Losing Color During Image Conversion Using JAI

I've been using Java Advanced Imaging to convert tiff images to jpeg. The code I'm using is pretty simple, and I'll include it below:

Java Code: private static void convertImage(File tiff_src, File jpg_dest)
{
if (tiff_src == null || !tiff_src.exists()) throw new IllegalArgumentException();
try
{
SeekableStream stream = null;

[code]...

The problem when I run this code is that during conversion, the decoder or encoder seems to drop a good deal of black. I'd like to include examples, but the tiff images are about 30 MB...I've tried configuring the decode parameters, as well as the encode parameters, but like I said, somewhere during conversion I drop a good deal of the black from the image.