I have a set of images that I'm combining into a single image mosaic using JAI's MosaicDescriptor. Most of the images are the same size, but some are smaller. I'd like to fill in the missing space with white - by default, the MosaicDescriptor is using black. I tried setting the the double[] background parameter to { 255 }, and that fills in the missing space with white, but it also introduces some discoloration in some of the other full-sized images. I'm open to any method - there are probably many ways to do this, but the documentation is difficult to navigate. I am considering converting any smaller images to a BufferedImage and calling setRGB() on the empty areas (though I am unsure what to use for the scansize on the batch setRGB() method). My question is essentially: What is the best way to take an image (in JAI, or BufferedImage) and fill / add padding to a certain size? Is there a way to accomplish this in the MosaicDescriptor call without side-effects? For reference, here is the code that creates the mosaic: for (int i = 0; i < images.length; i++) { images[i] = JPEGDescriptor.create(new ByteArraySeekableStream(images[i]), null); if (i != 0) { images[i] = TranslateDescriptor.create(image, (float) (width * i), null, null, null); } } RenderedOp finalImage = MosaicDescriptor.create(ops, MosaicDescriptor.MOSAIC_TYPE_OVERLAY, null, null, null, null, null);