Hi Simon,
Thanks for the code and the description, that's great!
- Don
On Aug 24, 2004, at 6:53 AM, Simon Bowen wrote:
> Don,
>
>
>
> Heard that you were integrating for next version of OpenMap, I have
> made some more changed to the mif package, the changes were made to
> address specific memory and performance issues that I was having with
> my application.
>
>
>
> This submission may not be for everyone as I have taken some fairly
> radical approaches to improve memory and performance, please chop and
> change this as you please for submission. I have fully tested this
> with OpenMap 4.5 (That's what I'm currently using), I have run a quick
> test of the package against OpenMap 4.6 and it seems to work OK,
> however Don you may want to make some changes.
>
>
>
> There are still some issues with the code (see below), I was going to
> hold off submission until they were fixed, but as it's integration
> time, and I have been getting personal emails for people regarding the
> mif package I thought I would get it out now. The problems I've listed
> below are not that major, they do not really have an impact for my
> application, using large mif files in WGS84 around Europe.
>
>
>
> Changes Made
>
> --------------------
>
> Created new Graphic objects for MIF Graphics, these graphic objects
> use the java2d api directly and bypass the OMGraphics, I have done
> this to save on memory and improve rendering speed. The downside to
> this is that once the graphics are rendered to the buffer you can no
> longer interact with them as you would be able to with an OMGraphics
> object.
>
>
>
> Implemented some cache for AWT Colours, the previous version would
> make a new colour object every time it needed one, so you could end up
> with say 1000 copies of a particular colour in memory at anyone time,
> the AWTCache eliminates this so that only 1 instance of any given
> color will be in memory at anyone time.
>
>
>
> For performance of reading the MIF data, I have implemented a
> mechanism in the MIFLoader, when a MIF file is loaded for the first
> time the MIF data is parsed and all the appropriate graphic objects
> are attached to the MIF Layer, these objects are then serialized to
> disk in the same directory as the original mif file, a CheckSum of the
> original MIF file is also serialized. Subsequent attempts to load the
> MIF file will check for the existence of the serialized version of the
> MIF file, ensure the CheckSum still matches the original MIF data
> file, if so the serialized MIF layer is then unserialized and used, if
> the CheckSum does not match the serialized object is deleted and
> recreated from the MIF file.
>
>
>
> For performance of rendering the MIF Layer, the graphics get rendered
> to an offscreen buffer, that get blitted to the screen when ready, the
> paint method will just keep blitting the buffer every time
> paint(Graphics) is called, when a reprojection occurs the Buffer is
> cleared down and regerenated. I have put this in place as paint method
> was getting called many times even though the projection hadn't
> changed, just blitting the buffer every time gives a significant
> improvement when moving windows around, turning layers on/off etc..
>
>
>
> Rendering of Region borders fixed so that the appear as they do in
> MapInfo Professional
>
>
>
> Note that there is a file com.bbn.openmap.CheckSum, this is some code
> from Sun that I have modified, Don you should move this to what ever
> package you think is appropriate.
>
>
>
>
>
> There are still some issues with this code however:-
>
> --------------------------------------------------------------------
>
> 1. Looks like there is a issue projecting or rendering points that
> intersect the -180/+180 line (Maybe some one can fix this, I can
> provide test data if needed)
>
>
>
> 2. The MIFLoader parser does not fully comply with the MapInfo MIF
> specification, however it will work for 99% of files
>
>
>
> 3. There is a problem in the Coordinate System header validation in
> the MIFLoader class, where it can wrongly mistake an invalid
> coordinate system as being valid
>
>
>
> 4. There is a bug in some version of JDK 1.4.1 where if the JVM (on
> Windows) does not have read permission for a file, any attempt to open
> it as a stream will result in the file being deleted (Yes, I know this
> is quite odd). See
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4804606. I
> recommend using JDK 1.4.2, however it will still work ok with 1.4.1
> unless you have certain permissions on your data files.
>
>
>
> 5. There may be some other issues that I have missed, please fix and
> mail them to the community, or let me know about them and I will fix
> them when I have time.
>
>
>
> I am open to anyone who has any questions regarding this, I will try
> to answer all your questions as soon as I can, don't be surprised if
> it takes me a few days to reply as I'm very busy at the moment!
>
>
>
> Happy MIF'ing!
>
>
>
>
>
> Simon
>
>
>
>
>
>
> <mif.zip>
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Don Dietrick, dietrick_at_bbn.com
BBN Technologies, Cambridge, MA
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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Received on Tue Aug 24 2004 - 13:47:24 EDT