When rendering a large image, we need to handle the case of a failed texture load by backing off to a successively smaller texture. Currently we will just fail with an NPE in the renderer.

The fix for RT-21998 clamps the maximum texture size to 4096 in order to reduce the possibility of failing to load a texture due to resource limitations. However, there is no guarantee that we can allocate a 4K x 4K texture, either, so it is more of a workaround for the actual problem.