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@@ -279,47 +279,47 @@ The GRASS GIS raster format is architecture independent and portable between
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<h3>Raster compression</h3>
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<!-- keep in sync with raster/r.compress/r.compress.html -->
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-GRASS raster maps are by default ZLIB compressed. If the environment
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-variable <tt>GRASS_INT_ZLIB</tt> exists and has the value 0, newly
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-generated compressed integer (CELL type) raster maps will be compressed
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-using RLE compression instead of ZLIB.
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+
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+All GRASS GIS raster map types are by default ZLIB compressed, i.e. using
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+ZLIB's deflate algorithm. Through the environment variable
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+<tt>GRASS_COMPRESSOR</tt> the compression method can be set to RLE, ZLIB,
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+LZ4, or BZIP2.
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+<p>
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+Integer (CELL type) raster maps can be compressed with RLE if
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+the environment variable <tt>GRASS_INT_ZLIB</tt> exists and is set to value
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+0. However, this is not recommended.
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<p>
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Floating point (FCELL, DCELL) raster maps never use RLE compression;
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they are either compressed with ZLIB, LZ4, BZIP2 or are uncompressed.
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-<p>
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-The compression method for raster maps is by default ZLIB's deflate
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-algorithm. The compression method can be set with the environment
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-variable GRASS_COMPRESSOR which can be set to RLE, ZLIB, LZ4, or BZIP2.
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<dl>
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<dt><strong>RLE</strong></dt>
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<dd><b>DEPRECATED</b> Run-Length Encoding, poor compression ratio but
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-fast. Kept for backwards compatibility to read raster maps created with
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-GRASS 6. Only used for raster maps of type CELL. FCELL and DCELL maps
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-are never and have never been compressed with RLE.</dd>
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+fast. It is kept for backwards compatibility to read raster maps
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+created with GRASS 6. It is only used for raster maps of type CELL.
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+FCELL and DCELL maps are never and have never been compressed with RLE.
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+</dd>
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<dt><strong>ZLIB</strong></dt>
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<dd>ZLIB's deflate is the default compression method for all raster
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-maps. GRASS 7 uses by default 1 as ZLIB compression level which is the
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+maps. GRASS GIS 7 uses by default 1 as ZLIB compression level which is the
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best compromise betweeen speed and compression ratio, also when
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compared to other available compression methods. Valid levels are in
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the range [1, 9] and can be set with the environment variable
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-GRASS_ZLIB_LEVEL.</dd>
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+<tt>GRASS_ZLIB_LEVEL</tt>.</dd>
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<dt><strong>LZ4</strong></dt>
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<dd>LZ4 is a very fast compression method, about as fast as no
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-compression. The compression ration is generally higher than for RLE.
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-Decompression is also very fast. LZ4 is recommended if disk space is
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-not a limiting factor, but some sving on disk space is welcomed without
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-increasing processing speed. The compression ratio of LZ4 is generally
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-better than for RLE but worse than for ZLIB.</dd>
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+compression. Decompression is also very fast. The compression ratio is
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+generally higher than for RLE but worse than for ZLIB. LZ4 is
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+recommended if disk space is not a limiting factor.</dd>
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<dt><strong>BZIP2</strong></dt>
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-<dd>BZIP2 can provide compression ratios much higher than for the other
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+<dd>BZIP2 can provide compression ratios much higher than the other
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methods, but only for large raster maps (> 10000 columns). For large
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raster maps, disk space consumption can be reduced by 30 - 50% when
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using BZIP2 instead of ZLIB's deflate. BZIP2 is the slowest compression
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and decompression method. However, if reading from / writing to a
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storage device is the limiting factor, BZIP2 compression can speed up
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raster map processing. Be aware that for smaller raster maps, BZIP2
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-compression ratio can be worse than for other compression methods.</dd>
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+compression ratio can be worse than other compression methods.</dd>
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</dl>
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<p>
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Markus Neteler