Hello Adam
Please feel free to ask as you want, no problem :)
The Cache class is for any kind of object associated to an identifier.
For example Coordinate Reference Systems (CRS) are often specified as
the primary key value in the EPSG database. For example "EPSG:4326"
stands for a geographic CRS using the WGS84 datum, and "EPSG:3395"
stands for a Mercator projection using the WGS84 datum. SIS will provide
a factory creating CRS objects from an EPSG code. But if the same EPSG
code is specified many time, we want to return the existing instance.
This will happen often since GIS applications typically contain
thousands of geometries using the same CRS.
This applies also to metadata, for example getting a CI_Citation object
from an ISBN code. This could apply to images where the identifier could
be the absolute path name, etc. In the later case, since images can be
large, we need to measure the cost of keeping those objects in a cache.
About caching of map tile, maybe the Cache class could be used for that,
but we way also use something more specialized. We could take
inspiration from the TileCache interface from Java Advanced Imaging [1]
for instance.
Martin
[1]
http://download.java.net/media/jai/javadoc/1.1.3/jai-apidocs/javax/media/jai/TileCache.html
Le 14/10/12 09:35, Adam Estrada a écrit :
Martin,
I am catching up on emails from a long week of conferences and a little
vacation time so please forgive me if this response sounds redundant or at
all dense. Is your cache class to be used as an actual map cache to store
and retrieve map tiles? It kind of sounds like that as we often test to see
if cached tiles have been changed by counting pixels and their values
before generating new ones. If nothing has changed, leave them alone,
right? Can this class be used like that or is that the intent?
Adam
