lsst::afw::fits::ImageCompressionOptions Struct Reference

Options for tile compression of image pixels. More...

#include <fitsCompression.h>

Public Types
enum	CompressionAlgorithm {   NONE , GZIP , GZIP_SHUFFLE , RICE ,   PLIO }
	Compression algorithms. More...
using	Tiles = ndarray::Array<long, 1, 1>

Public Member Functions
	ImageCompressionOptions (CompressionAlgorithm algorithm_, Tiles tiles_, float quantizeLevel_=0.0)
	Custom compression.
	ImageCompressionOptions (CompressionAlgorithm algorithm_, std::vector< long > tiles_, float quantizeLevel_=0.0)
	ImageCompressionOptions (CompressionAlgorithm algorithm_, int rows=1, float quantizeLevel_=0.0)
	Compression by rows or entire image.
template<typename T >
	ImageCompressionOptions (image::Image< T > const &image)
	Default compression for a particular style of image.
template<typename T >
	ImageCompressionOptions (image::Mask< T > const &mask)
	ImageCompressionOptions (image::Image< std::int64_t > const &image)
	ImageCompressionOptions (image::Mask< std::int64_t > const &mask)
	ImageCompressionOptions (image::Image< std::uint64_t > const &image)
	ImageCompressionOptions (image::Mask< std::uint64_t > const &mask)

Public Attributes
CompressionAlgorithm	algorithm
	Compresion algorithm to use.
Tiles	tiles
	Tile size; a dimension with 0 means infinite (e.g., to specify one row: 0,1)
float	quantizeLevel
	quantization level: 0.0 = none requires use of GZIP or GZIP_SHUFFLE

Detailed Description

Options for tile compression of image pixels.

Tile compression is a feature provided by cfitsio, where contiguous parts of the image ("tiles", e.g., rows, multiple rows, blocks or the entire image) are compressed separately. The aim of this struct is to hold the parameters used to configure the compression.

Floating-point images can be losslessly compressed (quantizeLevel=0.0) using (only) the GZIP or GZIP_SHUFFLE compression algorithms, but the compression factor so achieved is modest (e.g., ~ 10% compression). Better compression factors can be achieved if floating-point images are first quantised into integer images. This can be done by cfitsio (through the quantizeLevel parameter) or through use of the ImageScalingOptions.

The Compression is specified by:

• the compression algorithm
• the tile size
• the quantization level (for quantization applied by cfitsio; for floating-point images)

Due to bugs, cfitsio may require setting the quantizeLevel to a value other than zero when compressing integer data, but in this case it should have no effect.

Definition at line 180 of file fitsCompression.h.

Member Typedef Documentation

Tiles

using lsst::afw::fits::ImageCompressionOptions::Tiles = ndarray::Array<long, 1, 1>

Definition at line 194 of file fitsCompression.h.

Member Enumeration Documentation

CompressionAlgorithm

enum lsst::afw::fits::ImageCompressionOptions::CompressionAlgorithm

Compression algorithms.

cfitsio's compression algorithms are #defines; these have a namespace.

We deliberately don't support HCOMPRESS: it doesn't appear to be useful to us (e.g., lossy) and it requires extra configuration.

Enumerator
NONE	No compression.
GZIP	Standard GZIP compression.
GZIP_SHUFFLE	GZIP compression with shuffle (most-significant byte first)
RICE	RICE compression.
PLIO	PLIO compression.

Definition at line 187 of file fitsCompression.h.

                              {
        NONE,          
        GZIP,          
        GZIP_SHUFFLE,  
        RICE,          
        PLIO,          
    };

Constructor & Destructor Documentation

ImageCompressionOptions() [1/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( CompressionAlgorithm algorithm_, Tiles tiles_, float quantizeLevel_ = 0.0 )

inlineexplicit

Custom compression.

Definition at line 201 of file fitsCompression.h.

