RenderedOp crop = JAI.create("Crop", pb, JAIContext.noCacheHint);
// Format retiles the image
// TODO: this needs better understanding, can we just specify the layout for Crop?
pb = new ParameterBlock();
pb.addSource(crop);
pb.add(back.getSampleModel().getDataType());
RenderingHints formatHints = new RenderingHints(JAI.KEY_IMAGE_LAYOUT, new ImageLayout(back));
formatHints.add(JAIContext.noCacheHint);
RenderedOp formatted = JAI.create("Format", pb, formatHints);