Changes between Version 70 and Version 71 of Grass7/RasterLib

Timestamp:

May 15, 2015, 3:42:13 AM (9 years ago)

Author:

neteler

Comment:

+NULL file format

Grass7/RasterLib

@@ -44 +44 @@
     * The tile size in the G3d library is variable and can be set when a new map is created. The program r3.retile can be used to store raster3d maps with different tile size. Additionally a function is implemented to compute the optimal tile dimension for a given max size in bytes.
   * However, row-oriented storage has the advantage that you can easily skip entire rows when downsampling. Using e.g. 64x1 "tiles" would provide both optimisations, but at the expense of reduced compression, as you need a pointer (8 bytes) for each tile, and the compression has to be restarted for each tile.
- * Merge NULL file into main data array.
+ * Merge NULL file into main data array:
    * This approach is implemented in the G3d library
 
+
+Notes about NULL file format
+ * Current cell_misc/null file size in GRASS GIS 7: The size of the cell_misc/<mapname>/null file depends only upon the number of rows and columns, not the data. It's one bit (null/non-null) for each cell, rounded to an integral number of bytes per row (i.e. the number of columns is rounded up to the nearest multiple of 8).
+ * Compression idea: see #2349
 === Directory structure ===