New answers tagged geotools
This could be related to any number of factors, such as RAM, CPU etc on your machine. But the most likely is that your GeoTiff isn't optimised for speed. Have you added overviews? is your image tiled or does GeoTools have to read the whole image each time to draw a small subset. I recommend you read the excellent GeoServer on Steroids talk from GeoSolutions ...
I would check the tests in github, here. That said I would say you should look into optimized (big)tiff support. Check these slides which are made for GeoServer but still usable for your case I believe. http://goo.gl/74XUPq Simone.
Top 50 recent answers are included