Working with "large" images

[brians08]

So I just downloaded diit and tried it out.  I am apparently pushing this stego stuff to the limit with a half meg. message file because I quickly found out that the picutures from my 5 megapixl camera are just barely large enough to "cover" a 0.5M message. 
The problem I run into is that diit or the JVM appears to have trouble allocating memory because when I use these two inputs I always get an error message about a -XMX heap setting and not enough memory. 
I googled the xmx heap thing and can't find any instructions about increasing the JVM's memory space. 
Any suggestions?

[KathrynH]

Java is a bit of a memory hog.  The default heap space is quite small, so to increase it when running DIIT you have to add the -Xmx flag at the command line (case is important).  For example, if you have 256MB of physical memory (RAM) in your pc, then you would run DIIT with:
java -jar -Xmx256m diit-1-5.jar

if you had 512MB of physical memory then you would use:
java -jar -Xmx512m diit-1-5.jar

I have 1GB of memory in my pc, and I get away with running it with -Xmx512m with most of my digital camera pics (although I could use -Xmx1024m if I so chose). 


Also, you can hide your large message in a smaller image by changing the algorithm settings - like make it write from 1-to-2 instead of 1-to-1 bits.  Each time you up the writeable bit range you add 1/8th of the image space to write in.  That is, if you change it to 1-to-4 then you will find that half the image is overwritten with your message, so a 1MB Bitmap file would actually support your 0.5MB message.  The writeable bit range will affect how well your message is hidden as well as how much you can hide.  Just remember, you have to use the same algorithm settings to extract your message, so if you hide with a 1-to-4 bit range, you must try to extract your message with that setting too or else it will just return garbage.