GridCoverage2DReader gridReader = format.getReader(this.getInputFile(), hints);
GridCoverage2D gridCoverage = gridReader.read(null);

RenderedImage img = ImageReadDescriptor.create(ImageInputStream iis, ...);
... //calculate stripeSize

byte[] writeBuff = new byte[stripeSize*numLines];
for(nCalculatedChunksOfLines){
  Rectangle tb = new Rectangle(0, n, sample, linesInChunk );
  Raster stripe = img.getData(tb);

  ...rest of processing bypassed for debugging....
  if(stripe != null){
    continue;
  }
}