            : algorithm(algorithm_), tiles(ndarray::copy(tiles_)), quantizeLevel(quantizeLevel_) {}

ImageCompressionOptions() [2/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( CompressionAlgorithm algorithm_, std::vector< long > tiles_, float quantizeLevel_ = 0.0 )

inlineexplicit

Definition at line 205 of file fitsCompression.h.

            : algorithm(algorithm_), tiles(ndarray::allocate(tiles_.size())), quantizeLevel(quantizeLevel_) {
        std::copy(tiles_.cbegin(), tiles_.cend(), tiles.begin());
    }

ImageCompressionOptions() [3/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( ImageCompressionOptions::CompressionAlgorithm algorithm_, int rows = 1, float quantizeLevel_ = 0.0 )

explicit

Compression by rows or entire image.

Parameters

[in]	algorithm_	Compression algorithm to use
[in]	rows	Number of rows per tile (0 = entire image)
[in]	quantizeLevel_	cfitsio quantization level

Definition at line 90 of file fitsCompression.cc.

        : algorithm(algorithm_), tiles(ndarray::allocate(MAX_COMPRESS_DIM)), quantizeLevel(quantizeLevel_) {
    tiles[0] = 0;
    tiles[1] = rows;
    for (int ii = 2; ii < MAX_COMPRESS_DIM; ++ii) tiles[ii] = 1;
}

ImageCompressionOptions() [4/9]

template<typename T >

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( image::Image< T > const & image )

inlineexplicit

Default compression for a particular style of image.

Currently defaults to NONE; change to GZIP_SHUFFLE once use of compression by default has been approved (RFC-378).

Definition at line 224 of file fitsCompression.h.

            : ImageCompressionOptions(image.getBBox().getArea() > 0 ? NONE : NONE) {}

ImageCompressionOptions() [5/9]

template<typename T >

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( image::Mask< T > const & mask )

inlineexplicit

Definition at line 227 of file fitsCompression.h.

            : ImageCompressionOptions(mask.getBBox().getArea() > 0 ? NONE : NONE) {}

ImageCompressionOptions() [6/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( image::Image< std::int64_t > const & image )

inlineexplicit

Definition at line 231 of file fitsCompression.h.

            : ImageCompressionOptions(NONE) {}

ImageCompressionOptions() [7/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( image::Mask< std::int64_t > const & mask )

inlineexplicit

Definition at line 233 of file fitsCompression.h.

: ImageCompressionOptions(NONE) {}

ImageCompressionOptions() [8/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( image::Image< std::uint64_t > const & image )

inlineexplicit

Definition at line 234 of file fitsCompression.h.

            : ImageCompressionOptions(NONE) {}

ImageCompressionOptions() [9/9]

lsst::afw::fits::ImageCompressionOptions::ImageCompressionOptions ( image::Mask< std::uint64_t > const & mask )

inlineexplicit

Definition at line 236 of file fitsCompression.h.

            : ImageCompressionOptions(NONE) {}

Member Data Documentation

algorithm

CompressionAlgorithm lsst::afw::fits::ImageCompressionOptions::algorithm

Compresion algorithm to use.

Definition at line 196 of file fitsCompression.h.

quantizeLevel

float lsst::afw::fits::ImageCompressionOptions::quantizeLevel

quantization level: 0.0 = none requires use of GZIP or GZIP_SHUFFLE

Definition at line 198 of file fitsCompression.h.

tiles

Tiles lsst::afw::fits::ImageCompressionOptions::tiles

Tile size; a dimension with 0 means infinite (e.g., to specify one row: 0,1)

Definition at line 197 of file fitsCompression.h.

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The documentation for this struct was generated from the following files:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-9.0.0/Linux64/afw/gef2f8181fd+0a71e47438/include/lsst/afw/fitsCompression.h
• /j/snowflake/release/lsstsw/stack/lsst-scipipe-9.0.0/Linux64/afw/gef2f8181fd+0a71e47438/src/fitsCompression.cc