Image from bytes streams

Hello!

I'm trying to get an array of bytes from graphic images generated by
R. Here, you can see my Java code:

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Process p = Runtime.getRuntime().exec("C:/Arquivos de
programas/R/rw1090/bin/Rterm.exe --no-save");

DataOutputStream output = new DataOutputStream(new
BufferedOutputStream(p.getOutputStream()));

DataInputStream input = new DataInputStream(new
BufferedInputStream(p.getInputStream()));

// output.writeBytes("pie(c(50,30,20))"); //Pie graphic
output.writeBytes("plot(1,1)"); // Plot graphic
output.flush();

input.readFully(new byte[200]); // Here I read the "image" bytes.
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That's the problem: when I use Pie graphic, I got some bytes. However,
when I use the Plot graphic, I got the same bytes! So, I suppose that
my program does not read the bytes from the generated graphic from R.

Is it possible to get the bytes from the generated graphic? How can I
get these bytes?

Sorry about my english. I'm brazilian! :)

First, thank you very much for the answers...

I have used the png() function before for generate the image and then
capture its bytes.

My big problem is that my program reads the image before that its
complete by the png() function. For instance, my graphic image has
1000Kb. When R saves it into the hard disk, my Java program reads the
file before the save operation completes (500Kb for example). So, I
got only a part of the file and hence the image... :(

One solution is read the image and search for a byte which represents
the end of the file, but it depends on the image format...

So, how can I discover that R image save operation stored the complete
file into the hard disk?

My big problem is that my program reads the image before that its
complete by the png() function. For instance, my graphic image has
1000Kb. When R saves it into the hard disk, my Java program reads the
file before the save operation completes (500Kb for example). So, I
got only a part of the file and hence the image... :(

One solution is read the image and search for a byte which represents
the end of the file, but it depends on the image format...