Package org.apache.sis.storage.geotiff

Class CompressedSubset

java.lang.Object

org.apache.sis.coverage.BandedCoverage

org.apache.sis.coverage.grid.GridCoverage

org.apache.sis.internal.storage.TiledGridCoverage

org.apache.sis.storage.geotiff.DataSubset

org.apache.sis.storage.geotiff.CompressedSubset

All Implemented Interfaces:

Localized

final class CompressedSubset
extends DataSubset

Raster data obtained from a compressed GeoTIFF file in the domain requested by user.

Since:

1.1

Version:

1.1

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.sis.internal.storage.TiledGridCoverage

TiledGridCoverage.AOI, TiledGridCoverage.Snapshot

Nested classes/interfaces inherited from class org.apache.sis.coverage.grid.GridCoverage

GridCoverage.Evaluator

Field Summary

Fields

Modifier and Type	Field	Description
private final int	afterLastBand	Number of sample values to skip for reaching end-of-row after reading the last value of the first pixel in a row.
private final int	beforeFirstBand	Number of sample values to skip before to read the first value of the first pixel in a row.
private Inflater	inflater	The inflater, created when reading the first tile and discarded after reading the last tile.
private final int	samplesPerChunk	Number of sample values that compose a chunk (pixel or sample) in the GeoTIFF file.
private final long	scanlineStride	Number of sample values to skip for moving to the next row of a tile in the GeoTIFF file.
private final int[]	skipAfterChunks	Number of sample values to skip after a chunk has been read, or null if none.

Fields inherited from class org.apache.sis.storage.geotiff.DataSubset

numBanks, source, sourcePixelStride, targetPixelStride

Fields inherited from class org.apache.sis.internal.storage.TiledGridCoverage

BIDIMENSIONAL, colors, fillValue, includedBands, model, X_DIMENSION, Y_DIMENSION

Fields inherited from class org.apache.sis.coverage.grid.GridCoverage

gridGeometry

Constructor Summary

Constructors

Constructor	Description
CompressedSubset(DataCube source, TiledGridResource.Subset subset)	Creates a new data subset.

Method Summary

Modifier and Type	Method	Description
(package private) final Closeable	createInflater()	Returns the object to close for releasing inflater resources.
private static int	pixelCount(long[] lower, long[] upper, int[] subsampling, int i)	Computes the number of pixels to read in dimension i.
(package private) Raster	readSlice(long[] offsets, long[] byteCounts, long[] lower, long[] upper, int[] subsampling, Point location)	Reads a two-dimensional slice of the data cube from the given input channel.
private void	releaseInflater()	Invoked after the last tile has been read, or after an exception has been thrown during the reading process.
private static boolean	startsWithZeros(int[] skipAfterChunks, int m)	Returns true if all array elements except the last one are zeros.

Methods inherited from class org.apache.sis.storage.geotiff.DataSubset

fillRemainingRows, getBankCapacity, getDataType, getIdentifier, getLocale, input, readTiles

Methods inherited from class org.apache.sis.internal.storage.TiledGridCoverage

getPixelsPerElement, getSubsampling, getTileSize, render

Methods inherited from class org.apache.sis.coverage.grid.GridCoverage

createConvertedValues, evaluator, forConvertedValues, getCoordinateReferenceSystem, getEnvelope, getGridGeometry, getSampleDimensions, toString, toTree

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

scanlineStride

private final long scanlineStride

Number of sample values to skip for moving to the next row of a tile in the GeoTIFF file. This is not necessarily the same scanline stride than for the tiles created by this class.

beforeFirstBand

private final int beforeFirstBand

Number of sample values to skip before to read the first value of the first pixel in a row. The first pixel is at column index 0; subsampling offset is not included in this calculation.

afterLastBand

private final int afterLastBand

Number of sample values to skip for reaching end-of-row after reading the last value of the first pixel in a row. For computing the actual number of sample values to skip, the number of sample values read or skipped before the last pixel must be subtracted.

skipAfterChunks

private final int[] skipAfterChunks

Number of sample values to skip after a chunk has been read, or null if none. In this class, a "chunk" is a sample value or a complete pixel, depending on samplesPerChunk (note that the definition of "chunk" can be expanded to an entire row by the Inflater class). The skipAfterChunks array is used in a cyclic way:

• Skip skipAfterChunks[0] sample values between chunk 0 and chunk 1.
• Skip skipAfterChunks[1] sample values between chunk 1 and chunk 2.
• etc. When we reach the array end, continue at skipAfterChunks[0].
• When we start a new row, unconditionally restart at skipAfterChunks[0].

More generally, skip skipAfterChunks[x % skipAfterChunks.length] sample values after chunk at the zero-based column index x.

samplesPerChunk

private final int samplesPerChunk

Number of sample values that compose a chunk (pixel or sample) in the GeoTIFF file. The value of this field can be:

• 1 if a chunk is a sample value.
• DataSubset.sourcePixelStride if a chunk is a full pixel.
• Any intermediate value if some optimizations have been applied, for example for taking advantage of consecutive indices in TiledGridCoverage.includedBands.

This value shall always be a divisor of DataSubset.targetPixelStride.

inflater

private transient Inflater inflater

The inflater, created when reading the first tile and discarded after reading the last tile.

See Also:

• releaseInflater()

Constructor Details

CompressedSubset

CompressedSubset(DataCube source,
 TiledGridResource.Subset subset)
          throws DataStoreException

Creates a new data subset. All parameters should have been validated by ImageFileDirectory.validateMandatoryTags() before this call. This constructor should be invoked inside a synchronized block.

Parameters:

source - the resource which contain this DataSubset.

subset - description of the owner subset to cover.

rasters - potentially shared cache of rasters read by this DataSubset.

Throws:

ArithmeticException - if the number of tiles overflows 32 bits integer arithmetic.

DataStoreException

Method Details

startsWithZeros

private static boolean startsWithZeros(int[] skipAfterChunks,
 int m)

Returns true if all array elements except the last one are zeros. A true value means that all sample values in a pixel are consecutive.

Parameters:

m - skipAfterChunks.length - 1. Shall be greater than zero.

pixelCount

private static int pixelCount(long[] lower,
 long[] upper,
 int[] subsampling,
 int i)

Computes the number of pixels to read in dimension i. The arguments given to this method are the ones given to the readSlice(…) method.

readSlice

Raster readSlice(long[] offsets,
 long[] byteCounts,
 long[] lower,
 long[] upper,
 int[] subsampling,
 Point location)
          throws IOException,
DataStoreException

Reads a two-dimensional slice of the data cube from the given input channel.

Overrides:

readSlice in class DataSubset

Parameters:

offsets - position in the channel where tile data begins, one value per bank.

byteCounts - number of bytes for the compressed tile data, one value per bank.

lower - (x, y) coordinates of the first pixel to read relative to the tile.

upper - (x, y) coordinates after the last pixel to read relative to the tile.

subsampling - (sx, sy) subsampling factors.

location - pixel coordinates in the upper-left corner of the tile to return.

Returns:

a single tile decoded from the GeoTIFF file.

Throws:

IOException - if an I/O error occurred.

DataStoreException - if a logical error occurred.

See Also:

• DataCube.canReadDirect(TiledGridResource.Subset)

createInflater

final Closeable createInflater()

Returns the object to close for releasing inflater resources. This method is invoked in a synchronized block before the first call to readSlice(…).

Overrides:

createInflater in class DataSubset

releaseInflater

private void releaseInflater()
                      throws IOException

Invoked after the last tile has been read, or after an exception has been thrown during the reading process. This method releases any resources used by the inflater.

Throws:

IOException