3.4 Image Compression

Image Compression

There are many situations in which you need to compress or decompress images. For example, to save space in an archive, or to save network transfer time. The Compress class provides methods to compress and decompress images using one of the following compression types:

Keyword	Description
UNIX_COMPRESS	UNIX style compress, as with the UNIX compress(1) command
H_COMPRESS	H-compress (lossy compression, reduces the amount of data)
ULDA_COMPRESS	ULDA compressed FITS file
GZIP_COMPRESS	Compress using the GNU gzip command.

The following example compresses and then decompresses the file "test.fits" using the H-compress compression type:

 
if (c.compress("test.fits", "test.hfits", Compress::H_COMPRESS) != 0) 
		return ERROR;

if (c.decompress("test.hfits", "test.fits", Compress::H_COMPRESS) != 0)
		return ERROR

See the man page Compress(3) for more details.