regardless of the
* image depth. The worst case performance occurs when successive pixels
* have different values. Even in this case the encoding will only require
* one word (16 bits) per mask pixel, provided either the delta intensity
* change between pixels is usually less than 12 bits, or the mask
* represents a zero floored step function of constant height. The worst
* case cannot exceed npix*2 words provided the mask depth is 24 bits or
* less.
*/
public static final String ZCMPTYPE_PLIO_1 = "PLIO_1";
/**
* Hcompress is an the image compression package written by Richard L. White
* for use at the Space Telescope Science Institute. Hcompress was used to
* compress the STScI Digitized Sky Survey and has also been used to
* compress the preview images in the Hubble Data Archive. Briefly, the
* method used is:
* 1. a wavelet transform called the H-transform (a Haar transform
* generalized to two dimensions), followed by
* 2. quantization that discards noise in the image while retaining the
* signal on all scales, followed by 10
* 3. quadtree coding of the quantized coefficients.
* The technique gives very good compression for astronomical images and is
* relatively fast. The calculations are carried out using integer
* arithmetic and a re entirely reversible. Consequently, the program can be
* used for either lossy or lossless compression , with no special approach
* needed for the lossless case (e.g. there is no need for a file of
* residuals .)
*/
public static final String ZCMPTYPE_HCOMPRESS_1 = "HCOMPRESS_1";
/**
* alternative name for 'RICE 1'
*/
public static final String ZCMPTYPE_RICE_ONE = "RICE_ONE";
/**
* compression algorithm that specifies that the data is uncompressed.
*/
public static final String ZCMPTYPE_NOCOMPRESS = "NOCOMPRESS";
/**
* Each row of this variable-length column contains the byte st ream that is
* generated as a result of compressing the corresponding image tile. The
* datatype o f the column (as given by the TFORMn keyword) will generally
* be either ’1PB’, ’1PI’ , or ’1PJ’ (or the equivalent ’1Q’ format),
* depending on whether the compression algorithm ge nerates an output
* stream of 8-bit bytes, 16-bit integers, or 32-bit integers, respectively.
*/
public static final String COMPRESSED_DATA_COLUMN = "COMPRESSED_DATA";
/**
* When using the quantization method to compress floating-poi nt images
* that is described in Section 4, it sometimes may not be possible to
* quantize some o f the tiles (e.g., if the range of pixels values is too
* large or if most of the pixels have the sam e value and hence the
* calculated RMS noise level in the tile is close to zero). There also may
* be other rare cases where the nominal compression algorithm can not be
* applied to certain tiles. In these cases, one may use an alternate
* technique in which the raw pixel values are loss lessly compressed with
* the GZIP algorithm and the resulting byte stream is stored in the GZIP
* COMPRESSED DATA column (with a ’1PB’ or ’1QB’ variable-length array
* column format). The corresponding COMPRESSED DATA column for these tiles
* must contain a null pointer.
*/
public static final String GZIP_COMPRESSED_DATA_COLUMN = "GZIP_COMPRESSED_DATA";
/**
* Use of this column is no longer recommended, but it may exist i n older
* compressed image files that were created before support for the GZIP
* COMPRESSED DATA column (describe above) was added to this convention in
* May 2011. This variable length co lumn contains the uncompressed pixels
* for any tiles that cannot be compressed with the norma l method.
*/
public static final String UNCOMPRESSED_DATA_COLUMN = "UNCOMPRESSED_DATA";
/**
* When using the quantization method to compress floating-point images that
* is described in Section 4, this column is used to store the integer value
* that represents undefined pixels (if any) in the scaled integer pixel
* values. These pixels have an IEEE NaN value (Not a Number) in the
* uncompressed floating-point image. The recommended value for ZBLANK is
* -2147483648 (the largest negative 32-bit integer).
*/
public static final String ZBLANK_COLUMN = "ZBLANK";
/**
* name of the column containing the quant zero value.
*/
public static final String ZZERO_COLUMN = "ZZERO";
/**
* name of the column containing the quant scale value.
*/
public static final String ZSCALE_COLUMN = "ZSCALE";
/**
*
* The null pixels in integer images are flagged by a reserved BLANK value
* and will be preserved if a lossless compression algorithm is used. If the
* image is compressed with a lossy algorithm, however (e.g., H-Compress
* with a scale factor greater than 1), then some other technique must be
* used to identify the null pixels in the image.
*
*
* The recommended method of recording the null pixels when a lossy
* compression algorithm is used is to create an integer data mask with the
* same dimensions as the image tile. Set the null pixels to 1 and all the
* other pixels to 0, then compress the mask array using a lossless
* algorithm such as PLIO or GZIP. Store the compressed byte stream in a
* variable-length array column called ’NULL PIXEL MASK’ in the row
* corresponding to that image tile. The ZMASKCMP keyword should be used to
* record the name of the algorithm used to compress the data mask (e.g.,
* RICE 1). The data mask array pixels will be assumed to have the shortest
* integer datatype that is supported by the compression algorithm (i.e.,
* usually 8-bit bytes).
*
*
* When uncompressing the image tile, the software must check if the
* corresponding compressed data mask exists with a length greater than 0,
* and if so, then uncompress the mask and set the corresponding undefined
* pixels in the image array to the appropriate value (as given by the BLANK
* keyword).
*
*/
public static final String NULL_PIXEL_MASK_COLUMN = "NULL_PIXEL_MASK_COLUMN";
/**
* The number of 8-bit bytes in each original integer pixel value.
*/
public static final String BYTEPIX = "BYTEPIX";
/**
* The blocksize parameter for the rise algorithm.
*/
public static final String BLOCKSIZE = "BLOCKSIZE";
/**
* The integer scale parameter determines the amount of compression. Scale =
* 0 or 1 leads to lossless compression, i.e. the decompressed image has
* exactly the same pixel values as the original image. If the scale factor
* is greater than 1 then the compression is lossy: the decompressed image
* will not be exactly the same as the original.
*/
public static final String SCALE = "SCALE";
/**
* At high compressions factors the decompressed image begins to appear
* blocky because of the way information is discarded. This blockiness is
* greatly reduced, producing more pleasing images, if the image is smoothed
* slightly during decompression. When done properly, the smoothing will not
* affect any quantitative photometric or astrometric measurements derived
* from the compressed image. Of course, the smoothing should never be
* applied when the image has been losslessly compressed with a scale factor
* (defined above) of 0 or 1.
*/
public static final String SMOOTH = "SMOOTH";
@SuppressWarnings("CPD-START")
private final IFitsHeader key;
private final IFitsHeader uncompressedKey;
Compression(HDU hdu, VALUE valueType, String comment) {
this(hdu, valueType, comment, null);
}
Compression(HDU hdu, VALUE valueType, String comment, IFitsHeader uncompressedKey) {
this.key = new FitsHeaderImpl(name(), IFitsHeader.SOURCE.HEASARC, hdu, valueType, comment);
this.uncompressedKey = uncompressedKey;
}
@Override
public String comment() {
return this.key.comment();
}
public IFitsHeader getUncompressedKey() {
return this.uncompressedKey;
}
@Override
public HDU hdu() {
return this.key.hdu();
}
@Override
public String key() {
return this.key.key();
}
@Override
public IFitsHeader n(int... number) {
return this.key.n(number);
}
@Override
public SOURCE status() {
return this.key.status();
}
@Override
@SuppressWarnings("CPD-END")
public VALUE valueType() {
return this.key.valueType();
}
}
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