Re: OMBitMap ...

Hi Pradeep,

There isn't a height and width restriction on OMBitmaps, but you do have
to be careful about the byte array that is used for one. The OMBitmap
is based on an X bitmap, not a Windows bmp file. Each bit of the bytes
corresponds to a pixel. If the height and/or width of the bitmap isn't
a multiple of 8, you have to round up the number of bytes used so that
the excess bits are covered in that extra byte for the row.

So, for a 4x4 bitmap, you need:

ooooxxxx|ooooxxxx|ooooxxxx|ooooxxxx -> 4 bytes, where x's are the bits
being used for the bitmap ( and whether they are 1 or 0 dictates either
foreground or background color), and o's are the leftover bits (they are
ignored). The '|' are byte boundaries.

The bits, per byte, look like they are used in reverse order because
they are - least significant bit, per byte, is used in that order.

For a 6x6 bitmap:

ooxxxxxx|ooxxxxxx|ooxxxxxx|ooxxxxxx|ooxxxxxx|ooxxxxxx

for a 10x10 bitmap

xxxxxxxx|ooooooxx|xxxxxxxx|ooooooxx|xxxxxxxx|ooooooxx|xxxxxxxx|ooooooxx|xxxxxxxx|
ooooooxx|xxxxxxxx|ooooooxx|xxxxxxxx|ooooooxx|xxxxxxxx|ooooooxx|xxxxxxxx|ooooooxx|
xxxxxxxx|ooooooxx

The DemoLayer bitmap is confusing because it uses a multiple of 8 as a
side, and the subtleties are hidden.

I'm going to add the above explaination to the OMBitmap documentation.

Hope this helps,

Don

On Wednesday, August 29, 2001, at 09:40 AM, PRADEEP RAMACHANDRAN wrote:

> Hello,
>
> Are there minimum height,width restrictions while
> creating an OMBitMap.
>
> Changing the OMBitMap in the Demo Layer to use a
> 4 x 4 pixel height/width throws up an
> ArrayIndexOutOfBoundsException ...
>
> Regards,
> Pradeep.
>
>
>
>
>
> Get 250 color business cards for FREE!
> http://businesscards.lycos.com/vp/fastpath/
>
> --
> [To unsubscribe to this list send an email to "majdart@bbn.com"
> with the following text in the BODY of the message "unsubscribe
> openmap-users"]
>

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Donald F. Dietrick, dietrick@bbn.com
BBN Technologies, 10 Moulton Street, Cambridge, MA 02138
617.873.3031 FAX 2794
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
[To unsubscribe to this list send an email to "majdart@bbn.com"
with the following text in the BODY of the message "unsubscribe openmap-users"]