matlab.io.fits.setCompressionType

Set image compression type

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Syntax

matlab.io.fits.setCompressionType(fptr,comptype)

Description

matlab.io.fits.setCompressionType(fptr,comptype) sets the image compression algorithm to use when writing images to the FITS file specified by fptr.

You can specify comptype as one of these values:

  • "GZIP"

  • "GZIP2"

  • "RICE"

  • "PLIO"

  • "HCOMPRESS"

  • "NOCOMPRESS"

Examples

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Open Live Script

Create a new FITS file and add an image to the file.

import matlab.io.*
data = reshape(1:256*512,[256 512]);
data = int32(data);
fptr = fits.createFile("myfile.fits");
fits.createImg(fptr,"long_img",[256 512])
fits.writeImg(fptr,data)

Set the GZIP2 compression algorithm, add another copy of the same image to the file, and then close the file.

fits.setCompressionType(fptr,"GZIP2")
fits.createImg(fptr,"long_img",[256 512])
fits.writeImg(fptr,data)
fits.closeFile(fptr)

Examine the file metadata and then delete the file.

fitsdisp("myfile.fits",Mode="full")
HDU:  1 (Primary HDU)
	SIMPLE  =                    T / file does conform to FITS standard
	BITPIX  =                   32 / number of bits per data pixel
	NAXIS   =                    2 / number of data axes
	NAXIS1  =                  512 / length of data axis 1
	NAXIS2  =                  256 / length of data axis 2
	EXTEND  =                    T / FITS dataset may contain extensions
	COMMENT   FITS (Flexible Image Transport System) format is defined in 'Astronomy
	COMMENT   and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H

HDU:  2 
	XTENSION= 'BINTABLE'           / binary table extension
	BITPIX  =                    8 / 8-bit bytes
	NAXIS   =                    2 / 2-dimensional binary table
	NAXIS1  =                    8 / width of table in bytes
	NAXIS2  =                  256 / number of rows in table
	PCOUNT  =                79619 / size of special data area
	GCOUNT  =                    1 / one data group (required keyword)
	TFIELDS =                    1 / number of fields in each row
	TTYPE1  = 'COMPRESSED_DATA'    / label for field   1
	TFORM1  = '1PB(314)'           / data format of field: variable length array
	ZIMAGE  =                    T / extension contains compressed image
	ZBITPIX =                   32 / data type of original image
	ZNAXIS  =                    2 / dimension of original image
	ZNAXIS1 =                  512 / length of original image axis
	ZNAXIS2 =                  256 / length of original image axis
	ZTILE1  =                  512 / size of tiles to be compressed
	ZTILE2  =                    1 / size of tiles to be compressed
	ZCMPTYPE= 'GZIP_2  '           / compression algorithm

delete myfile.fits

Tips

  • This function corresponds to the fits_set_compression_type function in the CFITSIO library C API.

  • To use this function, you must be familiar with the CFITSIO C interface. You can access the CFITSIO documentation at the CFITSIO website.

Extended Capabilities

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Version History

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See Also

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